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.
dawg

Showing 4 responses by dawg

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.
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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