I thought about that amplifier last night...
It has me wondering if we had a means to drive into a load - like a loudspeaker...but into an amp.
Why not make one a modulation transformer in such a fashion that you could pips the audio into the amp - kinda like a push pull - using one channel for each side?
I imagine this would need something like 8 AWG wire (enamled) along a form and tapped...
Then the crazy stuff piped into the dream...
Leyden jars - the old archaic versions of the Electrolytic caps we take for granted today...
Since the power handling of a typical simple electrolytic may be exceeded - thought that the older versions might be safer
There is an anecdotal story that I read as a child ...
And with Kopcicle posting images of toasted rodents...
There's a bit of a humorous chapter in the book about how Ben shocked the world using Leyden jars and a crude vandegraaff generator to demonstrate the power of electricity.
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Couldn't help but wonder if the old "Pickle jar" - would work as your crude cap to inject the audio into your amp?
It might be a good idea to take the covers off that unit and see if you can cut to the chase and see which concepts they've supplied. Either the transformer coil coupling, or capacitor - or something even more exotic for you.
One of the things I had to deal with in an earlier life was Computer power supplies for the PS2 (IBM XT platforms) that required both a positive and negative voltage with a common neutral or ground for the TTL tri-state I see a possibility to use this method to obtain the voltage differences needed for the conversion of an Audio (essentially an AC signal) into a working "collector" or Plate Modulation technique for the push pull design.
It would be prudent to see how they assembled the output network to drive the loudspeakers together.