$299 Gibson tube amp - Made in USA!

That's just what I was going to suggest...maybe the OT primary wire colors (or the secondary) were wrong from the factory (wouldn't be the first time), and with no NFB originally, it would not be detected as a problem at the factory...

Excellent idea TNO and Reddart. you guys may be onto something.

I've been rereading all these great posts, and I wanted to ask what you meant by "crippling" the second stage with a lower gain tube like I had done. How's that translate in layman's terms ;) I'm new to the world of amp tweaking, and I ain't too educated on it...yet :)
droo

I thought "cripple" was a layman's term.

The point is that using a lower gain tube, lowers the gain of the first preamp stage, which seems to be a good thing with these amps, but it also lowers the gain of the second stage, which isn't necessary or ideal.

Leaving the 12AX7 in place and removing the cathode bypass cap on the first stage, reduces the gain of that stage, but leaves the 2nd stage as is.

All right, then if "cripple" is layman's terms....I need ding dong terms ;)

So then by leaving the 2nd stage as is, we keep the 2nd stage doing "it's job"...could that be the thinner sound I am experiencing with the lower gain tube? Lower gains in both stages gives me a wimpy signal, lower the first only and I can still feed the 2nd it's necessary signal and keep the meat, so to speak?

droo

This thread is INCREDIBLE! being a complete novice, I am reading and re-reading everything so when I rip my dirty-thirty apart to make it into a tube amp I will only electrocute myself twice, as opposed to the normal 5 time a nubbie would...

Seriously, thanks you guys! This is invaluable.

I did the changes in the order that they were posted, so I guess that my amp just has some weird little gremlin that likes to squeal living under the board. Ha I have put a 12AT7 preamp tube in and will play it a bit this morning to see how it affects my tone and overall sound. I will probably reinstall the .1 cap off of the volume pot to the reamp as well as remove the 22pf bypass cap and give it a test ride. Your help and suggestions are greatly appreciated.


Could be a lose/bad solder joint...especially on a ground connection.

All right, then if "cripple" is layman's terms....I need ding dong terms ;)

So then by leaving the 2nd stage as is, we keep the 2nd stage doing "it's job"...could that be the thinner sound I am experiencing with the lower gain tube? Lower gains in both stages gives me a wimpy signal, lower the first only and I can still feed the 2nd it's necessary signal and keep the meat, so to speak?

droo

There you go. And Brent is on to it too.

Gain is multiplicative, not additive. So when you reduce the gain of both stages 30% each, you're really knocking the signal down. Much more than you need to to get it to clean up a bit.

Yeah, guys, an amp like this is pretty easy to follow, so it make a great learning platform. And it's fun! ;-)

Thanks so much, specialty guitars. Teaching us to fish :)

Now here's one that really cooks my noodle...

Somewhere or another during a Google-frenzy I found an analysis that said my 12AT7 tube (which has a much lower plate resistance than most others in the 12AX7/5751 family) will have a gain closer to the 12AX7 than it would appear from just the oft-quoted 100 vs. 70 figure. And that furthermore, having like half the plate resistance will affect the operation of the tone stack.

Thanks so much, specialty guitars. Teaching us to fish :)

You're welcome. ;-)

Brent, that is correct. And that impedance difference is part of the problem when you pop a 12AT7 into this amp. Because the second stage is designed for half of a 12AX7. Besides that, the gain is just dropped way too low.

Remove the cathode bypass cap, use a nice 12AX7 and it's smooth sailing...

... Remove the cathode bypass cap, use a nice 12AX7 and it's smooth sailing...

+1 http://img.photobucket.com/albums/v82/rfdee/thumbsup.gif :mrgreen:

Hey Rob. For the man who has a wall of tricked out GA5s, I think I know your next step. You should outfit them with Tone Tubby 8" speakers! :grin:

Weber 8F150 works just as well if not better. :mrgreen:

Check out the bearded guy in the Roky Erickson video on this link.

Roky Erickson video link (http://admin.online.pbs.org/klru/austin/index.php?option=com_content&task=view&id=152&Itemid=637)

http://admin.online.pbs.org/klru/austin/flash/video/player2/index.php?xml=/klru/austin/images/stories/ACL/Episodes/2000s/2007/kol_roky/video/3312_roky_song.xml

Check out the bearded guy in the Roky Erickson video on this link.

Roky Erickson video (http://admin.online.pbs.org/klru/austin/index.php?option=com_content&task=view&id=152&Itemid=637)

That bearded dude can play but imagine the tone if he had taken the time to read this thread . . . .:lol:

That bearded dude can play but imagine the tone if he had taken the time to read this thread . . . .:lol:

Billy G isn't playing thru the GA-5. According to the link at the bottom of the Roky Erickson link, it list the gear he uses and says he plays thru a ''small Gibson combo'' and shows a pic of the GA-5.

Billy G isn't playing thru the GA-5. According to the link at the bottom of the Roky Erickson link, it list the gear he uses and says he plays thru a ''small Gibson combo'' and shows a pic of the GA-5.

Reading through the gear interview and blog responses someone said Mr. Gibbons plugged straight into a Crate V30, no pedals.

Billy G isn't playing thru the GA-5. According to the link at the bottom of the Roky Erickson link, it list the gear he uses and says he plays thru a ''small Gibson combo'' and shows a pic of the GA-5.

I see that now -

but looking at the video again I notice that when Billy G is just getting into his solo it looks to my eyes like his guitar cord is snaking right back to that GA-5 leading me inexorably to the conclusion that they are sharing the amp! It does have two inputs . . . .:lol:

...well, so much for that:

"We're sorry, this product has been discontinued."

-dh

I see that now -

but looking at the video again I notice that when Billy G is just getting into his solo it looks to my eyes like his guitar cord is snaking right back to that GA-5 leading me inexorably to the conclusion that they are sharing the amp! It does have two inputs . . . .:lol:
If Billy isn't actually playing through the GA-5 it certainly looks like he is playing through it. When you watch that video you don't recall the video as "the one where Billy plays through the Crate amp".

The video is a great piece of Gibson product placing.

There has been some talk about filter caps and tone in these amps and since I've rebuilt a handful of vintage GA-5s I thought I'd comment. As far as tone of various brands of filters I've used Sprague, Weber, Nichicon and Illinois. The only caps that have been noticeably inferior for me are the little dark blue 8uf Spragues like Gibson used in some of these GA-5 reissues. As a group those things sound really low-fi. The Weber caps sound fine and small and light enough to fit in any vintage amp plus the cost is so low. My favs are the Nichicons. The only defective cap I've ever had was a 16uf Sprague.

Vintage Gibson amps used 20-10-10 for the filters and IMO that is much preferable to the triple 8s or triple 16s in vintage Fenders. The preamp isn't over filtered which makes for a livelier tone. Bumping the first filter to 30uf makes a HUGE difference. I always thought the 8" speaker was overloading with the amp cranked but it's actually inadequate filtering. I always use 30-10-10 in my builds/rebuilds.

The vintage Gibbies from around 1960 used .02 coupling caps. I think this is better than the typical .1 used in tweed Fenders. Lets all the guitar frequencies through without all the mud.

The Gibson blowout made me jump on ebay and score a vintage blonde Skylark. It showed up today and I may start a thread with a pic of the guts to compare to the reissue.

There has been some talk about filter caps and tone in these amps and since I've rebuilt a handful of vintage GA-5s I thought I'd comment. As far as tone of various brands of filters I've used Sprague, Weber, Nichicon and Illinois. The only caps that have been noticeably inferior for me are the little dark blue 8uf Spragues like Gibson used in some of these GA-5 reissues. As a group those things sound really low-fi. The Weber caps sound fine and small and light enough to fit in any vintage amp plus the cost is so low. My favs are the Nichicons. The only defective cap I've ever had was a 16uf Sprague.

Vintage Gibson amps used 20-10-10 for the filters and IMO that is much preferable to the triple 8s or triple 16s in vintage Fenders. The preamp isn't over filtered which makes for a livelier tone. Bumping the first filter to 30uf makes a HUGE difference. I always thought the 8" speaker was overloading with the amp cranked but it's actually inadequate filtering. I always use 30-10-10 in my builds/rebuilds.

The vintage Gibbies from around 1960 used .02 coupling caps. I think this is better than the typical .1 used in tweed Fenders. Lets all the guitar frequencies through without all the mud.

The Gibson blowout made me jump on ebay and score a vintage blonde Skylark. It showed up today and I may start a thread with a pic of the guts to compare to the reissue.

Thanks for posting this info TNO. Have you had any experience with these Xicon e caps? and F&Ts? I've read mixed things about the F&Ts but have had no problems with them myself.

I may have to pop a 30uF in my Ri and see what I think.

Vintage Gibson amps used 20-10-10 for the filters and IMO that is much preferable to the triple 8s or triple 16s in vintage Fenders. The preamp isn't over filtered which makes for a livelier tone. Bumping the first filter to 30uf makes a HUGE difference. I always thought the 8" speaker was overloading with the amp cranked but it's actually inadequate filtering. I always use 30-10-10 in my builds/rebuilds.


This is what I suspected and is one of the things that I'm mosdt interested in trying in my GA-5. Replacing the first 16uF filter cap with a 30uF made a big difference in my 5E3 clone. It tightened it up quite a bit, enough that I wondered if three 22uF filter caps in the GA-5 were strangling it.

This is what I suspected and is one of the things that I'm mosdt interested in trying in my GA-5. Replacing the first 16uF filter cap with a 30uF made a big difference in my 5E3 clone. It tightened it up quite a bit, enough that I wondered if three 22uF filter caps in the GA-5 were strangling it.
Its very easy to try quickly. You can solder a cap (16uF or 22uF or 47uF or whatever) in parallel to each cap and try it out. I.e. just piggy back a 16uF onto the first 16uf, solder both ends and play it.

Another good thing to do is to add an additional filter stage, i.e. a 22uF or bigger with a small value resistor such as 150R to 240R before the existing first power cap. A cable tie will be OK to strap it to the first cap.

Its very easy to try quickly. You can solder a cap (16uF or 22uF or 47uF or whatever) in parallel to each cap and try it out. I.e. just piggy back a 16uF onto the first 16uf, solder both ends and play it.

The first filter cap in my 5E3 clone was two 16uF caps in parallel until I decided to replace them with a 30uF to neaten things up.

Love this thread!! I have a 1965 GA-5. One of the sweetest amps I own, Big or small! This was the only year (maybe 66 also) that they used 2 6BQ5/EL84s and one 12AU7 as the preamp. I constantly switch the AU7 for a AV7 when I want a little more dirt. One of my best recoarding amps! Not really good for play out, but one of the best recording amps aroundIMHO.

Cheers
ED

Jaybird: try reversing the OT leads-I've had the squealing problem on a new build and that fixed it.

The leads were not the problem. After testing your theory and thinking about it, I can say that the OT was properly wired. If not the amp would not have worked . In the past I have wired OTs backward by mistake and the squeal began immediatly. In the present problem, the squeal does not occur until the 47k NFB resistor is connected. It has been informative doing the various mods in this thread, but they don't all work for my amp. I removed the 22pf bypass, ,installed a 4.5M resistor on the input, kept the .1 coupling cap on the first preamp stage, and installed an 8 ohm output jack. The amp sounds great. Thanks for all of the help and good suggestions. This is one of the better threads in quite a while!

Welp, I did one of the trio of mods! And I did not hurt myself, or the amp! I really do appreciate all the advice for us fledgling techs.

So, I lifted the 25uf cap.

I like it waaaay more than adding the putting a 12AT7 in there, that just killed it IMO. The amp is just as loud, which is important to me, but the gain is much more tame and useable farther up the dial. A little bit more headroom too. Before the mod, when I dimed the volume on my amp and the guitar, it was waaaay over the top distortion, nothing I'd ever access. Now, that same spot is still over the top for me, but not nearly as much, and doesn't take up as much real estate on the dial. Really only the last bit of the sweep.

Yahoo! I did one, now I'll see if I'll try the others?? The volume is important to me, as I am gigging this little bugger and need as much as I can get. So I may not do the other two, as it sounds like those tame things down quite a bit. The first mod leaves things just as punchy and dynamic and tweedy, but the over the top distortion is not so much!


I'm proud that I was able to do it myself, and enjoy the changes I made :) Thanks to you fine folks!

droo

Just ordered one from music123.com yesterday for $299. It said they were not in stock and that they would email me when they were. Well, I got the email that mine shipped this afternoon and will be here on Tuesday. Nice! I can't wait. I sold a Pro Jr recently and now this will be my grab-n-go/practice amp.

In the past I have wired OTs backward by mistake and the squeal began immediatly. In the present problem, the squeal does not occur until the 47k NFB resistor is connected.
The squeal in the past is probably because there was already NF in the circuit...if there is no NF, then it doesn't matter what the phase of the OT is (in terms of NF induced squeal, at least). Your symptoms still look like an positive feedback issue...until you actually try it and prove it false, I'm not convinced...

Droo - I lifted the 25uf cap yesterday and completely agree with your assessment. The gain is more tame and doesn't go over the top until near the end of the dial. To my ears, it's not a radical change, just a nice, subtle improvement.

I've been experiment with gigging the GA-5 unmiked (I love simple). Last week I did a bar gig with about 60-80 people in it, and while it did great, it was too much gain for some songs. Yesterday, right after the mod, I played a private party for about 200 people in a single large room. We played our usual mix of old rock/r&b/blues songs, and this time (despite having to turn up louder because of the size of the room) I had fewer tunes where I was too gainy.

So Rob and Specialtyguitars - thanks for posting the mods, the photos, and the instructions for us noobs!

Ron Caselli

Just a shout out to any GA-5 owner who decides the little bugger isn't their "cup of tea", please shoot me a PM/email... I've been overcome by GAS & am looking to buy... but not for the $400-$700 prices of the one left over on the net! I got to this party WAAAAY late unfortunately...

Muchas Gracis!

Just a shout out to any GA-5 owner who decides the little bugger isn't their "cup of tea", please shoot me a PM/email... I've been overcome by GAS & am looking to buy... but not for the $400-$700 prices of the one left over on the net! I got to this party WAAAAY late unfortunately...

Muchas Gracis!


Looks like music123 has them in stock, I'd call instead of email :wink:

androo,

Have you called them to check? Because the web site lists it as "E-mail me when it's in stock" and "Special Order". Sounds like they will be getting some Real Soon Now (tm) like MF. For all I know they're just another MF alias anyway...

Ruger -

Did you see today's post that music123 just got some of these? This may be one of those rare times when you/we get a second chance at a great limited offer-

http://www.music123.com/Gibson-Goldtone-Les-Paul-Jr--Amp-481209-i1145531.Music123

androo,
Sounds like they will be getting some Real Soon Now (tm) like MF.

If 123 is just an alias for MF, there may not be any more...

I talked to MF a few days ago and they (Melinda) said their computer shows ONE coming in May and it is spoken for. To me, one coming by itself sounds like a computer error. Anyway, there may be no more amps after all.

DO TAKE THE OTHERS' ADVISE AND CALL though. I did on Wednesday and somehow scored a blem at a reduced price. They gave me a shipping confirmation number, so I think I really do have one coming. Yeah!

I'm proud that I was able to do it myself, and enjoy the changes I made :) Thanks to you fine folks!

droo

Congrats! You've just joined a fun and rewarding hobby!

