Which champ to build?

[KX36]

Hi all,

Appologies if we're not supposed to discuss cloning here, but I don't see it written not to anywhere.

I'm contemplating cloning a champ and I wondered if I could get some opinions on which revision to clone. The most popular 2 seem to be the 5C1 and 5F1, the difference mainly being that the 5C1 uses a 6SJ7 pentode for the input. I don't know much at all about champs. I notice a lot of people on the net seem to be apparently buying reissue Champ 600s and gutting them and replacing with what they say is "5C1 spec point-to-point", although I don't know how close they actually are getting.

Is the 5C1 considered a better sounding or more "champish" one than the 5F1? Is it worth the hassle of sourcing out-of-production 6SJ7s (grid-leak biased, so more hassle) which would be more effort to find, more expensive and more microphonic than a 12AX7; or shall I just do the 5F1?

P.S. I've designed and built my own more complex amp before; I'm doing this for fun to try and see how small I can get a tag strip point-to-point build, but obviously I want a good sounding amp at the end of it.

Thanks for your input,
Matt

[Andy Le Blanc]

I'd start with 12ax7, 6v6, 5y3...fairly simple single ended with a tube rectifier.
5e1... If you've not done this type of electronics it'll cover all the bases.
And you can explore and mod for all the tone stacks you can find.

the lead lengths on modern component make P-P difficult.
you'll have to compromise with a parts board, or terminals, and plan around
the tube sockets

[KX36]

As I say, I've built a more complex valve amp before, of my own design with 2xECC83, 1x EF86, 1x EL34 and 1xEZ81. That was a turretboard. I've drawn up tag strip plans for both revisions and I shouldn't really have any problems with either, since there's so few components. My only problem is chosing which one to build, something I would like people's experiences and opinions on (and any common champ knowledge that I don't have, never really having paid any attention to Fender amps before), rather than just trying to pick one from youtube clips

(I also don't see where tonestacks come into a champ build.)

[Zippy]

I'd start with 12ax7, 6v6, 5y3...fairly simple single ended with a tube rectifier.

No need for a tube rectifier - it adds another socket, more parts to find/buy/fail, etc. There's no sag to be had since you're building a SE Class A amp. If there had been solid state rectifiers when the 5F1 was built, I guarantee that Fender would have used it - Leo was very pragmatic in that way.

If you want the lower voltage that many people associate with early era Champs, select an appropriate transformer with the SS recitifier in mind.

Check out the group build Champ projects. There are currently two in the works - one "budget-minded" based on the 5F1, the other with considerable bells and whistles (including larger iron and more power) with a Blackface-style tone stack ala AA763.

"Developing the DIY "Champ" for first time builders"

https://tubeamparchive.com/viewtopic.ph ... 170#164170

"The Eagle Supre - Big SE Amp"

https://tubeamparchive.com/viewtopic.php?t=14349

[Phil_S]

Andy gives wise counsel. You'll get a very nice amp with ss rectification, one 12AX7 and one 6V6. Look at the later AA764, too.

[Andy Le Blanc]

oh heck... if your up for it do vibro champ. I'd still go with a tube rectifier.
There's an impedance relationship associated with the tube that does make
a difference in tone...

[Structo]

True, I think on small amps a tube rectifier does add character and tone.

Makes it a little more complex and expensive because of the tube and socket but I think the benefits are worth it.

[rp]

I built both, just did a 5C1, look for my post from a couple weeks back, I reviewed what I got maybe too thoroughly, but I was having a lot fun with it.

The 5F1 is a killer amp - get it right and it's one of the greats, right up there with the big greats. If you have to have one that's the one, it's the wildest of the Champs, has that run-away, barely on the edge, big swell quality of a great amp. It has that responsive give and take of a great amp. If you build just one and you want a screaming baby tweed go 5F1.

The 5C1 - at least what I got, is much more polite, less gain, less on the edge, but it's really good in it's own right. I've been playing it a lot and I wouldn't do that if it sucked, even a little, even if I built it - I'd be pulling it apart by now.

I used the Allen 8K for my 5F1. Edcor 5K for the 5C1. Don't use the Triode OT for either. Speakers are tough, they really matter. Go 10" instead of 8" much more choices, but for an 8" I settled on a blue pup for the 5F1, still a bit dark. The 5C1 loves my G12-30 70anni, it needs a larger, efficient speaker to come alive I've found.

Voltages matter, spec the PT for vintage Vs. You don't want the CR to stray too far from spec of 470 @ ~40mA. Certainly not above 600 ohms, and I can even hear that. My plate V is 370V with a 560 ohm CR. 360V would have been better I think. I used the Mojo 330Vav PT.

So, about a 275V AC 5C1 PT, 325V Ac 5F1 PT used with a NOS 5y3. And yeh, no reason not to use ss as long as you figure the voltages right.

[KX36]

Thanks rp, that's an incredibly useful answer! I'll go read your thread right away.

I'll probably go for the 5F1, partly because my own DIY amp gets all of its distortion from pentodes (unless I use a pedal to overdrive the input triodes) and frankly if you push pentodes too hard without triodes to balance it out with some even order harmonics, all those 3rd and 5th harmonics add up to something not very musical unless you're playing power chords, and if you push them really hard they start to sound like transistors.

I may end up building both if I can do it cheap enough, since I think it would be really cool to build a tiny point-to-point head amp with 3 big octal valves in a 6"x5" chassis, but I just remembered I have a 10W squier combo amp I think would also be cool to gut and turn into a little champ combo. (Don't know how feasable that'd be since it has no internal chassis, just a PCB floating in mid air held up by the pots)

[Roe]

I prefer the 5e1 over the 5f1

[Lonely Raven]

rp, does the 5C1 have "bloom" to the notes/chords? I think that's what I'm looking for in a clean-to-slightly-dirty tweed amp.

[Phil_S]

oh heck... if your up for it do vibro champ. I'd still go with a tube rectifier.
There's an impedance relationship associated with the tube that does make
a difference in tone...

Now you're talkin' Andy! That VibroChamp has tremolo to die for, even for people who don't normally use it.

[Allynmey]

Build "the beast" version. Marshallized Champ...kicks ass! Search on the forum and you'll find it.

[fopoman]

this it?

[rp]

rp, does the 5C1 have "bloom" to the notes/chords

Not so much, I think I was calling it swell. That was one of my complaints, but I got the 5F1 for that and it's got plenty, so I'm glad the 5c1 is different.

The OP mentions that pentodes alone can sound transistory when pushed. I'm hearing that here. So btwn what I read on web about the grid leak, what I know about big OTs, and the OP's comment I think I understand the 5C1.

I also used NOS molded caps and one pull at the input, tested only for capacitance. Leaky? Doesn't appear so, everything is dead on spec, but I should check this, maybe I'm loosing some gain? Otherwise the 5C1 is a much more tempered amp.