Will work on a MK-4!

[WA4SWJ]

Cool! Love that panel meter. Makes it look old school and to me that's fabulous!

Regards,

[TomMcNally]

I lucked out with that meter Ed. It's an RCA, maybe from a radio transmitter, with a voltage scale of 750 and a current scale of 100 ma. Just right for the amp. The selector switch lets me look at main B+, B+ for each channel (after the chokes), individual cathode currents, and B+ on the drivers, and driver cathode current. Just for fun - but it does look cool. I run that amp on a Variac, because the Mercury Vapor rectifier tube has very little voltage drop, plus the Hammond transformers were running the filaments a little hot, so I back it. Sorry to drift off topic on the ST-70 forum - just wanted to have a little fun. Yellow_Light_Colorz_PDT_18

[EWBrown]

(wiping drool off keyboard) Yellow_Light_Colorz_PDT_07

Very Nice! I'm in process of assembling a pair 300B monoblocks, but they're gonna look positively wimpy compared to your amp.

Just "scored" a really nice freebie "dumpster" chassis and it's going to be perfect for another Rev D board (I have one left that is currently unattached, but not for long) THis chassis is 19 inch rackmount, and still a "virgin" so I don't have to do any restorative surgery up front.

/ed B in NH

[TomMcNally]

Good luck with the project ! I've been a little afraid to try a pair of monblocks ... I worry that my skills with sheet metal in the kitchen will leave me with an unmatched pair. I try to build everything very symetrically balanced, but "twins" might be tough.

Funny you mention rack mount cases - I was originally going to build that big (60 pound) 300B stereo amp in an old rack mount computer case. Just yesterday - I looked at a nice, almost virgin gray metal rack case that is only 17 x 3.5 x 4 ... I might try to cram one of the "Darling" amps in that. Or maybe an ST-70 board driving a pair of 6AQ5's !