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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
14 responses Add your response
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jtwrace's avatar
jtwrace
443 posts
 
WOW! This makes two of us. I'm pulling my hair out...

I've done everything that I know of. I even had the electric company put a recorder on my incoming electric line to make sure there isn't something strange there.
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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.
dawg's avatar
dawg OP
15 posts
 
I just checked the outputs with a digital meter. At the 200m setting the reading is anywhere from 00.0 to 00.3. It keeps fluctuating. At the 2 volt setting it is 0.00.
srlaser
17 posts
 
I get a hum in my amp and thru my speakers only when I am running my dishwasher. It drives me nuts.

I brought a Humbuster and I will let you know how it works once it arrives.
roscoeiii's avatar
roscoeiii
1,155 posts
 
I've got hum probs too, that only exist for my 45 tube amp. Not a problem when it is plugged into other folks' systems, so a prob somehow connected with my apt.

Dawg, is the hum present even when the amp is only plugged into the speakers, and no inputs plugged in? That is my case, and the hum satys constant no matter what the attenuator is set to, even turned all the way down...
livin_262002
187 posts
 
I had a terrible (transformer) hum problem in my B&K MC101 preamp and my Integrated Amp. Both units use toroidal transformers. It was a mechanical hum and not the speaker (ground loop) hum. It drove me nuts too, till I installed a DC blocker between the wall outlet and the units. One of the A'goner was kind enough to build me one for a very reasonable price. If you have a good understanding of electrical components you can build one for very cheap. I now use PS Audio UPC 200HB and there's no trace of hum, even when I put by ear against the amp.

Hope this helps.
Post removed 
srlaser
17 posts
 
Nope the Humbuster did not stop the Hum when my dishwasher runs. I do not understand why my dishwasher would cause my Speakers to hum.

Any guesses?
dawg's avatar
dawg OP
15 posts
 
Roscoeiii- I have continued to experiment. Yes, I still have annoying hum with/without any source plugged in. I've also discovered that my APL NWO 4.0 SE player is contributing hum. Further, I have discovered that if I plug the player and amps into a pair of Klipsch LaScalle II speakers, the hum is greatly attenuated, and is not annoying, and they are more efficient than the PHY's. I also have a pair of CAT amps that are dead quiet on the PHY's without any input, although with the APL I get a little hum, that does not really bother me. Perhaps this annoying hum has something to do with the open baffles of the PHY.(?) Have not heard from AudioNote since April 19th, when tyhey send they's send a new transformer.
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