It's all guesswork, absent any inside information, but it sure sounds like those $299 closeout amps were all built back in 2006 or early 2007. If so, Occam's Razor suggests that the simplest explanation is the most likely to be true and I'd say they were sitting on a shelf somewhere not selling at $700 so they just moved them all at $300.

It's entirely plausible that Gibson took a bit of a flyer having some amps built with premium components and (by all indications) USA labor and found that while people say they value those features they don't value them enough to actually buy the darned things at the resulting price point. The fact that a $700 amp flies off the shelf at $300 doesn't exactly obligate them to crank back up the production line.

I'll predict that some day soon Gibson will "reissue the reissue" and try to sell some Asian-made generic amps under the same model name for, say, $400 or so.

Well, I did it - pretty much blew out the Sig 8 speaker with the modded GA-5. Couldn't take the low end at 1/2 to 3/4 volume and now it farts out like crazy. Thankfully, the 8F150 is due in this Tuesday.

This just confirms (for me, at least) that the GA-5 circuit is specifically tweaked to push out lotsa treble and very little bass (hence, all that raunchy "tweed tone") 'cause any decent low end (like what the trinity mods offer) would cripple the Sig 8 speaker and make for unhappy customers.

Follow the Music123 link and check out the blem they have in stock - $594.96. Or you can tell them to e-mail you when they have a non-blem in stock - the price for the non-blem is $299. :mrgreen:

Must be a typo - the blem must be a special run relic :lol: :lol: :lol:

Well, I did it - pretty much blew out the Sig 8 speaker with the modded GA-5. Couldn't take the low end at 1/2 to 3/4 volume and now it farts out like crazy. Thankfully, the 8F150 is due in this Tuesday.

This just confirms (for me, at least) that the GA-5 circuit is specifically tweaked to push out lotsa treble and very little bass (hence, all that raunchy "tweed tone") 'cause any decent low end (like what the trinity mods offer) would cripple the Sig 8 speaker and make for unhappy customers.

This thread really drives home the point that everyone hears things differently... to some, including myself, this amp is a little on the "dark" side of the sound spectrum - to others too bright.

This thread really drives home the point that everyone hears things differently... to some, including myself, this amp is a little on the "dark" side of the sound spectrum - to others too bright.


My GA-5 my darkest amp.
My 5E3 clone, Mesa/Boogie Express 5:50, '66 Vibrolux Reverb and '68 Princeton Reverb are all capable of sounding much brighter.

To me , my GA-5 is bright compared to my 5F1. The Ga-5 has got some juice though!! Could be the difference between EL84 and 6V6 in similar circuits.

MF has a returned one at this point for about $ 509.00 if I understand right.

Shall we have a pool on whether anyone actually buys it at that price?

Well, I did it - pretty much blew out the Sig 8 speaker with the modded GA-5. Couldn't take the low end at 1/2 to 3/4 volume and now it farts out like crazy. Thankfully, the 8F150 is due in this Tuesday.

This just confirms (for me, at least) that the GA-5 circuit is specifically tweaked to push out lotsa treble and very little bass (hence, all that raunchy "tweed tone") 'cause any decent low end (like what the trinity mods offer) would cripple the Sig 8 speaker and make for unhappy customers.

To me this means you are using the heck out of your new amp. Thanks for torture testing the amp for us Rob; hope you had a blast knocking the cone out of that little 8" speaker!

This thread really drives home the point that everyone hears things differently... to some, including myself, this amp is a little on the "dark" side of the sound spectrum - to others too bright.
Yep, mine would be the complete opposite of bright. As though someone has thrown a quilt over it...or two. The factory speaker contributes to this some because I tried my 8" Vox Pathfinder speaker in it and it sounded better, or somewhat brighter, anyway.
MF has a returned one at this point for about $ 509.00 if I understand right.
Shall we have a pool on whether anyone actually buys it at that price?
It's gone. The only Gibson amp MF lists now is the GA20RVT. No scratch & dents of any kind at this time either.

Search results for "GA5" & "GA-5" return a Taylor acoustic. Before the Gibson would pop up too, even when it was out-of-stock.

It's gone. The only Gibson amp MF lists now is the GA20RVT. No scratch & dents of any kind at this time either.

Search results for "GA5" & "GA-5" return a Taylor acoustic. Before the Gibson would pop up too, even when it was out-of-stock.

I'm still waiting for a reply from Gibson re whether the GA-5 has been discontinued, but in a thread I started a while ago on the Gibson Forums, there is a reply today from someone who is claiming that he has word from Gibson Customer Service that the GA-5 production has ended. I've asked this posted to clarify, and if I get a response I'll post here.

I'm still waiting for a reply from Gibson re whether the GA-5 has been discontinued, but in a thread I started a while ago on the Gibson Forums, there is a reply today from someone who is claiming that he has word from Gibson Customer Service that the GA-5 production has ended. I've asked this posted to clarify, and if I get a response I'll post here.

When I asked where GA-5s were made the person from Gibson spoke about them in the past tense leading me to believe that they are no longer made.

No question that production has officially stopped on the GA-5, probably mid 2007. I dunno if anyone got a 2007 GA-5 and my guess is that there's a bunch more left to get blown out by MF & Co.

i hope some one else gets these. I hipped my friend to it and he scored one and loves it. I was set to pounce and went away to Maine for a week (where innerwebs are sketchy) and promptly forgot. BY time i went to score one they were gone. :(

I just snagged a like-new one for $299 from someone over at the gear page (missed the original blowout), and very glad I did. I mostly just play at home, so whether its gigable isnt an issue.

I love it. Reminds me of a DrZ 5 watter I had, but a little sweeter sounding. I am a big fan of boxy tweed sounds. Nice clean at bedroom volumes, but also takes pedals very well if you dont want to wake the family. Strat through a sunface was very nice. As was my Les Paul through an OCD. I also have a Marshall 1974x, which is my overall favorite. But the GA-5 holds it own (at one 5th the price) and the solid state rectification is nice on this for a different el-84 feel. Its a keeper.

Thanks for all the great info in this thread.

On my GA5, the EL84 is anchored with a spring type retainer, while the 12AX7 is anchored with more of a tube shield type retainer. Is this normal? (sounds like just a few of you have opened her up and thus know what lies beneath..........)

Reason I am pondering this is my 12AX7 is real snug, wheras the EL84 is extremely loose. I am getting quite a bit of lower end rattle, so I am wondering if this could be the source and if the EL84 maybe needs a more substantial retainer. (and logic tells me a spring (and thus the tube) will vibrate.....it just seems counter intuitive to put such a thing an amp, but then, what do I know????....I do see spring retainters sold on line.... !!) Anyway, could this be a source of rattle?

My other rattle theory is that the JJ EL84 has small pins....I know JJ had a run of small pin tubes, and I think it was the EL84's. Will a loose tube create a "rattly tone"?

Hoping to get rid of the rattle as it sounds and feels great! Thx!!

On my GA5, the EL84 is anchored with a spring type retainer, while the 12AX7 is anchored with more of a tube shield type retainer. Is this normal? (sounds like just a few of you have opened her up and thus know what lies beneath..........)

Reason I am pondering this is my 12AX7 is real snug, wheras the EL84 is extremely loose. I am getting quite a bit of lower end rattle, so I am wondering if this could be the source and if the EL84 maybe needs a more substantial retainer. (and logic tells me a spring (and thus the tube) will vibrate.....it just seems counter intuitive to put such a thing an amp, but then, what do I know????....I do see spring retainters sold on line.... !!) Anyway, could this be a source of rattle?

My other rattle theory is that the JJ EL84 has small pins....I know JJ had a run of small pin tubes, and I think it was the EL84's. Will a loose tube create a "rattly tone"?

Hoping to get rid of the rattle as it sounds and feels great! Thx!!


I've had a bunch of EL84 amps and it's definitely the EL84 tube itself that's prone to rattling, even with a tube spring retainer. You might wanna try a tube damper - http://herbiesaudiolab.home.att.net/

arrgh..I was afraid some one would say tube dampers...I have tried Herbie's tube dampers and they did nothing on some rattly 6L6's....

Is it the EL84 "innards" that tend to rattle or the fact that EL84's are typically held in place with some kind of medieval torture device looking thing with rattly springs on it??

arrgh..I was afraid some one would say tube dampers...I have tried Herbie's tube dampers and they did nothing on some rattly 6L6's....

Is it the EL84 innards that tend to rattle or the fact that EL84's are typically held in place with some kind of medieval torture device looking thing with rattly springs on it??

IMO, it's the EL84 design/build itself that's prone to rattling.

Sounds like swapping EL84's might do the trick....I do have couple of spares....JJ's unfortunatley....

Just not sure how to get that spring thingy off and THEN back on when tube swapping...

Sounds like swapping EL84's might do the trick....I do have couple of spares....JJ's unfortunatley....

Just not sure how to get that spring thingy off and THEN back on when tube swapping...


"JJ's unfortunately"? Huh? IMHO, JJ makes one of the better, if not best, EL84/6BQ5 tubes.

Yer kidding - removing the spring tube retainer is a problem for ya?

nope.....Not kidding.....

Lessee.....I'll guess....Remove at the amp "chassis"??....remove where the springs attach to the tube "grips" ?? just pull the friggin' thing down until I can get the tube out, hold in position, quickly insert new tube and reposition retainer and pray??? dunno.....

Never done it....I am sure it is VERY easy once you have successfully done it once or a few times and then maybe even do it on a regular basis

I am from 6L6 / 6V6 world, so please be gentle, as I am new to EL84 world

(and I just want to play!!! not screw with tubes !!!!!!!!!!! Argghhh!!!!.....nothing like just picking up my acoustic guitar and playing wiithout all the extra BS!!! )

nope.....Not kidding.....

Lessee.....I'll guess....Remove at the amp "chassis"??....remove where the springs attach to the tube "grips" ?? just pull the friggin' thing down until I can get the tube out, hold in position, quickly insert new tube and reposition retainer and pray??? dunno.....

Never done it....I am sure it is VERY easy once you have successfully done it once or a few times and then maybe even do it on a regular basis

I am from 6L6 / 6V6 world, so please be gentle, as I am new to EL84 world

(and I just want to play!!! not screw with tubes !!!!!!!!!!! Argghhh!!!!.....nothing like just picking up my acoustic guitar and playing wiithout all the extra BS!!! )

No need to remove the chassis to replace the power tube.

Set the amp upside down on a table somewhere with good lighting. This way you can see what's happening. Pull up on the spring retainer, and allow it to retract off to the side of the tube. Remove the tube gently pulling up while gently working it in a circular motion.

Notice the keying in the socket, so you can tell how to reinsert the old tube, or insert a new one, in the correct orientation. Gently install the tube, taking care not to bend the pins. When installed, pull up on the spring retainer, and carefully place it on the top of the tube, being careful of the tube's delicate tip.

Thanks so much for the help!!!!...So you do not actually remove the retainer, you just get it away from the tube to be removed.....

Without your guidance, I would have probably started taking the actual retainer apart and screwed the whole thing up......Guess the proper way to do this should have been very obvious to me though, so I apologize to all on this forum for being so stupid about this

With that said, next stupid question is...... if I replace a JJEL84 with another JJEL84, no need to do any kind of bias check or any such thang...true??

Thanks so much for the help!!!!...So you do not actually remove the retainer, you just get it away from the tube to be removed.....

Without your guidance, I would have probably started taking the actual retainer apart and screwed the whole thing up......Guess the proper way to do this should have been very obvious to me though, so I apologize to all on this forum for being so stupid about this

With that said, next stupid question is...... if I replace a JJEL84 with another JJEL84, no need to do any kind of bias check or any such thang...true??

No need to remove it from the chassis. That's why they use springs.

It should be fine bias wise. You could get a volt meter and a calculator to verify that the bias is correct, but you'd probably better leave that up to a tech.

yeh.....if I'm skairt of even dealing with a spring tube retainer, no need to even think about me checking the bias

I'm gonna try another JJ I have and may get an EH at my local music store to see if I can make bad rattle noise go bye bye with some tube rolling...

thanks again for all the advice

I just looked at the hit count for this thread, and it is almost 15,000.

Can you believe this many Tele players are keen on learning about and sharing info on this little small-run Gibson amp? Quite a surprise to me!

Mine is due in tomorrow's mail, right when I leave town for a week. As soon as I get back, I look forward to trying some of these great tips.

To me this means you are using the heck out of your new amp. Thanks for torture testing the amp for us Rob; hope you had a blast knocking the cone out of that little 8" speaker!

Didn't take much to damage the Sig 8, but then again that speaker is a mini mouse compared to a quality 8" driver. I should have the 8F150 arrive and installed tomorrow - that should be the ticket to handle the horsepower this li'l amp dishes out (with the mods, of course).

I just looked at the hit count for this thread, and it is almost 15,000.




It is not just about this one amp; it is about an excellent environment for those of us (like me) that have been around these things but never learned what was really going on inside, and have discovered some we'd like to know more.

If you can't get your hands on this amp, What would be a good second choice??? Thanks

If you can't get your hands on this amp, What would be a good second choice??? Thanks

The GA-5 was (or maybe still is) a fantastic value for the dollar - I dunno of any stock amp coming close.

If you can't get your hands on this amp, What would be a good second choice??? Thanks



I checked with Music123 and they still have - or maybe as I write this HAD? - the GA-5 NIB for 299.99 shipped in the USA.

i hope my uncle rob gets me one! got my fingers crossed! why can't i by it myself? cause i'm broke!

Gigged again last night with the GA5....very impressed. Hung in there no problem, it was a medium sized St. Paddy's Day restaurant gig, around 200 people or so. I mic'ed it through the PA, worked great. Put a SM57 on it.

As for stage volume, it was no problem hearing during solos, but funky rhythm parts were harder to hear as clearly as my Delta Blues, of course. I solved this problem by raising it up high on the amp stand, got it about waist level. After that, I could hear it all, and the band commented on how nice it worked!

For those of you who think this little bugger won't be appropriate for a gig, I'd try it out. I probably won't be using it at festivals this summer, as it obviously won't fill a large stage with sound....but for casuals and clubs where it's a tight stage, boy this thing just smokes! Put a mic on it, and all is well :)

I hope ya'll are enjoying yours too :)
droo

The Weber 8F150 just arrived and I pulled the farty Sig 8 and dropped in the big boy. As you can see by the images, the chassis fully clears the 8F ... the EL84 spring retainer ever so slightly touches the big ring magnet, but that could easily be tweaked/bent out of the way (or just removed). Of course, I'll build a totally new baffle board and cane grille it. :cool:

http://img.photobucket.com/albums/v82/rfdee/8f2.jpg

http://img.photobucket.com/albums/v82/rfdee/8f1.jpg

http://img.photobucket.com/albums/v82/rfdee/8f3.jpg

music 123 shows them on their website & will let you order them -- but it shows up in the cart as a special order / not in stock item . . .

Wouldn't surprise me to hear that a pile of 'em turned up somewhere, most likely at MF (music 123 is just MF in a wig). I bet you'll hear it here first, though not til Rob D has ordered #3, #4, #5 and #6. Keep your eyes peeled. Pretty likable little amp, better as time goes on & the speaker breaks in.

music 123 shows them on their website & will let you order them -- but it shows up in the cart as a special order / not in stock item . . .

