Hum from amp - should I worry?

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.

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.

7671 - that's the exact same component set-up I have...you are right, the 557/502/508 combo is killer. Now you've got me curious, what's your speaker/cable combo?