It's possible your interconnect cables are running too close to the power transformer on your tube preamp.
??slight hum from the speakers ?
System:
Usher mini-dancer 2 speakers
Emotiva XPA-1 monoblocks, Emotiva ERC-2 CD player
Mystere ca21 pre-amp
Just received the Mystere pre-amp & noticed a slight hum when nothing is playing, compared to dead silence with my other Emotiva pre-amp UPS1
Is it to be expected with a valve pre-amp??
Usher mini-dancer 2 speakers
Emotiva XPA-1 monoblocks, Emotiva ERC-2 CD player
Mystere ca21 pre-amp
Just received the Mystere pre-amp & noticed a slight hum when nothing is playing, compared to dead silence with my other Emotiva pre-amp UPS1
Is it to be expected with a valve pre-amp??