Champ-Based Low Power Stereo Power Amp

[downsizingnow48]

I have used a Mesa Boogie Quad Preamp with stereo effects and a 50/50 stereo power amp, or a 20/20 stereo power amp, for years. I really like the sound of this setup but it starts out loud and gets louder. Lately I have been looking for a low power stereo power amp for good tone at reasonable listening levels. I didn’t find anything on the market. Studying old low power Fender amp diagrams, it occurred to me that a tweed Deluxe is essentially a tweed Champ with an input stage on the front. If the Champ circuit could work as the power section for a Deluxe, why not as a stand alone power amp? So I decided to build a stereo power amp that is basically two Champs in parallel. I put it in a two-space rackmount chassis. Special attention is needed to layout, shielding, and grounding to avoid hum and other problems. The result is a 5/5 stereo power amp that has great tone at lower listening levels. Despite being two single ended amps in one box, the level of hum is extremely low. With both volumes turned all the way up, you have to put your ear right against the speaker cabinet in a quiet environment to identify any hum. It was not very costly. I’d be interested to hear from anyone with similar experience.

[Steve Conner]

Well, I totally agree with the idea, 40 or 100W of Mesa amplification can be a bit of a handful in your living room.

But I don't see how you arrived at the conclusion that the tweed Deluxe is a Champ with an input stage in front, or how that is relevant to what you built. I think what you meant is that tube amp circuits can be split into pre and power sections, which can be mixed and matched, as long as you pay attention to signal levels. I commonly see people doing things like building a SLO clone with a Champ power section so they can crank it up in the living room without blowing the windows out.

[downsizingnow48]

Thanks for the suggestion on the Champ as used in SLO projects, I will look into that. I did some tweaks that I think made the Champ circuit better for the power amp application and will be very interested to compare what I did with other tweaks people have thought useful.

I agree my thoughts on Champ and Deluxe, similarities or lack thereof, are a bit beside the main point of the post. I think what was running through my head was the utility of this circuit which can function well in very different applications.

Again, thanks!