At the risk of being too obvious - have you tried a cheater plug yet at the amp/current source? If not you should. I would guess that it will reveal that your problem is an old fashion ground loop. Once you know its a ground loop you can take further steps to try to eliminate it, or just leave the cheater plug in place (that is what most folks do provided the pre-amp is grounded).
SPEAKER HUM
I have been playing with a new system. I was driving my speakers with a MingDa MC 34 AB tube amp (75 wt/ch ultralinear 40wt/ch triode) which is powered with 8 EL 34 tubes. It can be used as an integrated amp, and when I used it as such, it was DEAD quiet.
I decided to make a good thing better, and just got the matching MingDa MC 2A3X preamp to go with it. The speaker hum when both are powered up is awful...not that very low level stuff you sometimes get with an amp/preamp set up...but loud enough to hear during quiet passages of musical pieces.
I have been tormented in the past with trying to eliminate speaker hum...any help out there for this system??
Thanks so much
I decided to make a good thing better, and just got the matching MingDa MC 2A3X preamp to go with it. The speaker hum when both are powered up is awful...not that very low level stuff you sometimes get with an amp/preamp set up...but loud enough to hear during quiet passages of musical pieces.
I have been tormented in the past with trying to eliminate speaker hum...any help out there for this system??
Thanks so much