Wouldn't surprise me to hear that a pile of 'em turned up somewhere, most likely at MF (music 123 is just MF in a wig). I bet you'll hear it here first, though not til Rob D has ordered #3, #4, #5 and #6. Keep your eyes peeled. Pretty likable little amp, better as time goes on & the speaker breaks in.

I want, no - I NEED - just two more. :cool:

They are one Music 123 for $299 right now.

The Weber 8F150 just arrived and I pulled the farty Sig 8 and dropped in the big boy. As you can see by the images, the chassis fully clears the 8F ... the EL84 spring retainer ever so slightly touches the big ring magnet, but that could easily be tweaked/bent out of the way (or just removed). Of course, I'll build a totally new baffle board and cane grille it. :cool:

http://img.photobucket.com/albums/v82/rfdee/8f2.jpg

http://img.photobucket.com/albums/v82/rfdee/8f1.jpg

http://img.photobucket.com/albums/v82/rfdee/8f3.jpg

Rob, just move the speaker down some on your new baffle and it'll be right on. Matter of fact, I think the things would easily hold 10" speakers if the speaker were mounted lower on the baffle.

Rob, just move the speaker down some on your new baffle and it'll be right on. Matter of fact, I think the things would easily hold 10" speakers if the speaker were mounted lower on the baffle.

Yep, easy stuff - umm, I've made LOTS of cabs. :mrgreen:

As I described in an earlier post on this thread, it'll take some speaker and/or chassis tweaking to fit in a 10".

Anyhoo, the new baffle has been sprayed and is drying. I lowered the speaker hole by 1/4", right down to the lip edge of the TV front. The speaker screws are recessed thanx to a Forstner bit, then CYA'd 'em in. After the paint dries I'll staple on the cane grille and that's about it.

http://img.photobucket.com/albums/v82/rfdee/baf2.jpg

http://img.photobucket.com/albums/v82/rfdee/baf4.jpg

http://img.photobucket.com/albums/v82/rfdee/baf5.jpg

Yep, easy stuff - umm, I've made LOTS of cabs. :mrgreen:

I wasn't questioning your experience. :wink:

One thing where I keep going wrong, is looking from behind, I forget that it is not a narrow panel tweed cab, and that the speaker actually can't really be moved very much, as you mentioned.

I wasn't questioning your experience. :wink:

One thing where I keep going wrong, is looking from behind, I forget that it is not a narrow panel tweed cab, and that the speaker actually can't really be moved very much, as you mentioned.


The cab spex and design pretty much dictate sticking with 8". Even after tweaking to fit in a 10", nearly 2" of the speaker bottom will get covered by the TV front lower panel. I've got my share of 10", 12" and even 15" single ended amps, so I kinda like having a few 8" versions around. :wink:

They are one Music 123 for $299 right now.


I just gave it the ole college try. My order (back-order) would not process.

BTW, I think whether you call MF or Music 123, you get the same switchboard.

Total conjecture, but I think somebody high up at MF/123 decided it would be cool to pull these out of the supply chain, and use them as bait at some point in the future when other sales have flagged. Hey, if you can I can buy something and wait for the price to go up, why can't they? And so begins the urban myth of the 'missing 200'.

Is the GA5 fixed bias, self bias, cathode bias???

And do I need to "rebias" when installing a new EL84? (and if so, how?)

The Weber 8F150 just arrived and I pulled the farty Sig 8 and dropped in the big boy. As you can see by the images, the chassis fully clears the 8F ... the EL84 spring retainer ever so slightly touches the big ring magnet, but that could easily be tweaked/bent out of the way (or just removed). Of course, I'll build a totally new baffle board and cane grille it. :cool:

http://img.photobucket.com/albums/v82/rfdee/8f2.jpg

http://img.photobucket.com/albums/v82/rfdee/8f1.jpg

http://img.photobucket.com/albums/v82/rfdee/8f3.jpg

Lookin' forward to your review of the new speaker Rob.

Is the GA5 fixed bias, self bias, cathode bias???

And do I need to "rebias" when installing a new EL84? (and if so, how?)

Cathode "self biased" - plug 'n' play.

So i've been lurking around this thread and poking around and playing with my GA 5. A couple of questions have arisen:

1. i know it was mentioned somewhere but there is a resistor between the pin and the wire on one of my tubes that has kept me hesitant from doing the NFB mod. The wire runs under the board from the volume pot and comes up through a drilled hole and there's a resistor between it and the pin. What is this resistor doing, what purpose does it serve, and more importantly can i still do the NFB?

2. I clipped the 1st stage 25uf cap and i plan to add a switch to allow me to bring back the nasty should i want it.

3. I jumpered the 1m resistor and 22pf cap tone stack and indeed the tone was beefier but i would also like to put this on a switch. I was actually wondering if it would be possible to have this on a pot so i could adjust how hefty the tone gets. Even with my tele its a bit too thick for my taste, at least with the stock speaker so a pot would be an ideal situation, if i could fit it. if not, then a switch would do just fine.

4. I have not added a standby switch, but I was wondering if it's necessary to purchase the switch that rob used or whether I could just use a normal on/off/on toggle.

5. Also, the grounding on the volume pot. I understand what I need to clip, but where would i run the wire to?

6. Thanks again for the amazing help this thread has been not only in tipping me off to this lovely amp but in giving me a guide to opening it up and messing with it.

Baffled?!

Stapled, cut, drying drum tight ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf1.jpg

Nice fit ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf2.jpg

8F150 locked 'n' loaded ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf3.jpg

Lotsa air vents ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf4.jpg

Plenty of room to co-exist with the chassis ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf5.jpg

EL84 retainer clears the mag ring ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf6.jpg

Warming up ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf7.jpg

Ah, mo' bettah!
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf8.jpg

Plenty of room to co-exist with the chassis ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf5.jpg

EL84 retainer clears the mag ring ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf6.jpg

Warming up ...
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf7.jpg

Ah, mo' bettah!
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf8.jpg

That looks great! Let us know how the speaker sounds after you break it in.

Hey Rob. I might have missed it since this thread is crazy long now, but how do you like the new speaker?

just let me get 1 @ $ 299

Ah, mo' bettah!
http://img.photobucket.com/albums/v82/rfdee/ga-5/baf8.jpg


Wow Rob, that looks better than what Gibson did at the factory.

BTW, did anyone ever determine if the metal baffle really blocked any sound? If so, was it really noticeable?

Rob, that caning looks great; I just know my granddad would have approved.

Well, maybe not of the music, but definitely the cane.

So i've been lurking around this thread and poking around and playing with my GA 5. A couple of questions have arisen:

1. i know it was mentioned somewhere but there is a resistor between the pin and the wire on one of my tubes that has kept me hesitant from doing the NFB mod. The wire runs under the board from the volume pot and comes up through a drilled hole and there's a resistor between it and the pin. What is this resistor doing, what purpose does it serve, and more importantly can i still do the NFB?


I dunno about that resistor and wire, but you can sure do the NFB no matter what.


2. I clipped the 1st stage 25uf cap and i plan to add a switch to allow me to bring back the nasty should i want it.

3. I jumpered the 1m resistor and 22pf cap tone stack and indeed the tone was beefier but i would also like to put this on a switch. I was actually wondering if it would be possible to have this on a pot so i could adjust how hefty the tone gets. Even with my tele its a bit too thick for my taste, at least with the stock speaker so a pot would be an ideal situation, if i could fit it. if not, then a switch would do just fine.


On a pot? Why? Use a switch to take the resistor/cap in an out. All three of the trio mods can be switched - in fact, if you use a DPDT switch, each of the mods could be completely removed from the circuit when in the off mode.


4. I have not added a standby switch, but I was wondering if it's necessary to purchase the switch that rob used or whether I could just use a normal on/off/on toggle.


You don't need the Carling, you can use an on/off/on toggle, but truthfully the Carling is SO much better and logical.


5. Also, the grounding on the volume pot. I understand what I need to clip, but where would i run the wire to?

The ground buss.


6. Thanks again for the amazing help this thread has been not only in tipping me off to this lovely amp but in giving me a guide to opening it up and messing with it.

....

With the new, airy and open cane grilled baffle board, and the spanking new massive Weber 8F150, the sound is BOLD, loud and in yer face - the speaker is stiff and will take a quite awhile to break in (as with any tight tolerance Weber) but even as is it sure is a major improvement over the Sig 8.

Theyre £500 over here, thats $1,000

Aaagh!

My Music 123 order is backordered to 5/1. But Amazon shows them as being in-stock and ready to ship from Musician's Friend, which shows them as being discontinued. Annoying.

With the new, airy and open cane grilled baffle board, and the spanking new massive Weber 8F150, the sound is BOLD, loud and in yer face - the speaker is stiff and will take a quite awhile to break in (as with any tight tolerance Weber) but even as is it sure is a major improvement over the Sig 8.

Personally, I like the original look better. And I dont like things bold and in my face.
no offense, just my preference.

Personally, I like the original look better. And I dont like things bold and in my face.
no offense, just my preference.

I left the GA-5 cane grille natural, but cane can take any stain hue ya like, even black. It's more difficult to work with cane grilling, but it's SO much stronger and more durable than cloth. Anyhoo, to each their own, as it should be. :cool:

http://img.photobucket.com/albums/v82/rfdee/cabs/cane-stain.jpg

Rob, I think my preference would be with a darker stain for sure. I can see the advantages definitely..
Nice work.

I'd like the cane grill stained as well.

I like natural cane with a stained hardwood cab, ala Mesa/boogie, quite a bit, though.

Rob: Can you still get cleanish sounds at lower volumes with the new 8F150 speaker?
(sort of a level equivalent to a Champion 600 maxed, but with no farty low end and maybe a bit dirtier)

Ordered Gibson GA5 a couple days ago at Music 123. Got email tonight that says my order was cancelled because the manufacturer has discontinued product.Oh well, that's an extra $299 I can blow on something else.

I ordered mine from Music123 on the 13th of this month and got it yesterday. It's a really cool little amp. Mine has the inspection sheet dated Nov. 22, 2006. So they are obviously shipping old stock.

Rob: Can you still get cleanish sounds at lower volumes with the new 8F150 speaker?
(sort of a level equivalent to a Champion 600 maxed, but with no farty low end and maybe a bit dirtier)

Absolutely clean tones at around 9 on the dial when using single coils.

Be on the look out. The one that I sent back to MF arrived there yesterday morning, so there should be a blem showing up on there website in the next couple of days.

There is a pre- "rear-screen goofy hole with box" - GA-5 for 299 on the FDP in the classifieds - somebody looking for one better act real fast as they are all gone at every outlet.

And here's one of the blowout models for only 299 that ships worldwide . . . .

http://cgi.ebay.com/Gibson-Goldtone-Les-Paul-Jr-USA-Class-A-Tube-Amplifier_W0QQitemZ330221502144QQihZ014QQcategoryZ 33040QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


edited to say: You're too late - its gone that quick.

Some component swaps - Atom filter caps (20/16/16), Jupiter .022 coupling caps, shielded the signal wire from the vol pot to the preamp tube socket. The 8F150 is *dark* - I removed the NFB resistor, for now ... might just put that in a switch. The Jupiters need some time to form and the Weber is a long way off from being broken in ... still, all the changes make quite a positive difference in tone for my old ears. A few more swaps and mods yet to do and then it's time to play the heck outta this great little amp!

Many thanx to Paul @ Specialty Guitars for all the great mods and help he's provided to me, and others! http://img.photobucket.com/albums/v82/rfdee/thumbsup.gif

http://img.photobucket.com/albums/v82/rfdee/ga-5/atoms-jupiters.jpg

My Weber 8A125 speaker arrived today and, much to my surprise, it fits with the magnet cover in place. I won't be able to change tubes without pulling the chassis, but that's not a big deal to me.

I've also removed the rear mesh screen and "chord box" and done the "trinity" mods, but think that I may undo them at some point. Also, as I've previously mentioned, I'm running a NOS RCA 12AX7 and EL84 in this amp.

I find it difficult to describe the precise changes that the new speaker made, but I like them. I think the tone, especially when driven to power tube distortion, is "smoother" for want of a better term.

I also think that I lost some volume--not a big deal for me and it actually makes it more basement friendly when there are other people in the house. I don't know if it would be thin-walled apartment friendly or not, but it certainly isn't overly loud.

I think that the new speaker, along with the other mods, make this a more humbucker friendly amp. It still sounds good with sinle coils, too.

All in all this is a terrific amp and I'm really glad that I got one.

Sorry, no pictures as I was too lazy to get out the camera after installing the speaker; besides Rob's photos are much better than mine...

Cassady

If you've done the GA-5 trinity mods, I think that if you also upgrade to a more robust speaker you may wish to remove the NFB and restore some of that raunchy sparkle and zing. In fact, I think the NFB might be the only mod worthy of making switchable, as there are times when it's desirable to have a more mellowed and quieter tone, and times when it just gets in the way of rock 'n' roll. IMO. So far. Ask me again next week. :cool:

Sidney Vicious, Thanks for the tip! It is on the way via USPS.

Steve

Sidney Vicious, Thanks for the tip! It is on the way via USPS.

Steve



Glad I could help!

Which one? :grin:

I think I just got one of the MF returns, but I'm whistling, hoping not to jinx myself.

This one came up $ 509 as well, but the nice young lady got this one busted down to the sub $ 299 price. Thank you, Mr. Easter Bunny.

Oh, and thanks again, Sid, nice tip. You really started a wave on this little amp.
And thank you, Rob. And thank you, Paul. And thank you, Don. And many others, thanks.

They're back . . . .

http://www.musiciansfriend.com/product/Gibson-Goldtone-Les-Paul-Jr.-Amp?sku=481209X

I just tried to order one and it said "out of Stock"...

It was there one minute at $230 as a second. Sorry !

I think a few returns are just trickling in, and it takes 5 days or so for the returned amp to clear all the hurtles and become available. I'll bet Filthy McNasty's return amp will be available on Monday or Tuesday, just estimating. Based on what the young lady was saying, they had but one as we spoke. I get nervous thinking about how long I 'chatted her up' before we locked this purchase in, wheww. I was so sure I didn't need one, but after all the fantastic posts and info here, I knew in terms of education about amps, it'd be the best money I'd yet spent.

If I wasn't amped up I would snatch this one on the FDP:

http://www.fenderforum.com/classified.html?ad=23946

A pre-messed with for 299 plus shipping - sounds like a deal to me.

Many thanx to Paul @ Specialty Guitars for all the great mods and help he's provided to me, and others!

My pleasure!

Like Rob, I installed a pair of the yellow Jupiter .02uF coupling caps. I also installed one of Rob's 3 way switches that allows for a standby function. With that I went ahead and got a hold of a NOS RCA smoked glass EL84. Along with the things I did earlier (they can be found in this thread somewhere) the amp sounds beautiful!

It's too bad that amps like this aren't available in this price range all the time. I mean that price allows for you to spend a few bucks to modify it if you like, and still not hurt your wallet too badly.

On the mods. I have kept the "trinity mods", as Rob calls them, in place. But I want to point out a few things.

