Okay, given the method described on this thread (composite load line class A transitioning to class B), I've been able to do a bit of analysis and I think I have a solution that will work and meet the requirements I've got. So that leads me to the following:
- 8K plate to plate primary
- 30 Watts output (per channel, both channels driven)
- 430VDC to the center taps (this provided from an Edcor XPWR188 power transformer with silicon bridge rectification)
- EL34 output tubes in push-pull
- 220VDC on the screens
- EFB regulated output stage
Power output, on paper, was actually more towards 40 watts with 250 VDC screens, so I needed to reduce the screen voltage down to 220VDC to shrink max power output to something that can be handled by the off-the-shelf new stock output transformers. I intend to use Transcendar 30W models, so I will finally get to try these out for mee self.
I was thinking 8K primary was too high for EL34s, but it actually it works out okay (on paper), and gives max current demand of the output stages (both channels driven) of 370 mA (185mA per channel), which can easily be sourced by the Edcor XPWR188, which supports 500 mA on the HV winding. With this setup, The first 6 watts or so are (supposedly) class A push-pull, while the remaining wattage is delivered through class B operation.
I could easily squeak out more power, up to maybe 45 watts/channel with the same power transformer if I used 4K output transformers, but my son who requested this amp, says it must have a
smaaaaall footprint (I'm thinking 16 x 12 inches), so the smaller the transformers are, the better, while still delivering a respectable 30 watts output.