Originally Posted by tomb
Way to go, Eric!
So, how well does it drive those K340's in your pic there? I've heard those things are infamous in their demand on an amp.
Pretty well. 12fm6 didn't have enough gain, so i installed some RCA 12ae6a - which is enough.
Plenty of bass, as others have mentioned. But crystal clear treble, too.
Output is Nichicon KZ 470uf 25v. Even with v+ at 29v and 12ae6a tubes, i actually can't set the tube bias higher than just under 26v, so i have no concerns about their lifespan. Admittedly things would be different w/o tubes or with something wrong in the circuit.
btw, 20-ohm R1 at 29v is running at about 125f. As you can see from my earlier pics, I went up one watt in size, too. It's the hottest thing on the board.
Probably won't be an issue, but if someone was concerned they might be able to get a to220 resistor and heatsink it. Probably have to air-wire the resistor and drill extra holes in the board to mount it.
CA2 are nichicon upw 1000uf, CA9 are CDE polycarbonate 0.68uf. CA3 and CA6 are Nitsuko stacked metalized polyester 4.7uf. They're big and fast - which is good 'cause they're power caps, right? I wouldn't use them in the signal path, but they seem to be doing well on the power rails. CA8 are ERO boxed mylar 0.22uf and nothing special. I might replace these if at some point for some reason I'm dissatisfied with the sound, but by now you know i'm not really entirely a capacitor guy.
RB14 are big honkin ferrites. I have no specs for them - got something like 200 of them, leaded, on tape, on ebay a few years ago.
CA4 and CA5 are relatively cheap Nichicon RS 1000uf 35v. They're good but nothing special. I figure the giant film caps paralleling them make up for any shortcomings they have.
Oh, and the to220 diodes in the power supply are Unitrode SES-5404. They're old-ish. Precursor to the MUR420 iirc. Ultrafast diodes of the early 90's. The voltage drop across them is only about .4v each. Paralleled with unknown-brand .1uf boxed mylar.
I'm driving them with a modified Skynet power brick. Used to be rated 30vdc 1A. Cracked open and pulled out the rectifier board. There's enough room in there that i'll piece together a STEPS-alike AC line filter w/ common mode choke and the works.
With everything biased up and music playing i have almost 33v after rectification, so I'm dropping 4 volts and the regulator doesn't get particularly hot.