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Amplifier HUM

About 6 months ago I completed building a pair of AudioNote 300B parallel mono block amps. I love the sound, but hate the hum I'm hearing from 15+ feet away. I have gone over and over the circuit, changed the location of wires, re-soldered many points, and done the usual things such as lift the ground wire, and some unusual things such as purchase a PS Audio Humbuster. NOTHING eliminates the hum, or even reduces it. The hum emanates from the mains transformer, and combines with the speaker to produce a most annoying situation. I am using PHY speakers mounted in an open baffle. I don't seem to be as annoyed when I use a "box" speaker. The PHY has a pizzo tweeter, and I've read that that can upset some transformers, but I've disconnected the tweeter, and the hum persists. Any thoughts will be appreciated. Again, I love this speaker/amp combo, but am about to shelve the amps. Thanks.
128x128dawg
Post removed 
6550c
393 posts
 
It is probably a poorly laminated transformer core. The layers are slightly loose and vibrate. Nothing you can do except try a new transformer.

Can you test amp for DC at the output? This maybe the cause of the speaker hum too? Fix It! because DC will damage your speakers.
elevick
2,636 posts
 
Have you tried the amps at another house?
dawg's avatar
dawg OP
15 posts
 
The answer to Veridian's question is that there is both mechanical noise, and an amplified hum through the speakers. It does not change with volume.
dawg's avatar
dawg OP
15 posts
 
I have contacted Brian at AudioNote. He is supposed to send me a new transformer to try, but I have been waiting since April 19th. In his defense he did send me a new transformer about four months ago, but I did not install it immediately, and he asked me to send it to someone else, which I did. I have not checked for DC at the outputs, but will. I have not tried it at another house.
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