A quick PT question

[unparalleled]

Use a 12BH7 as if it's 2 triodes were two separate tubes.
Simplest way is self splitting push pull output like the Firefly amp, but use higher plate volts & phase inverter circuit layout for any triode PP amp.


Here's a little stereo amp you could borrow ideas from:
Shishido 12BH7 Push-Pull Amplifier

Useful site for tube specs:
12BH7, Tube 12BH7; Röhre 12BH7 (12BH7)

[txstrat]

The 2 black wires connect together with the incoming house mains neutral wire. Is this correct?

edit: I reread my post. Yes, primary black on neutral and red on hot (or vice versa, doesn't matter)
Secondary, red on the diodes (in series, not a bridge) and black (center tap) to chassis.

Also, since the pt was designed for 100 and 110v, will modern mains voltage increase the secondary even more than 350-0-350? Thanks for the help

Yes, the more primary voltage, the more secondary voltage. Meter the voltage on the secondary before using any parts which are not rated for the given voltage.

[d95err]

I have 500 volt filter caps. I recall reading somewhere about increasing the 250 ohm cathode resistor on the power tubes. I have a 300 ohm 10 watt. Will this bring down the voltage a little, and is this a good idea?

Increasing the cathode resistor would increase voltages, since the poweramp would be drawing less current, so that would not be a good idea if you are worried about the filter caps.

If voltages are too high, the power tubes may be running to hot. In that case, increasing the cathode resistor can be a good idea, since it makes the tubes run a bit cooler.