Driving a small transformer

[Enzo]

OK, I am tired and about to go home to bed, but this thought ran through my mind. Please tell me if I am overlooking something.

Say you had two plates with the same signal 180 degrees out of phase on them - like you would on a pair of triodes in a phase inverter. Would it be possible to drive a relatively high impedance transformer wired between those two plates? For want of a better term, I'd call it differentially driving. Or maybe it is more of a bridge.

Seems like as the plate voltage climbs on one side it is simultaneously sinking on the other, so ther would be a net small current flow through the winding passing back and forth with the signal. At zero signal the voltages would match, so ther would be zero flowing through this winding.

Perhaps it would require lowr resistance plate loads that usual and maybe higher current tubes. But that is details. Or is that the killer point?

it is not a matter of whether something else would do it better, I just wonder if it would work at all. And no, I don't know just what I would use it for.

[Steve Conner]

I take it you mean a transformer without a center tap connected to B+, because if that were the case, it would just be an ordinary push-pull output stage.

If so, well I can't see why it wouldn't work. With no B+ feed through the transformer, you'd need plate loads on the tubes. You could use resistors, like in an ordinary tube gain stage. Or use chokes, in which case I guess it'd be a bridged version of a parafeed output stage.

In either case, I guess it would be limited to running in Class A, because if one tube went into cutoff there'd be no path for the current from the other one. The center tapped transformer allows the same tubes to run in Class AB and give more power.

[Enzo]

Thanks, Steve. No I was not imagining any power output to speak of, and yes there would be plate load resistors. No center tap, right.

I had vague notions of some sort of micropower amp or maybe a line driver.