Champ 600 to 5F1 conversion

[fernando]

mazzas: pictures!! samples!!

[Crawfish]

Originally Posted by mazzas

A-HA!!! Success!!!

So the OT leads were reversed and now everything sounds really nice! I've got some (apparently minor) lead dress to attend to. Only a little hum which seems to go away when I move a wire.

This little amp sounds really nice!

My sincerest appreciation to you, Kevin, for your persistence. I owe you some beer.

Excellent!

I'm dying to see the amp - do you have some pictures? Also, did you go with a tube rectifier?

Thanks for you kind words. Very nice of you to say that.

I'm pretty amazed at the tone too. There is that magical tube 'space' around notes. It's also got harmonics galore, even at fairly low volume.

-Kevin

[mazzas]

I'll post some pictures tonight (hopefully). I'm nervous that it will offer too much opportunity for people to critique my work. But the amp sounds wonderful, so I guess that's where the "proof" is.

Yes, I used the very fine 5Y3GT. The amp is still plenty loud and does not seem to be adversely affected by any resultant sag. On a related note: how come nobody stocks the 5Y3GT tubes anymore??? I can't possibly be the only person who needs them.

I'd like to add a toggle (option) for fixed bias... just to see what it sounds like. I think it might be interesting.

I just picked up a refinished original Bassman head done in blonde Tolex and similar color grill cloth. So next project is a 5F6-A. I'm ordering parts this week. Wish me luck!

At any rate, I can't thank you enough!

[mazzas]

Ok... so here it is. Really, it sounds great. And the whole build can be credited to inspired original post by Kevin. Otherwise, I'd not have gone down this road. I am, however, very glad I did.

A couple of outstanding issues:

1) There is a little bit of hum that I would love to get rid of. Not annoying, but I wish it weren't there. Anyone know if that is possible with this circuit? Or is a bit of hum just inherent in the design? BTW, the SS version of this amp was pretty noisy.

2) I seem to get a slightly "darker" sound out of the High channel. Anyone know what I might investigate to try and resolve the apparent differences between the High and Low channels? Seems to me that the only difference is the resistor across the High input.

Hope you enjoy. I'd be happy to answer any questions.

I had so much fun with this that I'm starting a 5E3 (Tweed Deluxe) for which I've ordered some parts. I believe I had originally posted that I would start my 5F6-A (Bassman) build, but that's going to stay on hold for a short while.

[mazzas]

Originally Posted by mazzas

2) I seem to get a slightly "darker" sound out of the High channel. Anyone know what I might investigate to try and resolve the apparent differences between the High and Low channels? Seems to me that the only difference is the resistor across the High input.

I'm no longer certain that this is the case. I've tried several guitars in both channels and I think that everything is working the way that it should. I believe that I had the volume rolled off somewhat on my guitar at the time I observed this.

[Crawfish]

You did a great job. Looks outstanding. Love the colored board too!

I was going to say in a previous post that after this, you'll get hooked on building your own, but I figured you'd get there on your own.

I just changed the speaker cloth out on mine...I have some pictures somewhere. I think the original is not real attractive and it's pretty heavy to boot.

I can't crank mine up too much when the Missus is around the house. In fact when I was testing it on the bench, after I came up for a breather she was like "think that's loud enough?" Hee hee hee.

For 5Y3s, watch ebay. You can buy small lots of 'em at good prices. I think $3 or $4 or so each is a good deal. Old used ones will last forever. Don't waste your money buying big lots of tubes that are like a "grab bag." You may get a couple tubes you can use and the rest will be TV tubes - pretty much unusable.

-Kevin

[mazzas]

Originally Posted by Crawfish

I was going to say in a previous post that after this, you'll get hooked on building your own, but I figured you'd get there on your own.

I've already stated (with all the hubris I can muster) that I'm never again going to buy an amp, outright.

I've got parts ordered for the 5E3, but I'm really looking forward to building the 5F6-A head. I was very on the fence about what to do next. But the relatively low cost of the 5E3 over other builds that I'm considering swayed my decision.

Thanks for the advice on the tubes. Yeah... I'm a little shocked that the 5Y3's are so difficult to find in stock. Even a reputable local amp repair shop doesn't stock them. Does no one play Tweed era Fenders? Or is it a testament to the relative durability of the rectifier tubes?

I was at the Invisible Sound Sutdio (ISS) open house this past Sunday. In case you're not familiar, it's a recording studio in Baltimore that is also the North American Amp Museum. And everyone is encouraged to play the amps -- they're not just to look at (would they be worth anything, otherwise???).

I brought the amp there and it was well received. Joe, the amp tech, brought out his build, as well (a Blackface era Fender). We all had fun. If you haven't made it to one of these, you might give it some thought. So far, they're small enough events that everyone has a chance to meet, chat, and play guitar together. Maybe about 10 or so people at any given time. Huge collection of Fender, Marshall, and others going back to the 50's... all available to plug into.

[FartherAlong]

Great job mazzas. My stock Champ self destructed and I've just about completed the 5F1 conversion rebuild. I wouldn't even have considered it without this great thread, Thank you Kevin!

