Dealing with transformer hum

I had this problem with Cary monoblocks once. FIND THE LIGHT DIMMER IN YOUR HOUSE! When the lights were dimmed, meaning resistance in the AC line, the transformers would buzz like crazy. That was the problem for me, anyways! Good luck!

Actually, the reason the transformers hum is because DC is getting on the primary of the transformer.

Here is a little quote by the one and only Nelson Pass (my hero) :

"If you are experiencing mechanical hum from your
transformer, it is often caused by the presence of
DC on the line. Usually this comes from some appliance
using current asymmetrically, such as a lamp dimmer.

The hum comes usually from toroidal transformers, which
saturate easily with DC, and when they recover, they
draw an extra pulse of current, causing the noise.

You can put a pair of back-to-back electrolytics in series
with the AC power line to block this, and it works fine.
Makes sure the current rating of the electrolytics is
high enough, and the they are joined at a like polarity,
such as + to +."

If you trace the hum to the transformer you may want to give the above suggestion a try. I insert two back to back electrolytics on the primary in every amp I build as a matter of design, so I never have to worry about this type of caveat.

Liguy, I'm not exactly sure what these electrolytics are of which you speak? Can you recommend a brand or a site I can look up to learn more about these. They sound very promising.

Thanks,

All good thoughts and if they relieve the problem , great , but if all else fails The Ah Offset Killer works very well. I had tranformer hum with a Rotel, then with an Anthem. Ive upgraded to Classe since then and the Classe is dead quiet, but I remember The previous Amps tranformer hum driving me off the wall. If you do a search on google it leads you in the right direction.

There are a couple of things causing transformer hum in my sytem. My RPTV casues a slight amount of hum when turned on, and when my wife is using the blow dryer or curling iron I get a LOT of hum, even though those devices are being used on a completely seperate circuit. I'd be very interested in more info on the "electrolytic" solution as well.