Perhaps this should go under Projects, but here's the "finished" 6CG7/6DJ8 headphone amp, although I've got some modern 6922s in place of the 6DJ8s at the moment.
It's pretty much exactly as I had it on the breadboard at the beginning of the year except I've got rid of the cathode bypass cap on the bottom 6DJ8 and star earthed rather than earth buss.
The PSU is a little different as most of my chokes are in the phono at the moment. So using what I had left I've got 600V ct -> humble 1N4007s -> 10H 74R DCR -> 40uF -> 390R -> 94uF Cerafine. B+ is a little high but no problem. Might put another 390R in series with the one already in.
It sounds really rather nice, better than the proto. This could be the absence of the cathode bypass caps, or the PSU, or a bit of both I guess. The response time in PSUD is really rather quick and it definitely sounds very quick to me. Dynamic too. And there's more detail.
Interestingly PSUD predicted 98mV of ripple. I wondered if this might be quite noticeable but the hum is barely audible. The heaters are AC and trying a DC pi filter didn't change the hum so maybe I can just hear the HT ripple? I could try some more L when I have some chokes free, but frankly it's not a problem and it sounds so good anyway I don't feel the need to tinker.
This is the first time I've used 6CG7s and I rather like them. They're 6SN7 equivalents but 9 pin with an internal screen and they're about £5 each nos
The internal screen is supposed to make them sound better than 6SN7s but I haven't compared them so can't comment.
One day I'll get around to a nice wooden case to mount on the mdf and some nice shiny knobs - then everyone who visits will think I have a really expensive amp from a shop.
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