Do you still have the hum when the preamp is disconnected entirely (with no cable attached to the amp inputs)? Are the pre and power-amps connected to the same outlet ? Just ruling out possible sources of ground loops.
also how old is the amp ? If it's old it could be failing power supply capacitors ? Just a wild guess.
The low frequency hum is almost certainly mains frequency (60Hz), so it's either coming through the amp's power supply, or via poor grounding somewhere.
cheers
also how old is the amp ? If it's old it could be failing power supply capacitors ? Just a wild guess.
The low frequency hum is almost certainly mains frequency (60Hz), so it's either coming through the amp's power supply, or via poor grounding somewhere.
cheers