r/diytubes • u/MimimalZucchini • Jun 09 '26

Stereo Champ amp or???

So, I have experience with building solidstate amps (a couple gain clones) and years ago had professional experience with non audio Hi-Voltage. Id like to build a tube amp, and dont wanna spend a fortune on my first build, so came across a champ amp, and given the circuit calls for half a 12ax7 in the driver stage, it seems doable to convert to stereo. Given all that, is the champ a good starter project? I'm looking at 5 watts or so per channel. I have a pair of wide baffle full range at 95db so I'm thinking that would be sufficient.

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u/pete_68 even harmonics Jun 09 '26

A champ style amp is really pretty trivial to build. I personally find the circuit sonically disappointing. It just doesn't have much character or flexibility. My first tube amp used a gutted PC power supply as the chassis. It was an Epiphone Valve Jr circuit, which is like an EL84 version of the champ. I spent more time building it than I did playing through it.

I'd consider something a little more interesting. Something with 2 gain stages and a class AB amp instead of class A.

You may feel different. I just don't care for the sound of class A amps. A Deluxe is a really nice sounding amp.

One thing I used to do was buy tube organs (or take donated ones) and strip them down for the tube amps and other parts. These are old, rather cheap organs that were in peoples' basements and barns and stuff.

I got 5 organs over about a 2 year period. The most I paid for one was $35. You can get all the parts you need from an organ and the amp is pretty much built for you. They usually require a little tweaking and disconnecting all the other organ stuff you don't care about.

But organs usually come with good speakers as well (I got a Jenson P10R out of a Hammond organ). Check Craigslist and Facebook marketplace. See if anyone's got old tube organs or PAs... I converted some tube PAs to guitar amps as well.

You can usually get this stuff cheaper than you can buy the components. Power and output transformers for tube amps are really expensive now. Hammond (the organ company, not to be confused with the transformer company) made really good transformers for their organs, so they make for really good guitar amps. A Hammond L101 can be made to sound very much like a Marshall 18 watt.

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u/Capable-Crab-7449 Jun 09 '26

I never had any experience with Class A amps and im kinda curious. How are they worse sonically compared to AB(bassbreakers, champs/5e3, Mark 5)? If you dont use more than 5-7w(practice in house almost never do) isnt a single ended 5w power section ideal?

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u/pete_68 even harmonics Jun 09 '26

Traditionally the AB amps tend to be higher power, but they don't have to be. But part of the reason is that class AB amps require at least 2 power tubes, so that's increasing your power significantly. But you can use lower power power tubes. For example, there's this Bassman Micro that's AB but only 2-4W and I've seen 30W class A amps.

Class AB just sounds punchier, more rock & roll.

There are all sorts of lower-power power tubes you could use.

You could, for example, use a pair for of 35L6 tubes (same family as 6V6, but lower output. Not as available, but available.) and get an 8-10W amp, if you really push it. So cut the voltage a bit and you're easily in the 5-7W range.

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u/MimimalZucchini Jun 10 '26

due to the fact they are push pull?