First Watt F1, Руководство по обслуживанию

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Here is a simplified schematic of the amplifier:
The principle is straightforward. The circuit is a simple differential pair of
gain Mosfets commonly biased by a constant current source attached to
their Source pins, with the input signal impressed upon their gates. The
voltage difference between the plus and minus input signals causes current
to flow in opposition between the two Mosfets, and this creates voltage and
current at the Drains of the devices (the outputs), where the loudspeaker is
connected. The DC bias current from the bottom constant current source is
divided between the two Mosfets, and is taken up at the output by two other
constant current sources, so that the loudspeaker only needs to see the AC
current variation, not the DC.
If you are familiar with the Zen series of amplifiers published in
AudioXpress, then you will see more than a passing similarity to the Son of
Zen and some later variations, and these articles can provide more
background information.
Of course this is just the simplified schematic. It would work in principle,
but clearly needs more definition to make a real amplifier: