Developing the DIY "Champ" for first time builders

[jhaas]

I once built an EL34 Tweed style champ with a tone control and GZ34 rectifier - B+ around 385. I also installed a SS diode rectifier and put them on a center-off standby switch so I could switch between rectos.

Granted, the GZ34 won't sag as much as a 5Y3, but my ears can't tell a bit of difference between the rectifiers in this SE amp.

Since you need to go NOS to get a *real* 5Y3, I dunno if requiring an NOS tube aligns with the spirit of the first-timer-easy-build. Seems like it might complicate sourcing and that saving $10 by using a couple UF4007's might be the way to go.

My $.02

[Firestorm]

On the assumption that this would not be an end user's first or only amp (even if it is a first build) you might consider offering the kit as a head and eliminate the speaker cost (or maybe have a head vs. combo option down the road). Champs really do sound neat through 2 x 12 and 4 x 12 cabs. To make that work, you could spec a Hammond Universal SE OT, and an impedance selector to wire three secondary impedance options. I'm not sure if the original Champ OT was air-gapped anyway, so you could even go with the cheaper Hammond Universal push-pull OT. You could spec one bigger than you "need" to minimize the effect of the standing flux. A P-P OT would give you an "extraneous" center tap you could use as an ultralinear tap if you wanted to squeeze an extra watt out of it. I know, this is heresy ...

[Zippy]

that's what I meant

OK. Sorry to make an issue of that.

I - know from a price point the Solid state rec makes sense. I've never heard a champ solid state rectified so I can't comment possitive or negative on it. but I do know the sag and proper rectifier tube makes or breaks a true champ.

Hmmm, if finding a good/correct rectifier is a challenge and has sonic implications, what of simulating a good rectifier with correct selection of sag resistor and SS rectifier? Could it come close enough to be better than a not-so-great tube rectifier, not wear out, and provide cost savings?

[selloutrr]

anything is worth a try. would a variable resistor be practical for the user to adjust the amount of sage?

[Zippy]

anything is worth a try. would a variable resistor be practical for the user to adjust the amount of sage?

I'm not sure whether that is a bell or a whistle...

300-500 ohms is the territory. Put it on a turret to make it real easy to swap out in an experimenter's kit. Same thing with tone caps.

[Firestorm]

It's not going to sag a heck of a lot no matter what you do. Class A after all.

[RJ Guitars]

Sounds like a neat project.

My 2 cents is, make sure that this amp is something that a person will enjoy playing after the building experience.

I know that is a tough prerequisite because you want to keep it simple enough for beginners but have it sound good enough for a decent guitar player to enjoy playing through it.

So maybe the larger speaker is the key here.

I know the few times I have plugged into an original Champ with the tiny speaker I was left disappointed by the sound.

There are really two perspectives I see driving this idea. There is the affordable opportunity for new builders and then the other thought is that for just a small additional amount you can make a players amp.

Lots of good input on this thread. SPST switch and Solid State Rectifier, makes life quite simple for me. I have not found an existing power tranny that I am thrilled with yet, either the specs are wrong or the price is too high. I've finally chosen for Edcor to wind what I want and actually the price and specs are agreeable but the delivery is about three weeks out. Everything else has come into line pretty very well and I am expecting parts to start showing up early next week.

Thanks for the good discussions, it's been enjoyable just to read through the posts and learn a little.

rj

[angelodp]

Found this site that shows a retro-fit for a Champ to 10" speaker

http://frettech.com/champ/

Weber 10F150T

I suppose there are many choices. Would love to get a list of possible 10" selections going.

These guys make special order one from Weber. Nice sounding amps.

http://www.tungstenamp.com/speakers.htm

ange

[rp]

I'm a stickler for authenticity but building my 5F1 w/ for an 8" was a mistake. It sounds so much better through my little 10" bench test cab. Many many more speaker options too. And when you get a speaker that doesn't work well at least you're not stuck with an 8.

+1 on nixing the MC champ OT. It's a wet dog, concur no chime. I used one in AX84P1. Later swapped with an Edcor 10W 5K/8 - night and day. Better on every level. Just a few bucks more. Not sure in Champ, I'm leery of hifi 'too good' stuff in guitar amps so I was hesitant about the M6 Edcor, but my 5F1 has the husky Allen and it's great too.

4/8/16 taps wouldn't affect the cost much and are way useful.

My champ gets real hot, it's a tight little box, the ss is the way to go. It's my understanding SE amps don't sag anyway.

I've played BF/Sf and they're great with their higher voltage but my 5f1 starts to sound harsh above 370V. Taking the CR too far from 470 ohms also sounds bad.

Not sure what model or mods you're planning but IMO the 5F1 is the one and benefits from having no tone stack and no MV. I wouldn't mod it. The AX84P1 I built has TMB and MV and they are pretty useless on an amp this small.

[RJ Guitars]

Yeah the 5F1 is my favorite. Minimal parts count, Simple, and low signal losses. rj

[telentubes]

I also would vote for making this an amp that would be played , rather than simple a "learning how to build and amp" project. Plenty of marginal sounding cheap amps out there already. Champs are cool. If you're looking for folks for a "group build", count me in, even for an additional $10-$50, if that's the difference between something that will be played, or not.

[RJ Guitars]

I also would vote for making this an amp that would be played , rather than simple a "learning how to build and amp" project. Plenty of marginal sounding cheap amps out there already. Champs are cool. If you're looking for folks for a "group build", count me in, even for an additional $10-$50, if that's the difference between something that will be played, or not.

I have found that it's possible to do both for not so much difference in money... Having said that I have ordered two different sets of transformers. In addition to the tranny selection, as I can see the only thing that would add value to the "Players" edition would be the progressive switch and then some select tubes. Chassis, board, small parts, and layout is the same. I'll be curious which iteration becomes the favorite?

Sorry I haven't had much time to post updates on this but everything has been located and ordered now. I am having transformers wound by Edcor for the Top Shelf iteration and using the Allied power tranny to go with the low dollar output trannies.

How do folks feel about punching the holes for themselves? I have blank boxes ordered for round one.

thanks,

rj

[xtian]

How do folks feel about punching the holes

I will pay money for holes.

I burned up my two stepped drill bits.

[angelodp]

Will a step bit going up to 7/8" handle all the holes that are needed.

a

[Colossal]

Will a step bit going up to 7/8" handle all the holes that are needed.

a

Belton octal sockets (you will need one for the 5Y3..if added, and one for the 6V6) require a 1 3/16" hole.