2. amps-preamps
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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
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
186 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.
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