exotic tube bass amp

[tubby]

i'd like to rig up a class AB bass amp with two of those big boys from the datasheet in the attachment with about 750V on the plates and 250 on the screens. now the datasheet gives an OT primary for class B with 3,6k.

what would be the OT's primary for class AB in the above outlined conditions
and how much plate current (preamp aside) would i need from the PT?

i'm aiming for a very loud and clean sound.

[Steve Conner]

The "Class-B" conditions in the datasheet you mention are really Class-AB, since it shows an idle current of something like 45mA per tube. So I'd follow those conditions, and they give your answers: OPT primary about 3.6k, 560mA plate supply current at 750V, and 80mA screen supply current at 250V.

The idle current is only 33% of the max anode dissipation, so if you think it's too "B" you should simply be able to bias it hotter. But really those conditions aren't too different from an Ampeg SVT, Fender 400PS or whatever.

I saw a guy selling Fender 300PS OTs on Ebay once, one of these might be a reasonable fit, I think they were 3.3k to 8 ohms.

At 300 watts, it will be loud.