https://www.diyaudio.com/forums/solid-state/357369-unusual-amp-1987-a-post6384207.html

Output devices:

Exicons single die: does not requires GS capacitor. P/N have the same capacitance.

Exicon double die:  N device reqires 900p extra cap at GS. P/N have different capacitance.

Renesas/NEC:
2SJ162/2SK1058:     N device (2SK1058) requires 150pF extra cap at GS.
                    P/N have different capacitance.

Gate protection diodes are not required here. Included in the transistor (all latfets have them).


Alternative to adding capacitor to N device: different gate stoppers.

Let's say the 2SJ162 has a gate stopper of 100 Ohm and a gate
capacitance of 900pF, the RC time constant is just RgatexCgate=RC time constant,
so 100x900x10^-12=90nS. If we want 'balance' we need a resistance on the gate of
the 2SK1058 that gives the same time constant.
So, Rgate x 600pF = 90nS, solve for Rgate. In this case Rgate needs to be 150 Ohm.
This could be a valid experiment, remove the capacitor and increase R107 to 150Ω and
see if the effect is the same.

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https://www.diyaudio.com/forums/solid-state/357369-unusual-amp-1987-a-post6401307.html

This common based VAS principle used in Vhex+ amplifier as well (with LTP front end).
Vzaichenko named it "current driven VAS" or "current subtraction" approach.
VAS output is arranged as two current sources, looking at each other.
One of them is driven by the current from the single-ended VAS input transistor in a way,
that its current is subtracted from the current, set by the upper CCS's emitter resistor.
The structure appears to be extremely linear and stable.

Its benefits are the follows:

- High immunity to external noises, especially EMF-induced ones;
- Low distortion open-loop - i-to-v (transimpedance) stage is highly linear;
- Low phase shifts throughout the whole audio bandwidth, requiring very low compensation
  for demonstrating high stability margins and resulting in very good - accurate, natural - sound reproduction;
- High enough slew rate by design - "current drive" front-ends easily achieve 150-400V/uS,
  providing high dynamic characteristics;
- This approach gives high speed, linearity and phase of the open loop circuit,
  ensuring good stability margins with the global loop closed.