[mazzas]

Well... the precedent has been set... let's see some pictures!

[FartherAlong]

I'm in the homestretch! I have a couple of details to take care of, but I should have pictures up in a day or two.

Ed

[FartherAlong]

I finally finished... It runs quiet and cool. Heat might have been the cause of the original amps early demise. It sounds even better than I had imagined it would.







Many thanks Kevin!

[fernando]

mazzas, maybe the hum is becuse the 12ax7 is very close to the power transformer and it is unshielded also...
For the rectifier, it seems that a tube restifier does not add anything to the sound so you could go ss for it. The coolest option imo is to use Weber's CopperCan, so you still have the socket there to use a tube one if you like.
The insides look very nice. Wich speaker?

FatherAlong, it is the picture or did you find a grill cloth of the same colour as the stock one but sound-transparent? Looks very nice.
Wich speaker are you using?

[mazzas]

Originally Posted by fernando

mazzas, maybe the hum is becuse the 12ax7 is very close to the power transformer and it is unshielded also...
For the rectifier, it seems that a tube restifier does not add anything to the sound so you could go ss for it. The coolest option imo is to use Weber's CopperCan, so you still have the socket there to use a tube one if you like.
The insides look very nice. Wich speaker?

Thanks! On your suggestion, I have ordered a shield for the 12ax7... why not? I am hesitant to go with a s/s tone stack after putting the work into getting the 5F1 "the way it should be" (dress and detail, notwithstanding).

To that point... WOW!!! Excellent work, FartherAlong! I've got amp envy.

I was able to work with the lead dress some and the hum is not that noticeable anymore. I will post more as I have additional success, and will update as to the effectiveness of the shielding for the 12ax7, which I expect will help. I'm going to try turning the PT on its side, too.

Speaker is the Weber 6" Alnico.

[fernando]

mazzas, we will be looking to your report

I think that, ideally, you should relocate the pre tube... but let's see if the shield do something...

Also, it seems that having the OT at 45 degrees to the PT helps too, since that way you position the OT on the flux null area of the PT. I've seen this in several projects but in two different orientations: in some, the plates of the OT (side of the OT) are facing the PT at 45 deg., and in some others it's the coil of the OT (front of OT) what is facing the PT at 45 deg, does it make sense?
(I'm an ignorant really, so hopefully someone will correct me or explain it better)

[mazzas]

Originally Posted by fernando

Also, it seems that having the OT at 45 degrees to the PT helps too, since that way you position the OT on the flux null area of the PT. I've seen this in several projects but in two different orientations: in some, the plates of the OT (side of the OT) are facing the PT at 45 deg., and in some others it's the coil of the OT (front of OT) what is facing the PT at 45 deg, does it make sense?
(I'm an ignorant really, so hopefully someone will correct me or explain it better)

According to Weber (the "first" Weber... not the speaker guy) you want to make sure that the orientation of your OT w.r.t the PT is such that they are perpendicular to each other. Mine are arranged as such (along a single plane). But it is certainly worth the effort to try another similar arrangement to see if it helps any.

[mazzas]

Originally Posted by fernando

I think that, ideally, you should relocate the pre tube... but let's see if the shield do something...

Of course, it's the rectifier that sits so close to the PT.

[FartherAlong]

fernando -
The speaker is a Weber AlNiCo Sig 8S. You’ve got a good eye, since I had to make a new baffle to accommodate the speaker I also replaced the grill cloth. The new grill cloth is a lightweight linen that I bought locally in a fabric/textile shop. It’s a cotton and silk blend and it matches up pretty well to the original cloth.

mazzas -
Thanks! But some of the credit goes to Kevin, I just tried to duplicate what he’d done. I had problems with the inline fuse holder ... ahh the smell of melting plastic! After a couple of attempts I opted for a chassis mounted fuse holder instead. I also made good use of a soldering wick on a few ... (several) connections. The amp is quiet but not silent. The original pcb version could be heard at idle in the next room ... with the door closed. The new amp produces about the same level of hum as my other Tweed amp a Valvetrain 5F2. I’m old enough to remember what tube driven radios and TVs sounded like with the volume turned down. I'm very pleased with the results.

Ed

[mazzas]

I have a feeling that my hum is coming from a ground loop problem. I'm going to shorten all the ground wires and install a couple more ground points. Wish me luck. I'll re-post later on to let everyone know how it goes.

Holy smokes, this is good stuff!
http://www.aikenamps.com/StarGround.html

[fernando]

FartherAlong:

Yep, I have a good eye :) I've been looking for such a cloth for long time locally

About the 8'' in the Champion 600: does it sound good? I mean, it is not too big for such a tiny enclosure sound-wise? It's already a bit boomy with a 6'' ...

[mazzas]

For my part, I like the sound of my 6" AlNiCo with the 5F1 circuit. I do, however, also very much like the sound of my Champ played through my 212 extension cab (pair of Jensen P12Q's), but that is an independent issue since it's an extension cab.