Amplifier Hum

Could be your furnace, dimmers, microwave oven, etc.. You may want to look at some of the other threads here about hum. Here's a few about amplifier transformer hum:

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1014100392&openusid&zzStehno&4&&

http://forum.audiogon.com/cgi-bin/fr.pl?htech&1013875690&openusid&zzStehno&4&&

http://forum.audiogon.com/cgi-bin/fr.pl?ddgtl&1012613085&openusid&zzStehno&4&&

.......could also be as a result of changes in your local power supply. My McCormack DNA2 amp hums occasionally (fairly loudly), and after long conversations with Steve McCormack (the amps designer), and upgrade to Rev. A, we have concluded that the hum is caused by variations in local power supply-- nothing we can do about it except to complain to the power company. I did, they replaced the transformer I'm on, and the amp still hums occasionally. Good Luck. Craig

The problem could also be that over time with heating and cooling cycles, something such as the transformer mounting has loosen up so check that all screws are tight.

Garfish, I thought you sounded familiar. How's the DNA-2 upgrade working for you?

Here's what I did to eliminate my DNA-2 LAE's transformer hum:

If you narrow the hum down to the amplifier's transformer, try to determine which circuit the amplifier is running off of. Then check the circuit breakers in the service panel.

Chances are that your amps' circuit is on the opposing phase of 115 volts of some or all of your other audio circuits and therefore generating some AC noise that's affecting the transformer.

Have an electrician move all of your audio circuit breakers in the service panel to the same phase of 115 volts.

Just for grins I moved my amp's circuit over to the opposing phase where my other dedicated audio circuits are to see what sonic improvements I may find. No sonic improvements that I could tell but it cured my transformer hum and the transformer has been almost dead silent every since.

And yes, I too have heard the possibility that the mounting of the transformer itself could have loosened as Cford points out above.

-John

John; The Rev. A upgrade sounds fantastic on music-- but still the nagging hum problem. As I need to have an electrician come out anyway, I'll ask him to check phase as you've suggested. Thanks. Craig

I had the same thing happen to me on a McIntosh preamp and turned out to be a faulty power transformer. They replaced that and no more hum.

Craig,

My DNA-2 transformer hums also. I've found that it only hums when one branch circuit in the house is turned on. The circuit is controled by a dimmer/timer. I'm not sure how exactly this might help but try and see is there is any correlation between the DNA hum and other circuits being on. BTW I'm getting my amp upgraded soon, please tell me it's worth it.

John

Sometimes amps hum when they don't know the words.

John; Yep-- the upgrade is worth it, IMO. After upgrade to Rev. A the amp has an incredible smoothness, liquid character, and naturalness that could be described as "tube-like" in the mids and low treble, but it still has the quickness and bass control of a big McCormack amp. Very musical. Cheers. Craig