Similar three transistor op-amp found in bass amp

[Crazyyellowfox]

I just realized that there is a very similar circuit to this in my Ashdown practice bass amp...
it's actually a high voltage op-amp made up of two mpsa92 and one mpsa42.
Instead of the dioe, the output is controlled by a negative feedback loop and a 10uf 'lytic
capacitor + resistor to ground on the inverting input.