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I have tried several amplifiers in my system and they all show transformer hum; (there's no hum from the speakers). Clearly this isn't the fault of the particular amp.The hum often increase after the time the amp is switched on. If music is played at louder volumes, the hum generally gets more pronounced and stays that way even after the volume is reduced.
= What causes this sort of hum?
= Does it harm the amplifier?
= Does it degrade the music? (I haven't noticed this myself.)
= What can be done about it?
Follow Ups:
If you have tried all the things mentioned by other posters and still have the problem you may want to try an AH! AC Offset Killer which you can get from Upscale Audio ($189). It's designed to remove any DC from the AC line which can cause torrodial transformers to hum. It worked for me. You can read about it at Upscale's website. Be advised that this device, if used with a large, Class A biased amplifier will squash the hell out of dynamics as well as get extremely hot. A small amp may not suffer this. If it doesn't work for you I understand that you can ship it back for a refund. You will also need a power cord as this device doesn't come with one.If your amplifier is large and you are interested, I can tell you how I used two of these wired in parallel to bring the dynamics back to life. I have an audiophile buddy who has a Master's Degree in Electrical Engineering from Duke University who helped me with this. It's too long-winded to explain here so if you want to e-mail me I can give you more details. Be advised that the project is not for a novice or faint of heart but it works. You will have to take the innards out of both units and of course blow any warranties that ever existed.
Best Of Luck
Woodrow
FWIW. I fixed this problem at my place by tightening the neutral and ground wire connections in my main circuit breaker box.
nt
Go to breaker board while unit humming, in your case since it is continuous, you won't have to have someone else go while you keep ear to intermittent hum. Turn off each breaker one by one to see which one is carrying the hum. Once you isolate the zone of your house causing trouble, go there and turn off (unplug) each appliance, lamp, etc. In my case, intermittent, it was a light bulb most recently. Tried different bulb brands till it went away. Another time it was bad rheostat, another, a GFI was faulty.Typically, it isn't the equipment, especially my experience with audiophile gear, though I've had a few pieces that it was. On tube equipment, it can often be a tube that does it. Also, redraping wire often can cure it, but in my case, it's now usually something plugged in somewhere in the house hopping mysteriously on the line.
I agree that what you describe sounds to be AC line related. It may or may not be improved with a line conditioner.Look for other devices on the same line or in the area of the amp. Things like halogen lights, light dimmers and variable fan controls can sometimes cause these problems. I would just shut everything in the house off at the breaker box except for the amp circuit and see if it goes away. If it is still there it is possibly coming in on your AC from elsewhere. Even a street light!
If all of the amps you've tried exhibit transformer hum, you may have an AC line problem. Check your AC line voltage. Low voltage conditions can cause transformer hum. If your voltage is below standard, your power utility is obliged to fix it.
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