$299 Gibson tube amp - Made in USA! - Page 17

red57strat · March 24th, 2008, 09:43 AM

Quote:

Originally Posted by Jack

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.

Rob DiStefano · March 24th, 2008, 09:45 AM

Quote:

Originally Posted by red57strat

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.

Guitarslinger1 · March 24th, 2008, 10:09 AM

Quote:

Originally Posted by Jack

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.

Guitarslinger1 · March 24th, 2008, 10:21 AM

Quote:

Originally Posted by red57strat

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.

GuitarFlunky · March 24th, 2008, 10:52 AM

I thought this amp had reverb. Am I mistaken?

Sevan Simonian · March 24th, 2008, 10:54 AM

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.

Rob DiStefano · March 24th, 2008, 11:00 AM

Quote:

Originally Posted by GuitarFlunky

I thought this amp had reverb. Am I mistaken?

You are major mistaken.

Rob DiStefano · March 24th, 2008, 11:05 AM

Quote:

Originally Posted by Sevan Simonian

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.

KaTaan · March 24th, 2008, 11:13 AM

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

Guitarslinger1 · March 24th, 2008, 11:24 AM

Quote:

Originally Posted by KaTaan

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-centr...ml#post1144412

Sevan Simonian · March 24th, 2008, 11:56 AM

Quote:

Originally Posted by Rob DiStefano

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).

red57strat · March 24th, 2008, 12:15 PM

Quote:

Originally Posted by specialty guitars

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

Rob DiStefano · March 24th, 2008, 12:28 PM

Quote:

Originally Posted by Sevan Simonian

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.

Rob DiStefano · March 24th, 2008, 12:32 PM

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

Rob DiStefano · March 24th, 2008, 08:07 PM

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)

Carling on/standby/off switch (top image) - external 8ohm speaker jack (bottom image)

Ground buss break (top image) - Atom filter caps, Jupiter coupling caps, shielded signal lead (bottom image)

Shielding the inside cab top with alum foil

Shepherd · March 24th, 2008, 09:21 PM

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

Rob DiStefano · March 24th, 2008, 09:54 PM

Quote:

Originally Posted by Shepherd

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.

andrenighthound · March 24th, 2008, 09:57 PM

Quote:

Originally Posted by Shepherd

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!

andrenighthound · March 24th, 2008, 10:00 PM

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

Guitarslinger1 · March 24th, 2008, 10:05 PM

Quote:

Originally Posted by Rob DiStefano

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!

Jack · March 24th, 2008, 10:14 PM

Quote:

Originally Posted by Jack

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.

stephent2 · March 24th, 2008, 10:35 PM

Quote:

Originally Posted by Rob DiStefano

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.

March 24th, 2008, 10:52 AM	#645 (permalink)
GuitarFlunky TDPRI Member Join Date: Mar 2008 Location: Georgia Age: 53 Posts: 28 10 Photos	I thought this amp had reverb. Am I mistaken? __________________ ~Roger~ "Whatever tune I play, I play the way I play it." - Doc Watson

March 24th, 2008, 08:07 PM	#655 (permalink)
Rob DiStefano Friend of Leo's Join Date: Mar 2003 Location: Park Ridge, NJ Age: 62 Posts: 4,622	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) Carling on/standby/off switch (top image) - external 8ohm speaker jack (bottom image) Ground buss break (top image) - Atom filter caps, Jupiter coupling caps, shielded signal lead (bottom image) Shielding the inside cab top with alum foil Last edited by Rob DiStefano : March 25th, 2008 at 06:07 AM.

March 24th, 2008, 10:00 PM	#659 (permalink)
andrenighthound Tele-Meister Join Date: Dec 2007 Location: Bronx NY Age: 32 Posts: 225	uncle rob u still up? I thought ya b sleepin by now..wanna talk to ya u bout the gibson ga5 __________________ "Blues in a doggy bag, is what I got to eat!" www.andreandthenighthounds.com

March 24th, 2008, 10:54 AM	#646 (permalink)
Sevan Simonian TDPRI Member Join Date: Mar 2008 Location: NJ Posts: 19	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.

March 24th, 2008, 11:13 AM	#649 (permalink)
KaTaan TDPRI Member Join Date: Jan 2008 Location: Alaska Posts: 37	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

March 24th, 2008, 12:32 PM	#654 (permalink)
Rob DiStefano Friend of Leo's Join Date: Mar 2003 Location: Park Ridge, NJ Age: 62 Posts: 4,622	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

March 24th, 2008, 09:21 PM	#656 (permalink)
Shepherd Tele-Meister Join Date: Jan 2008 Location: Maple Ridge, Canada Posts: 187	So you have to do all those mods just to get that thing to sound good?