Are 400V caps stout enough

[Bob Simpson]

for tone stack use in a d-type amp?

I noticed the 6P OD's are at what, 630v, but some of the
other brands seem to top out around 400...

While I'm at it, are 1/2w pots buff enough?

TIA

Bob Simpson

[dave g]

Yes on both accounts.

There is practically no power being dissipated in the preamp (well, apart from the heaters), and 12AX7s are only rated for 300 volts anyway - so coupling caps certainly won't be the weak link if you ever choose to run your preamp voltages past 400

[briane]

and to answer the other question, 1/2 watt pots are fine.

1/2 watt resistors throughout as well minimum. Note that (for many types of resistors), that larger wattage = larger physical size = less noise.

[Smitty]

Pull all of the tubes out of your amp and measure the voltage at the junction of a preamp coupling cap and plate resistor. It's B+1 or ~450V on many amps. That's because there is no voltage drop across the power supply dropping resistors and the plate resistor.

Amps normally don't see this operating condition except on the bench.

Leo ran 400V caps and they're still working fine 40 years later.

There's a safety margin built in. I think it's around 20% in most cases.