Hum from amp - should I worry?

I recently noticed a hum coming from my Meridian 557 amp. I don't use a PLC, so I wasn't sure if that could contribute to the hum or whether the hum is normal. The 557 is, of course, a solid state amp, so this doesn't seem normal to me. Any advice from current 557 owners? Thanks.
is the amp itself humming or do u hear the hum through your speaks? if the former, the hum is likely from the transformer. this is not normal & will likely not b fixed with a power conditioner.
It is the amp itself for certain - not the speakers. I called Meridian and they said something about the transformer coil causing it, but that it wouldn't effect my performance. The hum has actually died down to almost nothing since I made this post, but then again, I'm still concerned. So far, no effect on performance. We'll see. Thanks for your feedback.
I have a Belles 150 A hot Rod, that has a transformer that hums once in a will. According to David Belles this is caused by to much voltage or to little in the power service to my house. I do not know if this is true, but the amp has been dead quite for weeks.
I have a Meridian 557. IT doesn't hum unless I use XLR interconnects without using the shorter plugs into the RCA inputs. If you put your ear next tothe 557 you will hear a slight hum in the unit. Inaudible from a foot away.
Hey, thanks Tap3 & 7671 - I've been listening closely since my post went up and as you said 7671, the hum is now only audible when my ear is pressed against the face of the amp. When I first heard it, it was audible away from the amp, but it only lasted for a few minutes. Maybe there was a power service problem that morning. Who knows - the amp still plays great, but I just hope it's not a sign of something worse to come. Thanks.
Enjoy the 557. It is a great amp that has been missed by the audio industry!! When coupled to the Meridian 502 pre-amp and 508.24 cd player, it is awesome sounding.
7671 - that's the exact same component set-up I are right, the 557/502/508 combo is killer. Now you've got me curious, what's your speaker/cable combo?
Electraglide FatMan on amp and Fat Boys on cd/pre-amp. MillerSound giant speakerwires(kock off of JPS superconductor 2 wires)two separate runs in bi-wire format and balanced Delta Lab silver interconnects on CD to pre-amp and pre-amp to amp.Delta lab power cords on electostatic speakers and line conditioner.