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Preamp Noise with High-Efficiency Speakers

I have Avantgarde Duo Classic Speakers, I hear a very audible buzzing noise whenever I insert an analog preamp. If I run my DAC (AMR DP-777) directly into power amp, the noise disappears. I have tried 4 different preamps (tube and SS), 3 different amps, a bunch of RCA and XLR interconnects, the problem persists. I have tried dedicated power line and two power conditioners (with Multi-wave options) and various high-quality power cords, so far nothing works, and I am forced to run DAC-direct into power amp. The buzz is not very loud but certainly audible enough to be annoying. There's no noise running the same equipment and power source into regular speakers, I am pretty sure it's just the Avantgarde (104dB sensitivity). Please share your solution if you have had similar situations. Thanks!
yingtonggao
atmasphere's avatar
atmasphere
7,068 posts
 
Yingtonggao, what you report is a buzz. But you did not report hiss, which says to me that the gain is not the culprit. There is some hookup (like a ground loop of a poorly shielded cable) which is allowing the buzz to manifest.
yingtonggao OP
65 posts
 
Atmasphere, you are right, I'd call it a buzz, not hiss.
atmasphere's avatar
atmasphere
7,068 posts
 
Yingtonggao, what this suggests to me is what I mentioned in my first post on this thread. It may be that the preamps you have tried so far have troubles with ground loops, but it could also be a problem in the amplifiers. Have you tried any of the suggestions I offered?
georgehifi's avatar
georgehifi
4,966 posts
 
Ground loops are most likely to present 50/60hz "LF Hum", a BUZZ as the OP says he has indicates higher frequency content, this could be rectifier noise, but from 4 separate preamps tube and SS this is not likely.

If the "buzz" raises and lowers with volume control posistion on the 4 preamps, would mean that is eminating from the source. But because the source is dead quite when it is direct to the amp, the source can be ruled out.

If it is a hum and not a buzz you could try this:
If all 4 preamps have grounded mains cable you could try to disconect the earth wire and see if that makes a difference, or if they have no earth wire on the mains try to give it one to the chassis.

Cheers George
atmasphere's avatar
atmasphere
7,068 posts
 
Actually if a ground loop is present it will more likely manifest as a buzz. It is rare to see a ground loop only produce 60Hz!
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