1. I installed a brighter speaker

2. Telecasters are my main guitars

3. I like a more vintage style tone.

If my main guitar was a Les Paul, I think the amp would be too thick sounding, and I might reverse the mod that eliminates the 22pF/1 meg high pass filter. If I kept the stock speaker, or installed a darker one, I might reverse that mod as well.

As Rob did by reversing the NFB mod, this does make the amp "zinggier".

I'm certain I would leave the cathode bypass cap on the first preamp stage removed no matter what, as that reduction in gain at that point seems to help in almost all situations, but for some who want more distortion at lower volumes, not doing that mod may be the way to go.

The bottom line is that if you feel safe and comfortable modifying this little amp, you should be able to dial in the tone that's just right for you and your guitar.

Keep in mind that Gibson seemed to think it best, and the most versatile the way they shipped it, and actually installed more parts to do so than if they had built it with those mods already done. So they must have thought it worthwhile to do what they did.

If I wasn't amped up I would snatch this one on the FDP:

http://www.fenderforum.com/classified.html?ad=23946

A pre-messed with for 299 plus shipping - sounds like a deal to me.

Looks intriguing, but I am persona non grata over there...:mrgreen:

I just received my Carling progressive off/on/on switch from West Labs and some caps.

I'll be receiving a new Weller soldering station this week (my old one died and my back up iron isn't getting the job done). I can't wait to tear back into this amp!

I think I'm also going to temporarily mount a panel on the back of the amp with switches on it (I'll just trap it between the chassis and cabinet) to switch the "trinity mods" on and off to see what I like and don't like and in what combination. I've been iffy on the NFB loop. I think it makes the amp a tad too polite.

I'm also going to try lower value filter caps (I have a bunch of decent 16uF@475v caps here), fancy coupling caps and an alnico speaker (the speaker will have to wait until I stumble upon more money).

Folks have been wondering how we can have such a long thread on this amp. I think it's the most fun that I've ever had on this forum!

For me, there are definitely some more mods, swaps and testing left to accomplish ...

- I have a brighter Weber 8A125T on order as I think the 8F150 is too robust/dark to deliver the goods for both twangy rock 'n' roll and jazz/blues

- changing the 16uf Atoms for 10uf Atoms (22uf/10uf/10uf)

- finally getting around to adding the foil shield to the inside cab top

- pulling the UK Cliff jacks for Switchcrafts

- adding another shielded signal lead off the vol pot (to where the high pass one was located)

- adding back the NFB via a forward placed DPDT switch (which will completely remove the resistor when turned off) using shielded wire for all leads.

Using single coil pup guitars only, from what I'm hearing in my modded GA-5 in comparison with my stock one, removing the 25uf bypass cap is a good permanent mod. For the most part, I like the high pass filter removed as well - but that might be a candidate for a switch. I truly think the NFB should be switchable as this yields two quite different amps and there's value to both kinda tones.

Hey Y'all,

I performed the trinity mods (thanks Specialty Guitars and Rob for the great info!), and I think they are a dramatic improvement IMHO. The day I got the amp, I played it for 15 minutes with various guitars and I thought it sounded harsh and boxy and then I had to go out of town for a week. I just got back and did the mods and the boxy-ness is gone and the gain is lowered and managable. It's a darker sounding amp though. Really only my telecaster on the bridge pickup is a usable sound (and a really cool one at that); humbuckers, TV Jones classics -- no good -- too muddy. My G&L S-500 MFD bridge pickup sounds pretty good, but certainly not as good as the tele.

I compared the amp's sound with the NFB resistor to the sound without it and that was dramatic: the NFB really tames the gain and mellows the amp, without it the amp was too harsh and had lots of graining gain.

All of this is without a hint of speaker break in. I wonder, how can I make the amp a little brighter, so the middle position on my tele and the TV Jones pickups will sound decent, but still keep the lower gain structure I currently have?

Thanks again, what a terrific thread this is!

cheers,
Carl

p.s. I removed the grill from the back and removed the cord cubby -- that had to be the most lame design thing I've seen in a long time.

... All of this is without a hint of speaker break in. I wonder, how can I make the amp a little brighter, so the middle position on my tele and the TV Jones pickups will sound decent, but still keep the lower gain structure I currently have? ...

As mentioned by Paul, try unjumpering the 22pf/1m highpass filter. If that works well for ya with hummers, that would be a good candidate for a switch for when ya wanna get down 'n' dirty with single coils.

The jury is still out on using this baby for harmonica.

I gigged it for about 5 songs Thursday night and I was so busy trying to keep the hacks I was playing with all on the same page that I couldnt concentrate on what it sounded like.

I just set it at about 11 oclock and waded on in!

The mic I use behaves very similar to a guitar PU and I could hear differences in my sound according to my attack (or lack of).

If I let some air in around the mic and played soft and sweet, thats what I got.

When I sucked it down into my soul, it dirtied up pretty good!

My world famous train work on Folsum Prison Blues sounded a little thin and I cant decide whether I need some delay or reverb to widen things up.

Over all, its working out OK. I think I need to find my volume pedal and play with it a little.

Time will tell!

If I decide its not for me, you guys will be the first to know!:wink:

Hey Y'all,

I performed the trinity mods (thanks Specialty Guitars and Rob for the great info!), and I think they are a dramatic improvement IMHO. The day I got the amp, I played it for 15 minutes with various guitars and I thought it sounded harsh and boxy and then I had to go out of town for a week. I just got back and did the mods and the boxy-ness is gone and the gain is lowered and managable. It's a darker sounding amp though. Really only my telecaster on the bridge pickup is a usable sound (and a really cool one at that); humbuckers, TV Jones classics -- no good -- too muddy. My G&L S-500 MFD bridge pickup sounds pretty good, but certainly not as good as the tele.

I compared the amp's sound with the NFB resistor to the sound without it and that was dramatic: the NFB really tames the gain and mellows the amp, without it the amp was too harsh and had lots of graining gain.

All of this is without a hint of speaker break in. I wonder, how can I make the amp a little brighter, so the middle position on my tele and the TV Jones pickups will sound decent, but still keep the lower gain structure I currently have?

Thanks again, what a terrific thread this is!

cheers,
Carl

p.s. I removed the grill from the back and removed the cord cubby -- that had to be the most lame design thing I've seen in a long time.

If the amp is too dark. Another thing to consider, by itself, or in conjunction with using the 22pF/1 meg high pass filter, is reducing the value of the second coupling cap to .01uF or maybe lower. This will reduce some of the bass/lower mids.

Though pretty good for a flat cone speaker, replacing the stock one with a ribbed cone speaker will generally make the amp more articulate.

Yeah, I also removed that hideous cord box and the back grill.

As mentioned by Paul, try unjumpering the 22pf/1m highpass filter. If that works well for ya with hummers, that would be a good candidate for a switch for when ya wanna get down 'n' dirty with single coils.

A push/pull volume pot switch would be the trick for making that mod switchable.

Hello. This has been a very interesting thread to read. I own a GA-5, and have been tinkering with the different mods.

Does anybody know what a good cap value would be if I wanted a sound somewhere between stock and lifting the 25uf cap? How about for the high pass filter? What would a good resistor and cap value be to allow more bass in but not as much as when jumpered or removed?

Thanks.

Hey Y'all,

I performed the trinity mods (thanks Specialty Guitars and Rob for the great info!), and I think they are a dramatic improvement IMHO. The day I got the amp, I played it for 15 minutes with various guitars and I thought it sounded harsh and boxy and then I had to go out of town for a week. I just got back and did the mods and the boxy-ness is gone and the gain is lowered and managable. It's a darker sounding amp though. Really only my telecaster on the bridge pickup is a usable sound (and a really cool one at that); humbuckers, TV Jones classics -- no good -- too muddy. My G&L S-500 MFD bridge pickup sounds pretty good, but certainly not as good as the tele.

I compared the amp's sound with the NFB resistor to the sound without it and that was dramatic: the NFB really tames the gain and mellows the amp, without it the amp was too harsh and had lots of graining gain.

All of this is without a hint of speaker break in. I wonder, how can I make the amp a little brighter, so the middle position on my tele and the TV Jones pickups will sound decent, but still keep the lower gain structure I currently have?

Thanks again, what a terrific thread this is!

cheers,
Carl

p.s. I removed the grill from the back and removed the cord cubby -- that had to be the most lame design thing I've seen in a long time.

I posted my disappointment with this amp when I got it way back in the first couple of pages. I couldn't get a good sound out of past 9 0'clock on the volume. I really considered sending it back the next day, but I decided I had a month to try it out with the return policy. I played it everyday and it finally opened up about 10 days later. I'm pretty pleased with it now and I still think the speaker isn't totally broken in yet. I didn't mod mine yet becuase I wanted to wait and see how it sounded first. I'm not sure I want to mod it now but maybe a speaker swap.

Hello. This has been a very interesting thread to read. I own a GA-5, and have been tinkering with the different mods.

Does anybody know what a good cap value would be if I wanted a sound somewhere between stock and lifting the 25uf cap? How about for the high pass filter? What would a good resistor and cap value be to allow more bass in but not as much as when jumpered or removed?

Thanks.

I need to take off here, but really quickly...

1. reducing the value of the 1 meg resistor that is in parallel with the 22uF cap, will allow more bass/low mids. You could try a 500k and see what you think.

2. reducing the value, significantly, of that cathode bypass cap, will make the amp sound brighter, as the lower value reduces the gain of the bass, but not the treble. Fenders typically use 25uF, and Marshall lead channels often use .68uF to be brighter and "zingier".

I need to take off here, but really quickly...

1. reducing the value of the 1 meg resistor that is in parallel with the 22uF cap, will allow more bass/low mids. You could try a 500k and see what you think.

2. reducing the value, significantly, of that cathode bypass cap, will make the amp sound brighter, as the lower value reduces the gain of the bass, but not the treble. Fenders typically use 25uF, and Marshall lead channels often use .68uF to be brighter and "zingier".

Davenoid, you made me think of something that I should have before.

Probably a nicer sounding way, and definitely more orthodox way, to have this be brighter and zingier, and less muddy, would be to jumper that silly high pass filter, and instead, replace that 25uf preamp bypass cap with a .68uF or a 1.5uF.

.68uFs can be kind of large, but Mallory makes a 150 in .68 that is small.

Rob, you have 10 or 12 of these amps now right? You should try this on one with the stock speaker, and see what you think. I'm betting it would be really good, especially with humbuckers. But the only way to know is to try it.

... Rob, you have 10 or 12 of these amps now right?

Nah, only a measly five so far. :roll:

You should try this on one with the stock speaker, and see what you think. I'm betting it would be really good, especially with humbuckers. But the only way to know is to try it.

I agree - all the mods you've outlined are parameter value tweakable, and since all amps are unique to some degree, and what and how we feed them are even more variables, it's all just an "experiment of one" waiting to happen, should you have the desire, time, and maybe a few bucks.

The bypass lift alone solved most of my boxy/raspy issues, since all I really use are tasty single coils in Teles and Strats.

BTW, ya hooked me good - I got some of those Jupiters on order. :mrgreen: :cool:



....

It all works out in the end.

The $299 and the return policy was just too good not to give the GA-5 a try. What I realized was that I really like a super clean amp so that I can control the gain with my feet. My search for low powered tube amp continues but now I have a much better idea of what I am looking for. This eliminated quite a few choices that I had in mind.

Now having some extra cash in my pocket enter Brad at Tonefactor. He had posted on the TF forum that he was now taking orders on Paul Cochrane's Timmys. With such a long waiting period I figured that there was no way that I would be able to get one, but I got one of the last ones that Brad had and I should be receiving it sometime later in the week. It just kind of fell into my lap.



Boris, I am glad that it worked out for you as well.

The $299 and the return policy was just too good not to the GA-5 a try. What I realized was that I really like a super clean amp so that I can control the gain with my feet. My search for low powered tube amp continues but now I have a much better idea of what I am looking for. This eliminated quite a few choices that I had in mind.

That comment interests me and I'd like to followup briefly. So what will you be looking at next?

And what sorts of music do you play?

That comment interests me and I'd like to followup briefly. So what will you be looking at next?

And what sorts of music do you play?

First, I am a home player so a low power amp only makes sense. In the past I have owned both a Blues Jr. and a DRRI. I work nights and I try not to change my sleep habits too much on my days off, so the DRRI became extinct very quickly. It got turned on less than a hand full of times in the first year and a half after I went back to working nights and out the door it went. Very Good amp but it was just no longer suited my situation.

After trying out the GA-5 it eliminated any Tweed style amps. I was considering a 5F1 or 5e3 style clone but the breakup being what it is I believe that it would not be a good choice. I think that a Princeton Reverb (12-18 watts and 10" speaker) would be what I will try to look at next for the Fender clean sound and tube driven reverb. Finding a used silverface to demo is rather difficult around here and I am reluctant to buy one off of Ebay only to turn around and resell it if I do not like it. However, from what I understand Fender is going to reissue them so that could make things easier. Although going back to a Blues Jr. is not out of the question even with the SS reverb and EL tubes.

Anyway, Other than some Link Wray/Dwayne Eddie style stuff I play mostly rhythm guitar but I have picking up more lead lately. I have been picking through some Charlie Christian, T-Bone Walker, Grant Green, & Freddie King books for the past couple of months. I like so called alt-country and '60's British Invasion stuff as well.

I am just looking for some decent tone just like everyone else.

Don't mean to hijack, just answering a question.

ObGA5:

I've somehow lost the thread of negative feedback in this discussion and can't recall whether the stock GA-5 has it or not. My Champion 600 actually has a bunch of global NFB with a 2.2k resistor going back to bias the second preamp stage. I think that makes it more '64 Blackface than Tweed, circuit-wise. It is to my ears not a raw sounding amp at all (at least not once the fizzy Chinese 12AX7 was discarded).

From what little I know of tube electronics, I'd think the presence and amount of negative feedback might be the single most important indicator of whether an amp will have a tone you and I enjoy (and I think we have quite similar tastes in that regard) versus wild distortion and rawness. So my point being that "Tweed" in the name or on the cabinet may not be as simple an indicator as we tend to think.

A stock GA-5 has no NFB and is very tweedy toned. The trinity mods tame that to a Very Great degree.

First, I am a home player so a low power amp only makes sense. In the past I have owned both a Blues Jr. and a DRRI. I work nights and I try not to change my sleep habits too much on my days off, so the DRRI became extinct very quickly. It got turned on less than a hand full of times in the first year and a half after I went back to working nights and out the door it went. Very Good amp but it was just no longer suited my situation.

After trying out the GA-5 it eliminated any Tweed style amps. I was considering a 5F1 or 5e3 style clone but the breakup being what it is I believe that it would not be a good choice. I think that a Princeton Reverb (12-18 watts and 10" speaker) would be what I will try to look at next for the Fender clean sound and tube driven reverb. Finding a used silverface to demo is rather difficult around here and I am reluctant to buy one off of Ebay only to turn around and resell it if I do not like it. However, from what I understand Fender is going to reissue them so that could make things easier. Although going back to a Blues Jr. is not out of the question even with the SS reverb and EL tubes.

Anyway, Other than some Link Wray/Dwayne Eddie style stuff I play mostly rhythm guitar but I have picking up more lead lately. I have been picking through some Charlie Christian, T-Bone Walker, Grant Green, & Freddie King books for the past couple of months. I like so called alt-country and '60's British Invasion stuff as well.

