#1
Hey, I'm running a Marshall DSL100 into a 1965B cab (early 80's). Once I turn the standby switch on, hum occurs regardless of volume levels, etc. It just has to be plugged in and turned on for hum to occur. Unfortunately it will be difficult for me to troubleshoot this with additional heads/cabs. Any ideas on what I could do to fix/eliminate this? A noise gate would only kill hum while I'm not playing but it would still be there when I play, amirite?
#2
Try plugging into a different outlet or if you have a ground lift switch on the back of your amp try switching that. Any flourecent lights in your house could be the 60 cycle hum we all hate.
My Gear
Fender Strat ('97American Lonestar HSS)
Ibanez RGTHRG1
B-52 AT100
Marshall1960A Cab
Marshall 1960B Cab
#3
Judging from the soundclip on wikipedia, it doesn't seem to be 60 cycle hum. It seems to be an octave higher and much smoother. But then again it is the exact pitch and I had it with my Fender, so maybe it just sounds rounder through this setup.

Suggestions for 60 cycle hum?
#4
If you're playing a guitar with single-coils, shield it. Try a different outlet, or turning off/unplugging some appliances that are on the same circuit. A power conditioner could help if it's the wiring in your house that's causing the noise.
#5
Furman power conditioner. don't plug into the same circuit as any flourecent lights. Could also be a tube problem.
My Gear
Fender Strat ('97American Lonestar HSS)
Ibanez RGTHRG1
B-52 AT100
Marshall1960A Cab
Marshall 1960B Cab