Troubleshooting 50Hz noise in phase inverter

[Strelok]

Thanks for this!
I built a reverb and it has hum, I will chek the things you mentioned.
It has a galactic ground en I think the wiring is right but I will look in to it.

Question about reverb: with the special LP-Hammnond TX, does it matter how much impedance the tank has?
I think Mesas tanks have 2 Ohms and my other tank has 8 Ohms, would that make a difference in hum?

Uzerman: thank you for this summary.
Funny thing: looks like AI wrote it.