I have DC hum in my preamp. I've had it in 3 preamps - all hummed (see this post preamp dc hum). I have a bunch of dimmers throughout the house and part of my trouble-shooting was to turn off every circuit at the main panel except my dedicated 20 amp main system line and still got DC hum in my preamp - grrr. Didn't hear it at one Seattle repair shop when they checked the preamp out. I got new transformer spec'ed similar to the one from the factory but have not tried swapping them yet. I also have a PS Audio Humbuster III on just the preamp and it helps, a little. Guess I will have to do the transformer swap sometime soon or move to another neighborhood (I live in one with a lot of high tech families in Redmond, WA).
My high gain Jasmine LP 2 mk II does not hum at all on the same circuit.
My high gain Jasmine LP 2 mk II does not hum at all on the same circuit.