• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

The "Stupendous" 6P1P 4PP amplifier!

Haha, Bas! Do you have a picture of your other side?
926172d1614290645-stupendous-6p1p-4pp-amplifier-41-ouypkrql-jpg

Sure!
 

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That looks like progress! Good luck.

I was thinking about the appeal of your PCB as a “Universal board”. May I suggest that you consider adding jumpers to separate the halves of the board, so that one could use the boards as originally intended in pairs, but also to just one board for a stereo PPP amp. And add what is needed to enable the use of the boards in triode, pentode and UL mode. I don’t know if it is feasible, but believe there could be interest in such a PCB.
 
Nice, nice, nice. I'm too fuzzy this morning to go back to find your circuit diagram… but how close to the 12 W PA MAX are you running each of the 16 6Π1Π valves? Sigh… ⋅-=≡ GoatGuy ✓ ≡=-⋅

Using the double/tripler/quad board I made, 124V in give 320V out, and (480V or 640V (unloaded))
6P1P running 320V B+ /38mA a piece... (about 10W)

6F12P will do VA/PI with 480V and about 10mA each I think.
 
Using the double/tripler/quad board I made, 124V in give 320V out, and (480V or 640V (unloaded))
6P1P running 320V B+ /38mA a piece… (about 10W)

6F12P will do VA/PI with 480V and about 10mA each I think.

Ah, got it. Looks like (https://frank.pocnet.net/sheets/113/6/6P1P.pdf) around –13.0 VDC on the grid as bias, or VKG thru capacitor bypassed CCS kathode biasing.

Also looks to be pretty near the top-recommended PA limit. But no matter!, that's what bottles do best. As an ol' wire-and-birch friend of me said, “if you're not red-plating, you're not having fun!”.

⋅-=≡ GoatGuy ✓ ≡=-⋅