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

I think you need to verify whether the hum is coming from the amp or from the speakers. If it is coming from the speakers you probably have a ground loop and that has nothing to do with the Mac really... that can be resolved by floating some of the grounds in your system.

If the hum is coming from the amp itself and not the speakers, that is another matter entirely and could either be due to a problem with the amp itself, in which case you should have it checked by a tech, OR it could be a problem with your AC in which case it could eventually cause damage to your amp. If your AC is either too low or too high (but more likely too low) in voltage, the transformers may be humming as a result. You should see if you can verify the voltage of the AC jack you've got the amp plugged into. If it is way out of whack your electrical company should fix it free of charge although that will depend on your geography (here in Chicago they have to provide AC within a fairly strict margin of error or they will come fix it for free) As an absolute last resort you could plug your amps into a line conditioner but I discourage this because I do not like plugging amps into such devices as they typically compress dynamics and have other undesireable side effects.

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

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

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 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.

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.

sounds like something is wrong. All the Mcs I have had never made any noise no matter how hard you listened. It may need to be checked out. Arthur