tuner hum ???


I have noticed that when my tuner is off but I have the preamp set to the tuner input that when I turn up the volume I start to get a hum when increasing volume of tuner input when the tuner is off. I do not have this issue with my CDP which has no hum even when CDP is off but on CDP input with increased loudness. Is this a normal phenomenon with tuners or should I get my Magnum Dynalab Etude looked at. I think I may have noticed this same issue with my Jungson tuner in my Jungson system. Do Tuners hum when off but input has juice put through it?
128x128mitchb
With signal of station hum dissappears. The hum is not just masked but dissappears. I checked this out carefully.
It's as if it has to do with the mute function but that is ok as I listen to clear received fm which has no hum. Any ideas why?
Sounds like it may be a ground issue. I had a very similar problem just recently.

Try floating the ground on the tuner.
I actually don't have this problem with my Jungson tuner. This makes me wonder if their is a problem with my magnum dynalab??