buzz from my new amp???

I just purchased a Marshall AVT20 at guitars center. I like the sound of this amp compared to comparables in the same price range - esp for blues that I play. However, in the quite of my home I noticed the amp has a very audible buzz that I can make louder or quiter by adjusting gain and volume? Is this normal?

It does this even if there is not guitar plugged in, so it's not feedback.

Oh ya, this was the floor model I purchased for about 10% off but and they couldn't find paperwork for it -

Thanks, Brace.

Some hum and hiss is normal. If you have fluorescent lights, a computer monitoe, or a TV set turned on near your amp, they may be adding to it.

You can get a better idea by listening to another identical amp. I find music shops are usually quiet on Tuesday or Wednesday evenings (no string-slingers showing off for each other).

Are you practicing near ANY other electronic devices at all?? and if you are does your guitar have single pickups instead of humbuckers? this is what happens to me, if i plug in my strat (fat strat s s h setup) and i flick on to the neck single i get hum all the time seeing how i have so many electronic do dads in my house here. But other than that play with your gain settings some more till it goes away.

What you said suggests that there is a problem with a circuit in the amp. I've only had this on solid state amps where there are dodgy components/extra wires in there.

First move it to the "least electrical" room in the house - nothing to interfere,as the other guys said, then try it with various bits and bobs plugged in.

If it still hums..time for an expert.

I've noticed that with the 30 watt Valvestates before, on different amps of the same kind. They buzz a lot more than my pretty crappy Marshall 80rcd. Maybe this is because mine is 80 watts, but it is something I have noticed with [articular Marhalls.

Thank you for the suggestions -

microwaves, computers, televisions, speakers (hard wired in some rooms), toaters, electric ovens, clock radio's - my house must be filled with low-level electromagnetic current . . .

When I put the amp in the only room in the house that does'nt have anything going it turns out to be pretty quite, still a slight buzz, but you have to listen closely to hear it. Based on what you've said, I think that is normal? As I move the amp from room to room with an extension cord, I can hear the buzzing increase or decrease in volume!!

Thanks for your help, at this point I am assuming the amp is OK.

As for the amp: This amp can get pretty darn loud and keeps the sound quality - I think it sounds very much like a tube amp - very warm, & bluesy!! The downside - it's a bit pricey for 20W and you must change all of the setting when going from clean to OD channel, etc.,

Brace.

time for a pedal =P