Capacitance for 4-EL84 Amp?

[The New Steve H]

I decided to build a 4-EL84 amp, using a 270-0-270 PT I needed to put to use.

Question: how much capacitance do I need? I looked at other amps for guidance--notably the Trainwreck Rocket. The caps in that thing add up to 180 uF, which is over twice what you find in a 5F6A.

I'm planning to use a 5AR4 and preamp tubes similar to a Bassman. I would like a little sag.

I don't really know how people decide how much capacitance to use. It almost seems arbitrary. I know they have to be big enough to discharge slowly enough to kill the AC, but beyond that, it's very mysterious to me.

[NickC]

AFAIK the C max of the 5AR4 rectifier is 60uF. HTH.

[xtian]

I'll say what I've absorbed, without looking it up first, and then the smart kids can laugh.

Higher capacitance can mean "stiffer" bass, which I take to mean less sag. Possibly it will be harder to get your desired sag with lots of capacitance.

You can stress a tube recto with too much capacitance.

OK, that's all I remember.

[The New Steve H]

I'm thinking I'll stick a total of 80 uF on this thing and see how it sounds. I can always glom extra caps on later.

Tubes are really crazy. Everything involves a guess or an empirical test.