FUQ (eff -yu - cue) - FAQ's with an EDGE

Tagged As: Power Amp

Question:
I'm in the process of doing some preliminary designs for a guitar tube amp. I'd like to have some comments on preamp versus power amp distortion. Should I design for saturation in the preamp and build a power amp that adds as little distortion as possible? Or, should I let the power amp distort the clean preamp signal?

Answer:
I happen to like having a choice between controllable preamp AND power amp distortion. Let me decide, depending on my mood. Ideally, the preamp should be capable of saturation and distortion. Same for the power amp. Then the player has control by simply adjusting the controls on the amp. If the player doesn't want preamp distortion, he doesn't have to turn it to 10. I do not agree with those who say that all preamp distortion sounds buzzy and is only good for dog ears. The right tubes with the right EQ sounds good to me. You don't have to go into high gain big hair distortion if you don't want to. Just a touch of preamp distortion with some heavy power tube crunch is the ultimate, in my opinion. The biggest problem with power tube distortion is VOLUME. A design like the Guytron would be nice. I'd use preamp > single ended power stage > power soak > final output stage. For the preamp, I'd keep it all tube, with channel switching between clean, typical Marshall style high gain, and even higher gain (three channel preamp). Each preamp should have EQ. The two higher gain sections should have gain as well as pre volume. For the initial power stage, I'd use a single ended EL84. Then to the power soak. I'd put line outs after the power soak. THEN I'd go to a dual EL84 PP power amp. That way, you could get any combination of: preamp and/or class A power amp distortion at any volume level; PLUS a combination of the two WITH crunch from the final output stage at volume.