R2 is totally un-necessary. R3 will bleed the whole circuit without any help.
C1 should be smaller. 22uF tops, but 5-15uF would not hurt anyone or anything. Have we learned nothing about the perils of big input caps from the WOO amps and countless Chinese piles of fail? I guess the guy who designed this did not.
R12 should probably be 470ohms. Probably a typo, but it should really be a few LEDs in series. Or a funky voltage source/CCS like Doug uses.
What choice did the designer have for the heater supply? AC heaters? That is not an option in an amp like this - if someone puts in a microphonic tube (but its my absolute favoritest) it will hum like what. This is true even if you bias the heaters well above ground. And then you are responsible for building a $4100 amp that hums when the same tube did not hum in my old amp - it is clearly something wrong with your amp. no I will not try another tube, this is the best tube I have. What? You say its microphonic and I should smash it up with a brick? You are a fool! No, the tube you sent with the amp does not hum, but its a cheap eastern-block tube. This tube was handed down through my family from mr RCA (what the fuck!) himself who gave it to my grand-dad. Yea it was buried in the back shed for a few years behind an old Ford Fairmont, but we could not get the old radio out from behind the car until we got the car working again, and that never happened. As luck would have it the shed fell over in a storm and all I could salvage was this tube and by golly I'm going to use it. In your fucking huming amp. Except your amp hums. so I'm not going to use it. Is now the wrong place to say what filaments? 5ar4 is indirectly heated, with the heater hooked up to the cathode on one side of the heater supply. Tube rectified heater supply? LOL WUT?
Whats with the hate? Its an overpriced amp, clearly. But, that seems to be the overwhelming trend in hi-fi.
I hope anyone with the skills to p2p this takes the extra hour or 3 to design their own thing at least this nice and get some extra pride from that. Anyone who wants to build it on a PCB should sit down for a few hours and learn to wire things p2p then design something better.
I wish the circuit were just a little more interesting so that more people could learn from it though that is a shame.
The DNA stuff is as boring as you would expect.