I am just looking for some decent tone just like everyone else.

Don't mean to hijack, just answering a question.

Sounds like a silverface Princeton Reverb would be just the amp for you except maybe for one small thing. At 15 watts and with a 10" speaker, you may find that it is not much less loud than your DR.

I'd take a used silverface in a heartbeat over a future Ri.

Sounds like a silverface Princeton Reverb would be just the amp for you except maybe for one small thing. At 15 watts and with a 10" speaker, you may find that it is not much less loud than your DR.

I'd take a used silverface in a heartbeat over a future Ri.

That is what I was affraid of and keeps me from buying one without trying it out first.

That is what I was afraid of and keeps me from buying one without trying it out first.

That's a shame. I guess that's the one thing I have in abundance down here in this forsaken place. I can make as much racket as I like, with no-one right nearby to complain. I plan to run this thing through a lil cabinet that will take a nice quality 10 inch speaker. If the one I get is a good one, that is.

It has reverb but no tone control. I'd rather put my $300.00 bucks toward a vintage Fender tube, even if it costs more. The Fender already will have more features and will be a better investment. BUT, $300.00 ain't bad for this, especally if shipping is free...if you can find one.

I've been following this thread from the beginning, but still haven't made any of the mods. I have a few questions though.

1. Can the 8 ohm tap (mod) and 4 ohm tap be used simultaneously?
2. Can I used both inputs simultaneously without causing damage? i.e. Guitar and mic.
3. Can you run a 8 Ohm cabinet from the current 4 Ohm tap. I can see how lower impedance would be a problem, but other than having more resistance, what harm could using an 8 Ohm speaker cause?

I'm curious why many folks are doing these mods, but very few are changing out the speaker. Seems to me this is where one could modify the tone to their liking. Extra cost? Also, not much talk about 8" speakers other than a couple of Weber's that have been mentioned. Any other good 8's out there that you guys would recommend?

I've been following this thread from the beginning, but still haven't made any of the mods. I have a few questions though.

1. Can the 8 ohm tap (mod) and 4 ohm tap be used simultaneously?

NO

2. Can I used both inputs simultaneously without causing damage? i.e. Guitar and mic.

Sure

3. Can you run a 8 Ohm cabinet from the current 4 Ohm tap. I can see how lower impedance would be a problem, but other than having more resistance, what harm could using an 8 Ohm speaker cause?

Yes, but the tone/volume may suffer somewhat


I'm curious why many folks are doing these mods, but very few are changing out the speaker. Seems to me this is where one could modify the tone to their liking. Extra cost? Also, not much talk about 8" speakers other than a couple of Weber's that have been mentioned. Any other good 8's out there that you guys would recommend?

The circuit is VERY tweedy and some of us like to tame that harsh boxy tone down a few notches without changing out the speaker. That's where Paul (Specialty Guitars) suggested a number of treble taming mods that opened the amp up to different tones. There are lotsa good 8" speakers to play around with, it just takes time and money. More robust speakers will also darken and tame the tweed tone. YMMV.




....

I'm curious why many folks are doing these mods, but very few are changing out the speaker. Seems to me this is where one could modify the tone to their liking. Extra cost? Also, not much talk about 8" speakers other than a couple of Weber's that have been mentioned. Any other good 8's out there that you guys would recommend?

Good speakers are very expensive. The mods that we've been messing with are very in expensive, even free.
It's best to exhaust all of the inexpensive solutions first.

My amp will eventually have an alnico speaker in it. Probably a Weber 8A100T or 8A125T.

I lean towards Weber because of his selection of alnico speakers.

3. Can you run a 8 Ohm cabinet from the current 4 Ohm tap. I can see how lower impedance would be a problem, but other than having more resistance, what harm could using an 8 Ohm speaker cause?


Like a Fender Champ, the GA-5 sounds very thin and wimpy with an 8 ohm speaker. It won't harm the amp though.

Good speakers are very expensive. The mods that we've been messing with are very in expensive, even free.
It's best to exhaust all of the inexpensive solutions first.

My amp will eventually have an alnico speaker in it. Probably a Weber 8A100T or 8A125T.

I lean towards Weber because of his selection of alnico speakers.

I've got an 8A125T on order, it should be killer.

I've been following this thread from the beginning, but still haven't made any of the mods. I have a few questions though.

1. Can the 8 ohm tap (mod) and 4 ohm tap be used simultaneously?
2. Can I used both inputs simultaneously without causing damage? i.e. Guitar and mic.
3. Can you run a 8 Ohm cabinet from the current 4 Ohm tap. I can see how lower impedance would be a problem, but other than having more resistance, what harm could using an 8 Ohm speaker cause?

I'm curious why many folks are doing these mods, but very few are changing out the speaker. Seems to me this is where one could modify the tone to their liking. Extra cost? Also, not much talk about 8" speakers other than a couple of Weber's that have been mentioned. Any other good 8's out there that you guys would recommend?

I can't speak for everyone else, but changing the speaker is something I did early on (I went with a Kendrick 8") and mentioned doing so several times in this thread. I think Rob planned to change his early on, but had to wait for it to arrive.

But, the whole point was to show that this very affordable amp could be dialed in for almost anyone's tonal needs (within reason), for very little additional money. For some who can't afford to mess with speakers, some combination of those mods might be all that's needed to get the amp sounding the way they like. For those who can swap speakers and tubes, same thing. Some combination of those mods may be the ticket to make it that much more to their liking. Or, for some, leaving the amp box-stock may be exactly what they want.

The mods that we've been messing with are very inexpensive, even free.
It's best to exhaust all of the inexpensive solutions first.

Exactly. Of the "trinity mods" as Rob calls them, two of them are only removing or jumping components that are already installed in the amp. They cost nothing at all. And the third requires a 10 cent resistor that can be had from Radio Shack.

I thought this amp had reverb. Am I mistaken?

Hi folks. Here's a question for ROB DiSTEFANO, and/or anyone else using a Weber 8F150 in a GA-5. When you ordered it, how did you decide between the "paper dome with flat top" dustcap and the "H" (harp?) dustcap? How do they differ functionally & tonally?

I posed these questions to Ted Weber who simply said "If you are going to use a lot of distortion all the time, I'd use the H dustcap." I researched "H" caps on the web and found comments like "tames highs" and "reduces feedback", but that's about it.

ROB, WHICH DUSTCAP DID YOU CHOOSE & WHY?

I'm using a stock (non-mod'd) GA-5 reissue. I'm deliberately postponing any circuit mods until I hear the stock circuit with nicely broken-in Weber 8F150.

Those of you considering the 8F150 may find the following feedback from Ted Weber useful...

ME: I'm looking for an overall "larger" sound that doesn't sound so "boxy". A little more bottom end would be great!

TED: I'd go with the 8F150. Big low end, lots of punch and dynamics... as well as overall loudness.

ME: How do the 8A125 and 8F150 differ?

TED: 125 brighter, louder. 150 bigger, louder, more low end and punch.

I thought this amp had reverb. Am I mistaken?

You are major mistaken.

Hi folks. Here's a question for ROB DiSTEFANO, and/or anyone else using a Weber 8F150 in a GA-5. When you ordered it, how did you decide between the "paper dome with flat top" dustcap and the "H" (harp?) dustcap? How do they differ functionally & tonally?

I posed these questions to Ted Weber who simply said "If you are going to use a lot of distortion all the time, I'd use the H dustcap." I researched "H" caps on the web and found comments like "tames highs" and "reduces feedback", but that's about it.

ROB, WHICH DUSTCAP DID YOU CHOOSE & WHY?

I'm using a stock (non-mod'd) GA-5 reissue. I'm deliberately postponing any circuit mods until I hear the stock circuit with nicely broken-in Weber 8F150.

Those of you considering the 8F150 may find the following feedback from Ted Weber useful...

ME: I'm looking for an overall "larger" sound that doesn't sound so "boxy". A little more bottom end would be great!

TED: I'd go with the 8F150. Big low end, lots of punch and dynamics... as well as overall loudness.

ME: How do the 8A125 and 8F150 differ?

TED: 125 brighter, louder. 150 bigger, louder, more low end and punch.


Paper dome - only 'cause I know that works for me, dunno about the H cap.

IMO, the 8F150 is quite dark, loud as an 8" will ever get, Huge low end. I have an 8A125T (full ribbed cone) on order and I've used this speaker in lotsa Champs - great for rock 'n' roll and yet will mellow out fine for jazz and blues.

Rob, I think you should put togeter some sort of "mod. booklet". There is no way I could not go through all 17 pages to sort out the mods. (especially on dial up). That would super cool to see something handy like this. I would buy one.

Steve

Rob, I think you should put togeter some sort of "mod. booklet". There is no way I could not go through all 17 pages to sort out the mods. (especially on dial up). That would super cool to see something handy like this. I would buy one.

Steve

Page 7 of this thread pretty much covers everything.

http://www.tdpri.com/forum/amp-central-station/99134-%24299-gibson-tube-amp-made-usa-7.html#post1144412

Paper dome - only 'cause I know that works for me, dunno about the H cap.

IMO, the 8F150 is quite dark, loud as an 8" will ever get, Huge low end. I have an 8A125T (full ribbed cone) on order and I've used this speaker in lotsa Champs - great for rock 'n' roll and yet will mellow out fine for jazz and blues.

Thanks Rob. Based on your experience, how would you characterize the 8F150's ability to handle rock-n-roll, blues, & jazz? I'm hoping to use this speaker in a (currently) bone stock GA-5 to play a mix of 25% clean/jazz, 50% bluesey distortion, 25% classic rock distortion (ala ZZ-TOP).

I can't speak for everyone else, but changing the speaker is something I did early on (I went with a Kendrick 8") and mentioned doing so several times in this thread. I think Rob planned to change his early on, but had to wait for it to arrive.


I had an 8" Kendrick speaker that I threw as an extra speaker with a Champ I sold a couple of years ago:cry:

Thanks Rob. Based on your experience, how would you characterize the 8F150's ability to handle rock-n-roll, blues, & jazz? I'm hoping to use this speaker in a (currently) bone stock GA-5 to play a mix of 25% clean/jazz, 50% bluesey distortion, 25% classic rock distortion (ala ZZ-TOP).

The 8F150 will be a HUGE boost in tone over the stock Sig 8, and will add a huge low end rumble. You might wanna also consider the 8A125T or even the Chicago Vintage CVA8.

Now that the .022uf Jupiter coupling caps have pretty well formed after over 7 hours of playing, the tone just blooms out with more presence and warmth. Definitely another great mod. Heck, I'm gonna change all my amp's couplers to Jupiter's - thanx for the heads up on the Jupiters, Paul!

There's a neat YouTube video of a before (Orange Drops) and after (Jupiters) swap out ...

http://www.youtube.com/watch?v=njw06rLLDgs

GA-5 Mods and Upgrades (so far, I think - what'd I forget Paul?)

NOTE: after pulling yer GA-5 chassis and before sticking yer fingers inside it, drain the filter caps!!!

"trinity circuit mods" (total cost, about 25 cents)
1. lift/snip(and remove - optional) the 25uf cathode bypass cap
2. jumper (and remove - optional) the high pass 22pf cap/1m resistor coming off the vol pot
3. add a 47k NFB (negative feedback) resistor from the yellow wire on the RCA jack to pin 8 of the preamp tube socket

other circuit and functional mods
4. better, more robust 8" speaker with more low end and punch
5. remove the cab's cord cubby
6. remove the rear grille
7. remove the baffle's mesh grille under the cloth grille
8. add a standby switch (Carling progressive 3-way switch preferred)
9. shield the upper inside of the GA-5 cab (heavy duty alum foil works fine)
10. shield the signal lead off the vol pot to pin 7 of the preamp tube socket
11. break the ground buss between the preamp and power sections
12. rewire the vol pot ground
13. add an external speaker 8 ohm 1/4" jack, or replace the RCA jack with a 1/4" jack, and/or replace the yellow OT wire for the green OT wire and run with a new 8 ohm internal speaker
14. replace the yellow .022uf Mallory coupling caps with something better (Jupiters!)
15. change the filter cap values (stock is 22/22/22) to maybe 22/10/10 - a good thing to do if they aren't already Spragues, and replace with something better (Atoms, F&Ts, etc.)
16. change the UK Cliff jacks to better Switchcraft jacks

Trinity mods #1 and #2 (top image) - NFB mod #3 (bottom image)
http://img.photobucket.com/albums/v82/rfdee/ga-5/ga5a.jpg

Carling on/standby/off switch (top image) - external 8ohm speaker jack (bottom image)
http://img.photobucket.com/albums/v82/rfdee/ga-5/ga5b.jpg

Ground buss break (top image) - Atom filter caps, Jupiter coupling caps, shielded signal lead (bottom image)
http://img.photobucket.com/albums/v82/rfdee/ga-5/ga5c.jpg

Shielding the inside cab top with alum foil
http://img.photobucket.com/albums/v82/rfdee/ga-5/ga5d.jpg

So you have to do all those mods just to get that thing to sound good?

So you have to do all those mods just to get that thing to sound good?

Short answer - Absolutely Not.

More to the point answer - If you like the stock tweedy tone, then enjoy the GA-5 as is, as lotsa folks do. However, if yer mind's ear envisions a different more refined sonic flavor then that's what one or more of the tone tweaking mods offered might do for you. Lots also depends on what kinda music you'll play with this amp, and what kinda guitars you'll feed it. Some of the mods are purely functional and have little or nothing to do with tone, but address issues of design and usage.

So you have to do all those mods just to get that thing to sound good?

Yeah that's what I wanna know too!

Mine should be arriving this wed. my uncle rob d. hooked me up with one of his. He did some slight modifying for me already. I beleive he sheilded something in the preamp circuit, and put in a 3 way switch.

He said he wanted me to hear it the way it was first and that I could always mod it some more.

I got a real good amp guy close by to do it for me.

I guess if it wasn't worth having it stock, at least when I mod it, I will notice the difference!

uncle rob u still up? I thought ya b sleepin by now..wanna talk to ya u bout the gibson ga5

GA-5 Mods and Upgrades (so far, I think - what'd I forget Paul?)

Wow Rob, you remembered more than I did!

Now everyone who is interested in these amps and the mods: PLEASE BOOKMARK THIS PAGE SO YOU CAN FIND ROB'S LIST!

I've been following this thread from the beginning, but still haven't made any of the mods. I have a few questions though.

1. Can the 8 ohm tap (mod) and 4 ohm tap be used simultaneously?
2. Can I used both inputs simultaneously without causing damage? i.e. Guitar and mic.
3. Can you run a 8 Ohm cabinet from the current 4 Ohm tap. I can see how lower impedance would be a problem, but other than having more resistance, what harm could using an 8 Ohm speaker cause?

I'm curious why many folks are doing these mods, but very few are changing out the speaker. Seems to me this is where one could modify the tone to their liking. Extra cost? Also, not much talk about 8" speakers other than a couple of Weber's that have been mentioned. Any other good 8's out there that you guys would recommend?

Thanks to everyone who responded to my questions. I did the first mod tonight. Never believed a little snip of a wire could make such a profound difference. Harshness and over top high end is gone. Distortion is still a hard for my taste (when driven hard), but overall the sound of the amp is much better.

