[CaptBubba]

I was looking at this power-amp kit that i have laying about, and the more I look at the circuit layout the more I think "is this really needed?"

I would get rid of the bass/treble controls, but still I am suprised at the complexity. Does the output portion look strange to anyone else or is it just my noobishness when it comes to tube equipment? I understand how it works (how the electricity flows), but it just seems a rather ungracefull way to handle it.

Now, the big question, I've been looking to modify it to add a headphone output. Seemingly I cannot use the output stage in an OTL configuration

What I was considering doing is just scrapping this kit and building a derivitive of the Earmax amplifier, except using the higher-power 6BQ5/EL84 tubes in the White follower so that it would be capible of powering small speakers and low ohm headphones. This would increase the tube compliment to 5, but I would be using the transformer from the kit, which was designed to run 7 tubes. Also I ws thinking about changing the gain valve to a 6SN7. Ok, so the result would be nothing like the mini-jones amp, but that's where I got my ideas from looking at.

Ideas?

 

[jeffreyj]

Not too much there that isn't necessary, IMO. Referring to channel 1 parts only, I'd get rid of C1/R2 (loudness network), ground R5a directly, delete all of the other crap for that bass control (C2, R8, R9, etc.) and go from there. The RIAA network on the phono input is a bit... primitive. A better job of conforming to the curve can be done, for sure. The sound of tubes may have merit in the amplifier, but I draw the line when it comes to putting them in the power supply. Ditch those plate supply rectifier tubes and replace them with some silicon, bypassed with a series RC network if you want to preserve the "sloppy knee" characteristic of the tube rectifier (which some people claim improves the noise performance - some people also smoke crack...)

Good luck, and don't let that B+ line get you

 

[CaptBubba]

Heh, silicon devices weren't around when this amplifier schematic was made.