Mcintosh mc2505 has a hum on the transformer......

99% it is normal. the screws or the nuts on the transformer mounting tends to be loosen-up within the certain time. you should tie them up as tight as possible from time to time and you will decrease the hum significantly if that's the case. you could also use some heavy load on the top of the power transformer. i use the following: felt self-adhesive stickers placed on the surfaces of both solid puck-shape piece of steel(arround 800grams) and the top of the transformer and than stick them together.
the hockey pucks underneath the amp's feet can also help to isolate from the floor and absorb the transformer vibrations.

I fully agree with Arthur! Have your McIntosh amp checked out by an authorized Mac shop. I now have two McIntosh amps, and both are completely silent during operation. I really don't think your 2505 should be making any noise.

Hello,and thanks to all of your suggestions,but I did not make it clear about this humming sound.This sound is not audible with musik what so ever,what I meant is that when the volume is turned all the way up with out input signal I could here some light hum.The transformer sound or hum is heard when the amp is on,but you have to be close in order to hear...I heard it through the grapevine that most of the time Mcintosh transformers usually never go out.What do yall
think?

I wouldn't worry too much on that issue than if it's not audiable with music.

I still think you have something wrong. Get it checked out by someone reputable. Arthur