I wanted to try another power tube, but unfortunately the EL-84 boogie tube I have on hand wont fit. I'm curious why Gibson made such a small cut out around the tube that precludes the use of some tubes?

I've read that some had issues fitting the 12AX7, but I've been able to roll various tubes in here with not problem.

Carling off/standby/on added.

Rob, is there a part number on the Carling Super Heavy Duty DPTTP? We couldn't find it in the Mouser catalogue.

So you have to do all those mods just to get that thing to sound good?

From a post towards the top of this page...

But, the whole point was to show that this very affordable amp could be dialed in for almost anyone's tonal needs (within reason), for very little additional money. For some who can't afford to mess with speakers, some combination of those mods might be all that's needed to get the amp sounding the way they like. For those who can swap speakers and tubes, same thing. Some combination of those mods may be the ticket to make it that much more to their liking. Or, for some, leaving the amp box-stock may be exactly what they want.

Rob, is there a part number on the Carling Super Heavy Duty DPTTP? We couldn't find it in the Mouser catalogue.

Carling DPTTP Progressive ...

http://www.westlabs.com/Switches.HTML

Carling DPTTP Progressive ...

http://www.westlabs.com/Switches.HTML

Thanks, I had already seen the link,....I ordered two last night but I was looking for the Carling part #, I'll know soon enough, thanks again for your work, etc.

Stephen

Anyone tried an acoustic through this?

Rob- dropping those two filters to 10uF will give the amp just a little more life but bumping the first cap to around 30uF REALLY helps the amp to handle bass w/o farting out.

I'm going to trade a guitar for a un-opened box GA-5 today :)

Mine remains un-modded except for removal of the ridiculous heavy metal screens - front and back - and that goofy cord box.

Truth be told it is hard to say if the sound is noticeably different - but sure it makes me feel better.

Will try a vintage Jensen alnico I have - but otherwise I plan to leave the guts of the amp stock as I like it just the way it is.

My Musicians Friend GA-5 Blem just arrived. On careful inspection, I can not tell that it is not a new unopened amp. I feel so lucky not just to get one but to save some significant extra bucks as well!

Played it last night for a half an hour and just did the same again. While I look forward to doing some tinkering (all part of the fun), I can also confirm that the amp sounds just fine as-is. I am mightily impressed.

As I suspected, it is very cool with a Holy Grail or a little delay in front. Or, when you turn it up halfway, nothing else is needed. Thus far, all of my playing is with my Tele. Sounds good on all pickup selections. A fair amount of harmonic complexity for a small amp - very musical. More so than my VibroChamp I think. After a side-by-side test I will know more.

(BTW, I've seen two of these amps show up on my local Craig's List at decent prices. If you don;t have one and want one, keep your hunt going. Something will turn up.)

Mine remains un-modded except for removal of the ridiculous heavy metal screens - front and back - and that goofy cord box.

but otherwise I plan to leave the guts of the amp stock as I like it just the way it is.

Nothing wrong with that at all. Gibson must have thought the amp was the most versatile the way they sold it, and it rocks out of the box, so no need to feel that you "must" do any mods.

Those screens and that cord box are just too weird. I'm with you, they may not hurt anything, but I feel better with them removed!

Nothing wrong with that at all. Gibson must have thought the amp was the most versatile the way they sold it, and it rocks out of the box, so no need to feel that you "must" do any mods.

Those screens and that cord box are just too weird. I'm with you, they may not hurt anything, but I feel better with them removed!

Mine is on the way through Purolator. Should be here in a few days.
Why dont you guys like those screens? What about that cord box is weird?
Sorry , I haven't seen it yet other than pics.
I see the older ones didn't have them ,and that small circular cut-out in the corner...
Nothing wrong with extra safeguards, incase a curious kid/ animal wants in is there?

It's hard to say but,I think i'm going to leave mine as is.

Has anyone got any sound clips of these Amps yet? really interesting thread but it would be great to hear how it sounds before and after the mods.
Stax

Mine is on the way through Purolator. Should be here in a few days.
Why dont you guys like those screens? What about that cord box is weird?Sorry , I haven't seen it yet other than pics.
I see the older ones didn't have them ,and that small circular cut-out in the corner...
Nothing wrong with extra safeguards, incase a curious kid/ animal wants in is there?

It's hard to say but,I think i'm going to leave mine as is.



The cord box is too small to easily handle the power cord - which is very short to begin with - no doubt because of the small box.

With the box gone you can fit the cord in the back easily when not using the amp. And with the rear screen gone you can fish it back out again when you want to play.

The rear screen would serve protect a kid who really tried hard - from getting his fingers scortched by a hot tube. But I do believe there are no exposed electrical contacts in the rear so I think he is not subject to electrocution. The exposure to the chassis from the rear is comparable to that of a vintage Champ - a design I believe duplicated by mulitple amplifier companies today w/o safety issues.

I think in this case Gibson chose some extreme safety overkill.

As for the front grill - it is so heavy duty that it could stop a hurled cue stick. I have several vintage amps that have stood the test of time - but not a hurled cue stick! - for 40 years with nothing but a grill cloth to protect the speaker.

Why Gibson put its speaker behind such a heavy grill is anybody's guess.

Davenoid, you made me think of something that I should have before.

Probably a nicer sounding way, and definitely more orthodox way, to have this be brighter and zingier, and less muddy, would be to jumper that silly high pass filter, and instead, replace that 25uf preamp bypass cap with a .68uF or a 1.5uF.

.68uFs can be kind of large, but Mallory makes a 150 in .68 that is small.

Rob, you have 10 or 12 of these amps now right? You should try this on one with the stock speaker, and see what you think. I'm betting it would be really good, especially with humbuckers. But the only way to know is to try it.

Thanks for the tips! I'll check in again after I've tried some mods, and let everyone know what I think. And I'd just like to reiterate that this amp doesn't need mods to sound good. If it sounded bad when I bought it, I would've just returned it. I decided to mod the amp for the same reason I modded my guitar and built my own pedals -- because it's fun, and because I feel it lets me put my own personal stamp on my gear and tone.

I know several people have removed the metal grills, but has anyone removed the entire back panel and used the amp as an open back? Was there a pronounced difference? Did you like the change? I'd try it myself, but I'm still waiting to finish up some mods (including waiting for a new speaker to come in).

I know several people have removed the metal grills, but has anyone removed the entire back panel and used the amp as an open back? Was there a pronounced difference? Did you like the change? I'd try it myself, but I'm still waiting to finish up some mods (including waiting for a new speaker to come in).

With the grilled back panel or without any back panel - didn't hear any "voila!" change of tone. I've been working on the chassis so much that I just leave off the back panel AND the chassis screws. :mrgreen: :cool: :lol:

I had put one of these in the shopping cart at http://www.music123.com/ this morning, but did not order it. Thinking it would not be there, I tried the same thing this evening and it came up as "sold out or... no longer available." So I checked my shopping cart and it was still there from this a.m. I ORDERED IT!
AMS has some listed now, but they are $699.00.

I've got a couple more on "special order" at M123 ... we'll see ...

I've got a couple more on "special order" at M123 ... we'll see ...

Yep. Mine is on back order. I do hope they come through.

GA-5 problem ... and solution.

Weeks ago I posted that after lotsa active and aggressive "testing" I had damaged the stock Sig 8 speaker - it was farting out with a heavy attack, particularly on the bottom end.

The new Weber 8F150 speaker arrived and, yep - same problem, farting out when pushed hard. Something had happened, or was happening, with the circuit.

After going over the mods already accomplished, doing a buncha testing, and conferring with Paul, there were several things to try.

What I did first was to add a 1.5k resistor between the preamp socket pin 7 and the shielded signal wire off the vol pot. This is the way some of the stock GA-5 amps are setup. Paul thought it might have been added by Gibson to cure some parasitic issues. Well, it fixed my GA-5, no more farting out, and the tone really blooms out as both the Jupiter caps and Weber are "breaking in".

Something to take note of and keep in mind if yer GA-5 develops a severe case of "gas".

Well, I swapped a 70's Aria tele thinline for a NIB GA-5 today. Got it home and did the trinity mods plus bumped the first filter to 30uF. Much better, no sparkle at lower volumes tho so I added the 22pF cap to the volume control. YES!!!!

I built a Weber 5F2A last year and never got it to sound as good as this amp. I have an alnico Sig10S I'd love to cram in there.

I've got that 8A125T on order, but I should have also ordered out that Chicago Vintage CAV8 to try out - that could be a killer cheap GA-5 speaker. I heard a GA-5 with a Brit AlNiCo Blue Pup - NICE! - cheap, too ($35).

GA-5 problem ... and solution.

Weeks ago I posted that after lotsa active and aggressive "testing" I had damaged the stock Sig 8 speaker - it was farting out with a heavy attack, particularly on the bottom end.

The new Weber 8F150 speaker arrived and, yep - same problem, farting out when pushed hard. Something had happened, or was happening, with the circuit.

After going over the mods already accomplished, doing a buncha testing, and conferring with Paul, there were several things to try.

What I did first was to add a 1.5k resistor between the preamp socket pin 8 and the shielded signal wire off the vol pot. This is the way some of the stock GA-5 amps are setup. Paul thought it might have been added by Gibson to cure some parasitic issues. Well, it fixed my GA-5, no more farting out, and the tone really blooms out as both the Jupiter caps and Weber are "breaking in".

Something to take note of and keep in mind if yer GA-5 develops a severe case of "gas".

You mean pin 7 right?

Yeah, there had to be a reason some of these amps came out of the box with that resister installed...and you found it!

I just installed the Carling 3-way switch, Jupiter caps and put switches on the bias bypass cap, NFB and tone stack mods.

The switch is nice. It gets the job done and feels great doing it.

The Jupiter caps sound great right off the bat. The amp already sounds slightly less constipated.
These things are supposed to sound even better after several hours?!?!

The switches on the three mods are for evaluation of the mods only. I won't leave them on there.

The fixed tone stack lowers the gain a lot and stifles the sound. The lack of a negative feedback loop and the bias bypass cap make up for that.

With the fixed tone stack removed and no other mods, the amp has a lot of gain (for what it is) and is somewhat shrill.

Removing the bias bypass cap reduces the gain quite a bit without messing with the tone much.

Adding the NFB resistor lowers the gain even more.

So far, I like the amp best with the tone stack removed (mod), the bias bypass cap in place (stock) and the NFB resistor (mod). For me, it's the right combination of gain and control.

I don't like the bias bypass cap removed and NFB resistor in place. The amp is too polite.

I'm going to leave the switches in place for a few days and reserve the right to change my mind on the bias bypass cap and NFB resistor mods.

Now for some smaller filter caps...

You mean pin 7 right?

Yeah, there had to be a reason some of these amps came out of the box with that resister installed...and you found it!

Oops, yeah - pin 7 - I had too much NFB thinking going on at the same time. :roll: :mrgreen:

"but I should have also ordered out that Chicago Vintage CAV8 to try out - that could be a killer cheap GA-5 speaker"

This is so funny-right after my previous post I surfed over to Weber and placed an order for that very speaker :)

I'm playing catch up here.

The images of the Signature 8 and the Chicago Vintage 8 look precisely the same. Same price. Should I assume that they are the same, and that they both come from overseas?

I'm playing catch up here.

The images of the Signature 8 and the Chicago Vintage 8 look precisely the same. Same price. Should I assume that they are the same, and that they both come from overseas?

Never assume...

The CV8 is made in USA, and have a nicer thiner cone. They are different speakers.

So far as I know all the Webers are made in the US. Sometimes they farm out the Sig series to other US companies. The cone on the Chicago looks like the classic Jensen-style cone and might be deeper. 10w vs. 15w on the Sig. Usually lower power handling=more responsive.

I'm playing catch up here.

The images of the Signature 8 and the Chicago Vintage 8 look precisely the same. Same price. Should I assume that they are the same, and that they both come from overseas?

The prices aren't the same.

The alnico Signatures are $35. The ceramic Signatures are $24.
The alnico Chicago is $50 and the ceramic Chicago is $35.

The frames on the Signatures and Chicagos appear to be similar but the cones are definitely different.

I thought the Signatures were imported.

I have a Weber CVA8 in my 5F1. It is very nice and lively. Its cone is made from the same paper as the older Kendrick 8"s, which I happen to have one of in GA5 Ri.

I also have a CVC8 that is not broken in.

I used Weber Sig 8s quite a bit before the CV8s became available.

The CV8s and Sig 8s are VERY different speakers.

Never assume...

The CV8 is made in USA, and have a nicer thiner cone. They are different speakers.

Thank you kind sir. Appreciate that.

Usually lower power handling=more responsive.

My recent experiences seem to support that. I got the 12F Blue Dogs from Weber in 8 ohm 30 watt for my Classic 50 2 x 12 and they seem real well suited to the volumes I play at, responsive and fairly quick break in. Without tutoring I'd have bought the highest wattage they sold, probably.

The prices aren't the same.

The alnico Signatures are $35. The ceramic Signatures are $24.
The alnico Chicago is $50 and the ceramic Chicago is $35.

The frames on the Signatures and Chicagos appear to be similar but the cones are definitely different.

I thought the Signatures were imported.



This is intriguing. The price on the bigger alnico Webers has jumped a lot. They're approximately twice the price of the ceramic counterpart. And yet the alnico Chicago is less than 50 percent more. I wonder why? Is the clip on an 8 inch alnico speaker less sought after? Supply and demand?

any others have any personal preferences on the CV8 between A and F (C)?

Much obliged.

Guy's, I think I'm going to send mine back. It's a great value for what we paid with these being PTP and all, but I finally got a chance to play a Fender Super Champ XD this today and now I want one.

I wasn't really expecting it to live up to the hype, especially with this amp having a digital pre, modeling, etc., but was really surprised at just how good it sounded. I never really gave the modelers much of a listen as I was quite happy with the clean channel.

Don't mean to heist the thread, but thought I'd share the experience. Too bad this one was already spoken for as everyone is out of stock at the time being, but I'm willing to wait as this is sound I've been looking for.

This is intriguing. The price on the bigger alnico Webers has jumped a lot. They're approximately twice the price of the ceramic counterpart. And yet the alnico Chicago is less than 50 percent more. I wonder why? Is the clip on an 8 inch alnico speaker less sought after? Supply and demand?

any others have any personal preferences on the CV8 between A and F (C)?

Much obliged.

Per TA Weber - "Over the past 6 months, the price per pound of Cobalt, (CO) a vital component in AlNiCo magnets has doubled in price. The sinking valuation of the US Dollar has not helped matters. In order for us to continue to provide the large AlNiCo ring magnet used in such popular speakers as our 12A150, Blue Dog and Silver Bell, we are forced to raise our pricing to match these increases in our costs."

I've got several CV speakers and a pair of CTC10's uses the standard Weber vintage basket and not the one shown in that model's pic on the Weber website. I liked the CTC10 so much I used it to replace a JenNeo 10 in Champster Special. I've gotta order out a CVA8 and check that bad boy out.

I've got that 8A125T on order, but I should have also ordered out that Chicago Vintage CAV8 to try out - that could be a killer cheap GA-5 speaker. I heard a GA-5 with a Brit AlNiCo Blue Pup - NICE! - cheap, too ($35).

I sure like the description Weber has for that Brit Alnico.... can you describe the differences from the stock speaker?

I'm not actually planning to upgrade my GA-5, but that sounds like a good speaker to drop into my Valve Junior :mrgreen:

I sure like the description Weber has for that Brit Alnico.... can you describe the differences from the stock speaker?

I'm not actually planning to upgrade my GA-5, but that sounds like a good speaker to drop into my Valve Junior :mrgreen:

Oh hey...I forgot about Weber's Brit 8" speakers! I'd bet that those would be fantastic in this amp!

Yep. Mine is on back order. I do hope they come through.

I called 123 today and asked about yesterday's order. Not going to happen; they have none and don't know about getting any more.:sad:

I got my GA-5 'Blem' or return today from MF.

Seems to be in perfect order; sounds great so far. Might have to play it like this for a good while to get used to this type of amp.

The serial plate on the back cover ends 0406. Does this mean April, 2006?

No flaws, very pleased indeed.

I was convinced the boat had left without me. How about that!

I was convinced the boat had left without me. How about that!

Welcome aboard! :wink:

...The serial plate on the back cover ends 0406. Does this mean April, 2006? ...

yep.

i just plugged my ga-5 and it really doesn't sound that great. i compared it to my lil dawg champster. i got to mess with some more.

Andre-you should let the amp burn in a few hours before you judge it.

Lafayette...I grew up there.

This is fun!

I like the way I find myself playing things different to fit in the envelope of the little amp. To keep the distortion in that sweet zone.

Just like I am keeping these threaded saddles on this Palo 60's Classic, I am staying stock as long as I can possibly stand it, even if I have to sweat.

I can always turn it down a little more and mike it into one of the big boys.

This is fun!...

See what you been missin'?

And then there's those simple mods to check out ... :cool:

I'm loving mine still, gigging it still, mic'ing it up still....Yahoo! I kept the one electronic mod....the lifting of the 1st stage bypass cap.

2 questions:
#1 What's the story on the changing of the speakers? Why are you folks going with AlNico? I'm not sure what to expect from that swap.

I was also looking at the Brit Series Blue Pups....

#2 What would be the most efficient speaker, one that would give the most headroom and volume before breaking up? The Alnico Brit Series, the CVA8, the CVC8, etc...basically the Weber 8's!

I know it all depends on style, I'm basically shopping for something a little brighter than the stock speaker, that will let me get quacky and punchy rhythm sounds with 2 an 4 positions on my Strat, ala Steely Dan.

Insights?

droo

I'm loving mine still, gigging it still, mic'ing it up still....Yahoo! I kept the one electronic mod....the lifting of the 1st stage bypass cap.

2 questions:
#1 What's the story on the changing of the speakers? Why are you folks going with AlNico? I'm not sure what to expect from that swap.

Diff'rent strokes for diff'rent folks.

I was also looking at the Brit Series Blue Pups....

#2 What would be the most efficient speaker, one that would give the most headroom and volume before breaking up? The Alnico Brit Series, the CVA8, the CVC8, etc...basically the Weber 8's!

Absolutely a big ceramic like the Weber 8F150 - have one in my #1 modded GA-5 and it yields 2 clicks more clean headroom before the overdrive starts.

I know it all depends on style, I'm basically shopping for something a little brighter than the stock speaker, that will let me get quacky and punchy rhythm sounds with 2 an 4 positions on my Strat, ala Steely Dan.

Insights?

I've got an 8A125T coming in a week or so, for just that reasoning - a brighter and smoother overdrive.

droo

....

Hmmm, thanks for the suggests Rob :)

I don't know if I can swing an $80 speaker at this point....I was thinking I could manage the $35 flavor...leaving me with the CVC8, and the AlNico or Ceramic Blue Pup.

Hmmm... fun to tinker, eh?
droo

i just plugged my ga-5 and it really doesn't sound that great. i compared it to my lil dawg champster. i got to mess with some more.

ok guys please don't bash me too hard, i played the ga 5 some more tonight in the garage and i played around with the volume knob...

i had the volume too high the first time on 8 like how i usally keep my champster. I found that around 5 it sounds great! I guess its has more natural gain then my champster.

i want to change out the speaker and do the mods. i guess thats why y'all doin the mods, is to tame the gain some?

anyways i'm very happy with the amp and thankful to uncle rob for hooking me up once again! :grin:

I wonder how this Jensen 8" P8R would sound in the Ga5 heres a sound sample on the top right page http://www.jensenvintage.com/p8r.htm

ok guys please don't bash me too hard, i played the ga 5 some more tonight in the garage and i played around with the volume knob...

i had the volume too high the first time on 8 like how i usally keep my champster. I found that around 5 it sounds great! I guess its has more natural gain then my champster.

i want to change out the speaker and do the mods. i guess thats why y'all doin the mods, is to tame the gain some?

anyways i'm very happy with the amp and thankful to uncle rob for hooking me up once again! :grin:
Reading this thread is is a bit like going back in time 2 1/2 years ago when the Epi VJ came out. There was all the initial excitement followed by the honeymoon and then the talk of mods and speaker changing.

What is different with the GA-5 is that it has an excellent turret board that is simple to modify. What is the same as the VJ are the same circuit problems that rob the amp of tone and produce too much harsh fizzy distortion. The GA-5 and VJ are the effectively the same circuit. So if you want to do some mods to make the GA-5 sound better and also tune the amount of gain, then everything you need to know is available at SEWATT.com in the VJ FAQ.

I would highly recommend anyone that is keen to mod their GA-5 to:
1. Correct the input resistors
2. Replace the 1M voltage divider
3. Remove the tone cap
4. Re bias the pre-amps
5. Tune the bypass caps to taste
6. Add a 1000uF cathode cap on the EL84

- before you start changing the speaker. If the speaker is the same as the one as the VJ Combo (I suspect it is) then it is very well suited to a small combo cab like the GA-5 and the circuit.

I have tried a Jensen P8R which was truly horrible in that amp and also a Weber 8F125 which sounded like a much bigger speaker buy ultimately I found it too boxy and boomy in such a small cab for my tastes.

The mods above should only take about 30 minutes and cost a few dollars. There are also plenty of sound samples on the SEWATT site that demonstrate how good a well modified SE EL84 amp can sound.

Below is a very good primer for anyone wanting to learn about the function of the components and how to improve an amp such as a GA-5.
S2's excellent guide to modifying a VJ or any SE EL84 amp. (http://www.s2amps.com/docs/vj_kit_inst.pdf) This can be used in comnjunction with the schematic below.

The GA-5 and VJ are the effectively the same circuit.

Interesting...

A quick look at the schematics...

1. Different operating voltages
2. Different input resistors
3. Different plate resistors
4. Different power cap configuration
5. Different power cap values
6. Different "fixed tone circuit"
VJr - 1M resister in series with 1st coupling cap
GA5 - 1M resistor (with 22pf cap) in series with 1st coupling cap
7. Epi has cathode cap on 2nd stage, GA5 doesn't

Plus, the GA5 has better components in it, and a "correct" power transformer that puts the power supply voltages at the correct values for an EL84 amp.

I'm not sure what you see that makes them "effectively the same circuit". I guess they are based on the same simple tube lineup.

All I'm saying is that you are "highly recomending" a whole series of mods to an amp (that you've never modded yourself) based on what other people have done to a different amp with different compnents. The Epi & the GA5 sound different, and will react differently to certain mods.

I generally agree about not being quick to change speakers but I've heard the Weber ceramic flat cone compared to the alnico ribbed cone and the alnico/ribbed is the only way to go for vintage Jensen tone.

... the alnico/ribbed is the only way to go for vintage Jensen tone.

+1

Interesting...

A quick look at the schematics...

1. Different operating voltages
2. Different input resistors
3. Different plate resistors
4. Different power cap configuration
5. Different power cap values
6. Different "fixed tone circuit"
VJr - 1M resister in series with 1st coupling cap
GA5 - 1M resistor (with 22pf cap) in series with 1st coupling cap
7. Epi has cathode cap on 2nd stage, GA5 doesn't

Plus, the GA5 has better components in it, and a "correct" power transformer that puts the power supply voltages at the correct values for an EL84 amp.

I'm not sure what you see that makes them "effectively the same circuit". I guess they are based on the same simple tube lineup.

All I'm saying is that you are "highly recomending" a whole series of mods to an amp (that you've never modded yourself) based on what other people have done to a different amp with different compnents. The Epi & the GA5 sound different, and will react differently to certain mods.

Gee is correct. They are effectively the same circuit. Only they've been tweaked in different ways, and the GA5 has higher quality components.

Where I differ from Gee is with these comments...

1. Correct the input resistors

The input resistors are "correct". If you want to change the input to be like a 5F1, there's nothing wrong with that. But the way it comes from Gibson, more like the vintage GA5 is not incorrect.

2. Replace the 1M voltage divider
3. Remove the tone cap

The 1M resistor and 22pF cap in parallel with each other, comprise a simple high pass/low cut filter designed to strip some of the bass out of the signal. It can be defeated by jumping across it, or replaced with a straight wire, or left in place if you prefer the tone with it in.

The 1M in parallel with the volume pot serves to reduce the volume pot's value to 500k and make the taper more linear. It could be removed if desired, but the volume control is already pretty "fast".

4. Re bias the pre-amps

Again, if you want to set it up more like a 5F1, that's fine, but the way the preamp is setup from Gibson is like the vintage GA5 and sounds fantastic.

6. Add a 1000uF cathode cap on the EL84

I can't imagine what this would accomplish. Gee, can you tell us what would supposedly be gained from this?

Gee is correct. They are effectively the same circuit. Only they've been tweaked in different ways, and the GA5 has higher quality components.


So, at what point does "tweaking" a circuit make it "effectively a different circuit"?

The two amps have circuits that operate the same tubes at different design points with different voltages. That (IMHO) makes them "effectively" different amps. Which is probably one reason why they don't sound the same.

When the circuits of the two amps operate the tubes differently, I would expect the modifications to affect them differently.

Gee's assertion that they are effectively the same, and that therefore people should mod them the same way for the same results is silly.
:mrgreen:

So, at what point does "tweaking" a circuit make it "effectively a different circuit"?

Well, at this point we're debating semantics.

The vintage GA5, the GA5 Ri, the VJ, the 5F1, the 5E1, and I'm sure many others, are all the same basic circuit. The "tweaking" is the fine tuning that differentiates among these models, but it's still all the same basic circuit.

Well, at this point we're debating semantics.

The vintage GA5, the GA5 Ri, the VJ, the 5F1, the 5E1, and I'm sure many others, are all the same basic circuit. The "tweaking" is the fine tuning that differentiates among these models, but it's still all the same basic circuit.

Fair enough. :mrgreen:
(And, I do think GEE's links are a good resourse)

So, at what point does "tweaking" a circuit make it "effectively a different circuit"?

The two amps have circuits that operate the same tubes at different design points with different voltages. That (IMHO) makes them "effectively" different amps. Which is probably one reason why they don't sound the same.

When the circuits of the two amps operate the tubes differently, I would expect the modifications to affect them differently.

Gee's assertion that they are effectively the same, and that therefore people should mod them the same way for the same results is silly.
:mrgreen:
My point is that all of the theory, trial and error and hard work has been done to fine tune a circuit like the GA-5.

For example, it was found that if the 1M voltage divider is replaced by a 100K divider, then the tone of the amp opens up. Changing that voltage divider ratio is the easiest way to increase or decrease the gain and is one of the key things to tweak to get the right amount of gain. Changing the input resistor to a low value like 10K also opened up the amp. The 1000uF on the EL84 cathode was a contribution from one of the designers at Marshall. The 1000uF resists voltage change and smooths out the EL84 reducing the fizzy distortion that some people don't like. The 25uF cap tends to make the distortion a bit too flabby so changing this for a 2uF helps greatly. The GA-5 has been built like a Champ 5F1 with the same voltages and low filter caps, however, the EL84 has much greater gain than a 6V6 and it needs controlling to reign it in a bit and to produce the best sound capable from it.

I also speak from experience having built several versions of GA-5's as well as a Bad Cat Mini and Dr Z Mini and Valve Junior. They all share the same circuit more of less and can be tweaked with a few component changes to be one or the other.

...Changing that voltage divider ratio...

Not trying to be argumentative, but what is this "voltage divider" that you speak of? Please point it out on the schematic.

Not trying to be argumentative, but what is this "voltage divider" that you speak of? Please point it out on the schematic.
In the attached schematic, it is R6 and R7, but it is drawn to look different on the Gibson schematic, but it is exactly the same.

There's an annotation on the "Baby Vox" schematic that Gee attached saying that changing the power tube input resistor will change the "presence". What exactly does "presence" mean? I hear it used a lot in describing amp and pedal controls.

In the attached schematic, it is R6 and R7, but it is drawn to look different on the Gibson schematic, but it is exactly the same.

I see.

I can see how this could get confused, but the functions of these two resisters must be looked at correctly. And, the function of R6 in your schematic, and the 1M/22pF high pass filter in the GA5 are NOT the same.

That 100k in series with the signal (R6) is a remedial gain reduction circuit. It is acting as a voltage divider with the volume pot. It actually impedes tone, and is not necessary. I mean, would you stick a resistor in between your guitar's pickup and its volume control? No, because it would reduce the output (which is what the volume control is for) and it would permanently darken the tone (which is what happens when you turn your guitar's volume control down, which is what all of the various treble bleed circuits on volume controls are trying to overcome). These same concepts are the same with amps as well. So sure, decreasing that resister's value will brighten the tone and increase gain, the same way turning your guitar's volume to "10" will increase its output and likely sound brighter than when the control is turned down. Removing R6 completely will allow the full signal to the volume pot, which will sound best as it will not be impeding the signal/tone in any way.

The 100k in parallel with the volume control (R7) works to limit the full range of the 1 meg volume pot. This limits it's value when turned to "10", which ultimately controls how loud the amp can be cranked up. With that 100k in place, the value of the volume control is effectively a bit less than 100k, which limits the amp from being cranked very high. With the value of that resister increased or removed, the volume control has more range, and can be cranked up higher. Adding a resister in parallel with a pot is an ages old method of creating "effective" pot values where actual values of pots don't exist.

R7 also effects the taper of the volume control. So this method also allows to turn an audio taper pot into a linear taper pot, or a taper somewhere in between the two types

Again, both resistors are acting as kind of remedial "governors", that would not be necessary if too much gain were not being achieved elsewhere in the circuit. The R7 is valid to change the effective value of the volume pot and its taper, but at values as low as 100k it is simply a remedial governor. It and the volume pot could be replaced with a 100k linear taper pot, and you'd have the same thing.

In the GA5, the 1M and 22pF in parallel with each other are acting as a high-pass filter. The 1M blocks part of the signal from getting to the volume control (acting as voltage divider with the volume pot), but the 22pF cap allows the treble to bypass the 1M unaffected. This is a simple "tone shaping" circuit to reduce the bass and low mids. Changing the values of this cap and resister will change the tone shaping, or it can be removed, as I prefer, which allows the entire signal to pass to the volume control.

The 1M in parallel with the volume pot, is acting to reduce the 1M pot's effective value to 500K. As with R7 in your schematic, it's value could be decreased to reduce to how high the amp can be cranked, or it could be removed to allow the pot's full 1M range to be used. In my opinion, this works well at the effective 500K value, and since the volume control is plenty fast and hot, there is no need to remove that resistor.

Agreed. The mod is to replace both 1M resistors with 100K values to keep the gain the same or to alter the value of R7 to adjust the gain. The Valve Junior uses 2 x 1M just like the GA-5 yet sounds better with 2 x 100K.

Agreed. The mod is to replace both 1M resistors with 100K values to keep the gain the same or to alter the value of R7 to adjust the gain. The Valve Junior uses 2 x 1M just like the GA-5 yet sounds better with 2 x 100K.

This is being used as a "remedial" gain reducer, that negatively effects tone, and would not be necessary too much gain was not being produced by having cathode bypass caps of both preamp stages.

The R6 in the VJ is a general, across the board, gain reducer.

The 1M/22pF cap in the GA5 is a high pass filter. Sure, it also effects gain because it reduces the bass part of the signal, but R6 in the VJ and this filter in the GA5 are not serving the same function.

R6 and R7 are not acting as a voltage divider. R6 does act as part of a voltage divider, along with the volume pot. R7 acts to change the value of the volume pot.

With R6 limiting the amount of signal that gets to the volume pot, and R7 limiting the range of the volume pot, the two resistors are working at two different, but related functions.

This is being used as a "remedial" gain reducer, that negatively effects tone, and would not be necessary too much gain was not being produced by having cathode bypass caps of both preamp stages.

The R6 in the VJ is a general, across the board, gain reducer.

The 1M/22pF cap in the GA5 is a high pass filter. Sure, it also effects gain because it reduces the bass part of the signal, but R6 in the VJ and this filter in the GA5 are not serving the same function.

R6 and R7 are not acting as a voltage divider. R6 does act as part of a voltage divider, along with the volume pot.
I don't disagree. Yet the standard mod in the VJ even for the versions without a cap on the second pre amp, is to replace both 1M with 100K. Then you may find you don't need the extra cap across the 1M. The smaller the number of components that the signal passes through and the lower the resistance of those components is, the better the overall signal will be.

But, hey there are many ways to skin this cat. I'm just throwing out the highly evolved mods that are already out there.

Here is an example of what that last version of the VJ (Baby Vox) I posted, sounds like as an example of what a modified circuit can sound like.

Tele played through Baby Vox mod SE EL84 amp. (http://www.davidvibert.co.uk/BabyVoxTele.mp3)

And isn't about time that we get some samples to listen to here. How can this thread grow so big without someone posting what it sounds like?

There's an annotation on the "Baby Vox" schematic that Gee attached saying that changing the power tube input resistor will change the "presence". What exactly does "presence" mean? I hear it used a lot in describing amp and pedal controls.

That R15 is yet another "remedial" gain reducer. The higher its value, the more it will interfere with the tone.

The more I look at this Baby Vox schematic, the more bizarre it seems.

Too much gain is being produced by the first preamp stage, so its output is reduced by R6. Too much gain is being produced by the second preamp stage, so it is being reduced by R15.

If the value of R2 was increased, and C4 removed, the output from the first stage would be more manageable, so R6 could be removed. And if C3 were removed, the output from the second stage would be more manageable, so R15 could be removed.

The 1K resistor it prescribed on the power tube screen is not necessary, because R12 is already serving that function.

And the value of 47uF for the preamp filter, C8, is incredibly high. The .1uF C11 is interesting as well.

Going to DC for the filaments is sure a fantastic idea.

The smaller the number of components that the signal passes through and the lower the resistance of those components is, the better the overall signal will be.


I agree completely.

But, hey there are many ways to skin this cat.

I agree here as well, but I'll add that some ways are better than others, and some require additional, unnecessary "skinning".

And isn't about time that we get some samples to listen to here. How can this thread grow so big without someone posting what it sounds like?

I couldn't agree more!

I need to get set up to record some clips myself.

...
And isn't about time that we get some samples to listen to here. How can this thread grow so big without someone posting what it sounds like?

Yeah man, I gotta work on some sound bytes ...

[QUOTE=Gee;1175299]Here is an example of what that last version of the VJ (Baby Vox) I posted, sounds like as an example of what a modified circuit can sound like.

Tele played through Baby Vox mod SE EL84 amp. (http://www.davidvibert.co.uk/BabyVoxTele.mp3)

From what I can tell on this computer, that sounded very tasty! Very nice!

For little fellas I have a Blackface VibroChamp Clone from Ceriatone! It currently has an AC Hum that I have to look at but apart from that it is an awesome little amp. Just waiting on a custom 12" (yes 12) cab.

Like Boris, I just received my '06 blem from MF and am digging it just the way it is. Thus far, I like playing it a little dirty at 4-6 volume (or 11-1 if you call straight up 12 o'clock).

I noticed today that input 2 is a little quieter than input 1. Who here knows how #1 is wired? Is that a useful channel, or just stay with #1?

(e.g., does 2 work best for humbuckers, mic, etc.?)

I'm sure I will try these mods sometime. For right now though, I have a happy little amp and owner.

Like Boris, I just received my '06 blem from MF and am digging it just the way it is. Thus far, I like playing it a little dirty at 4-6 volume (or 11-1 if you call straight up 12 o'clock).

I noticed today that input 2 is a little quieter than input 1. Who here knows how #1 is wired? Is that a useful channel, or just stay with #1?

(e.g., does 2 work best for humbuckers, mic, etc.?)

I'm sure I will try these mods sometime. For right now though, I have a happy little amp and owner.

I'm not trying to be dismissive of you, but almost everything you could want to know about this amp and more can be found in here somewhere: http://www.tdpri.com/forum/amp-central-station/99134-%24299-gibson-tube-amp-made-usa.html

Like most every other amp that has two inputs per channel, it was never intended that anything be plugged into #2 unless something else was already plugged into #1. The fact that #2 is lower in gain when used by itself is just a product of the design. If you like the sound, nothing wrong with using it.

Joe...welcome to the hip-est thread around! I have been just so overcome with knowledge...I never knew :)

Anyway, I've been pretty successful with using only input #1 with singles or buckers. #2 is nice, but lower volume and dynamics.

I've done one mod to this amp, the lift of the first stage bypass, and gotten a bit more headroom and less "over the top" distortion. I highly recommend this mod. Read this whole stinking thread, all 700+ posts. It's amazing.

What I've found useful, especially for buckers, is an eq pedal in line. I gig this little guy and use it as a monitor for me....sending it through the PA. It's a dark little amp in stock form, and the bypass mod, while giving a tad more headroom and taming the distortion beast, doesn't change the fact that it's dark to begin with. A speaker swap may be in order. I had a modded Boss GE7 laying around, and now I use it to tweak those parameters I either need, or lack.

Works for me, and my bass player loves this little fella. I'm a fan of gigging this guy...you want a Scofield grind? This is it. And at decent stage levels too boot!

droo

Like Boris, I just received my '06 blem from MF and am digging it just the way it is. Thus far, I like playing it a little dirty at 4-6 volume (or 11-1 if you call straight up 12 o'clock).

I noticed today that input 2 is a little quieter than input 1. Who here knows how #1 is wired? Is that a useful channel, or just stay with #1?

(e.g., does 2 work best for humbuckers, mic, etc.?)

I'm sure I will try these mods sometime. For right now though, I have a happy little amp and owner.


I hear that. It would seem to me that turning the knob beyond that just makes it fizzier.

I think it sounds better with the single coil pickups than the 'bucker.

I am fascinated that you can go from clean to dirty just off the pick attack.
It is a gas; I admit I was kinda dismissive of what I called 'practice amps' for years. I wish I'd discovered this sooner in my life.

Pete-I had a Ceriatone 5E3 that hummed until I separated the preamp and power amp grounds. Star grounding everything together was the problem in that amp.

Anyone want my GA-5 before I send it back? I've got a Fender Super champ XD on the way which is more to my taste. I did the first mod, but can solder it back (which I will have to anyhow before I send it back) or leave as is, your choice.

I've had it for about three weeks. Let me know. $300 + actual shipping charges from 78414 via FedEx for UPS. Money order or Paypal (3% fee for Paypal).

I used an alligator clip temp jumper to test the sonics that results thru the jumper mod in the "trinity". That mod was going to shred the stock speaker. I am trying to keep this amps overall volume at dbs that are almost "office" quiet and that mod really opens up the volume...just pulled the gator clips off and back to "normal". I ordered a Weber Blue Pup to see if that will tame the overall rumbly-dark sonics of the GA-5. At $50 with shipping, I hope I don't find thta I should have paid the extra and got a 8A100T! Only experimenting will tell.

Btw: (Juan & Jesse signed off on my GA-5 Nov. 22, 2006).

When these amps get to vintage age, will all of the mods diminish the value of these amps?

I used an alligator clip temp jumper to test the sonics that results thru the jumper mod in the "trinity". That mod was going to shred the stock speaker. I am trying to keep this amps overall volume at dbs that are almost "office" quiet and that mod really opens up the volume...just pulled the gator clips off and back to "normal". I ordered a Weber Blue Pup to see if that will tame the overall rumbly-dark sonics of the GA-5. At $50 with shipping, I hope I don't find thta I should have paid the extra and got a 8A100T! Only experimenting will tell.

You should test out adding the NFB resistor - that could be just what ya need. Personally, having heard the 8A100T and the Blue Pup, I like the Blue Pup much better. I've got an 8A125T coming - hey, it's all a crap shoot of sorts because of what each of us expects to hear, and if mods were done to the circuit.

Btw: (Juan & Jesse signed off on my GA-5 Nov. 22, 2006).

When these amps get to vintage age, will all of the mods diminish the value of these amps?

Ya know, when I first read that I thought "is he nuts?" but given the history of Fender, and that beat up '56 Tele I bought used in '59 that I GAVE AWAY in the late 60's, who's really nuts now?!?!?!? :roll:



....

Has anyone tried swapping out the 25uf cathode bypass cap for a .68uf mallory? If I understand, that will reduce some of the low frequesncies form ulimately getting to the speaker.

What effect will changing the 22uf/350v filtering cap to a 30uf produce?

Thanks, glad to hear that the Blue Pup seems to be the stronger choice...I'll have a better idea in a few weeks. Ted replied to me and confirmed that these speakers are made at his facility in IN.

I am sure I saw your Tele at Christi's in New York! Sorry 'bout that :-)

Hey y'all I love the first of the trinity mods, snipping the 25uf cathode bypass cap! Didn't care for the jumper mod. Thought the amp or speaker was fizzing out so I did with out the jumper. Not into the NFB cause i likes my treble!

Just order a ceramic british blue pup speaker for my GA-5! I want the treble and dynamics the speaker offers like it explains on ted's web site!

My point is that all of the theory, trial and error and hard work has been done to fine tune a circuit like the GA-5.

For example, it was found that if the 1M voltage divider is replaced by a 100K divider, then the tone of the amp opens up. Changing that voltage divider ratio is the easiest way to increase or decrease the gain and is one of the key things to tweak to get the right amount of gain. Changing the input resistor to a low value like 10K also opened up the amp. The 1000uF on the EL84 cathode was a contribution from one of the designers at Marshall. The 1000uF resists voltage change and smooths out the EL84 reducing the fizzy distortion that some people don't like. The 25uF cap tends to make the distortion a bit too flabby so changing this for a 2uF helps greatly. The GA-5 has been built like a Champ 5F1 with the same voltages and low filter caps, however, the EL84 has much greater gain than a 6V6 and it needs controlling to reign it in a bit and to produce the best sound capable from it.

I also speak from experience having built several versions of GA-5's as well as a Bad Cat Mini and Dr Z Mini and Valve Junior. They all share the same circuit more of less and can be tweaked with a few component changes to be one or the other.

How close does the Gibson GA5 and the Dr Z Mini Z Combo sound to each other and which one sounds better out of the box

I used an alligator clip temp jumper to test the sonics that results thru the jumper mod in the "trinity". That mod was going to shred the stock speaker.

You simply can not use an alligator clip jumper to do anything in the preamp signal path of a tube guitar amp, or most any audio gear for that matter. Circuits like that are far too sensitive. Those clips and the wire hanging off there would generate who knows what, probably causing parasitic oscillations and who know what other severe nasties. Never do that.

If you are going to try that mod, the "slackest" way you can do it is to solder a short jumper wire across the 1M/22pF junction.

Has anyone tried swapping out the 25uf cathode bypass cap for a .68uf mallory? If I understand, that will reduce some of the low frequesncies form ulimately getting to the speaker.

What effect will changing the 22uf/350v filtering cap to a 30uf produce?

I have not done it, but IMHO, consider it the proper way to boost treble without bass, rather than that cheesy 1M/22pF high-pass filter.

Try it and tell us what you think.

The 30uF may tighten the bass a bit.

Good info.

Another good point is the quality of the power suppy, we are all using voltage regulators in order to maintain the proper level of juice, right? The sensitivities of a tube amp will respond to both the high quality of the AC source and low quality of the AC source. The power supply may be picking up and getting cluttered with electronic appliance noise, flourecent lighting noise, garage door opener noise, etc. Some of the sonic differences that are being heard by different folks doing the same mods on the same amps maufactured within months of each other, may not so much be a result of the varying amount of solder we used on the connections specific to your amp but to the unregulated and noisy powerline supply. Tripp-lite makes a few good ones that surge protect and voltage regulate. This is a good way to ensure that you are getting high quality pure clean power to the amp. Just another way to spend a hundred bucks to make a 299.00 amp sound better but in the search for that elusive tone, mandatory.

Has anyone tried swapping out the 25uf cathode bypass cap for a .68uf mallory? If I understand, that will reduce some of the low frequesncies form ulimately getting to the speaker.
Excellent mod. Try a few values or even select a few values with a switch. I think 2.2uF works very well. This reduces the bass frequencies early on in the circuit that when amplified can make the distortion muddy. Also helps to make the amp sound less dark yet it keeps the tone fat.

What effect will changing the 22uf/350v filtering cap to a 30uf produce?
It would tighten up the bass and reduce hum. It is even worth adding an additional 47uF cap and resistor and change the other 2 first caps for 47uF. This will give it a more modern sound and feel. Easy to try out.

FWIW, The Bad Cat Mini (SE EL84) has huge power caps - something like 220uF, 100uF and 100uF from memory.

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Quote:
Originally Posted by JamonHamon
Hi thanks for all your help with the GA5 tread
I have a Dr Z Mini Z combo which I like alot do you think the Ga5 and the Mini Z sound alike

In your opinion how close do they sound
Thanks Dale

Hi Dale,

It has been a couple of years since I built a DrZ Mini but from memory it sounded exactly the same as the GA-5 with an EL84 which is the same as the current GA-5.

I have some pictures of the DrZ Mini and the Gibson GA-5 and they look identical. I also believe that they use the same speaker.

Cheers,

Gary

http://i266.photobucket.com/albums/ii243/khelstrom/3h4qauyhexyfcd45obe2t145_Mini-Z.jpg

http://img3.musiciansfriend.com/dbase/pics/products/7/3/8/265738.jpg
The lower photo is a GA-5. Compared to the GA-5, the Dr Z has higher voltages on the pre-amps and has a normal input with a 1M resistor to ground. Should sound more Fendery with the Orange Drop caps. I wouldn't be surprised if the same people who made the GA-5 also made the DrZ. Did Mojo build these?

Could most people tell the difference in a blind test between the GA-5 and DrZ Mini - I doubt it.