2. amps-preamps
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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
georgehifi's avatar
georgehifi
10,312 posts
 
Yes you are right Al, my bad, I was including the phono, but up to 20db for the line level is not unheard of.

eg:
The CAT line stage: 15.0dB of gain set to Low and 25.8dB set to High.
Balanced Audio Technology line preamplifier gain was slightly higher than the published specification, at 18.7dB

It only takes the OP's power amp 1.4v to clip and he has over 2v from the dac so he does not need and more gain from the output stage of a preamp which in 99.9% of cases comes after the volume pot.

Cheers George
atmasphere's avatar
atmasphere
11,817 posts
 
My comments on voodoo are just that some believe that an active preamp can actually add real musical information that the source isn't providing, this shatters me that some can believe this.

You won't get any argument out of me on this! I am of the opinion though that passives *loose* detail, not that actives *add* it...

I also agree that if you can get by will less gain, so much the better. So we do offer or preamps with no gain in the line stage, just our direct coupled tube output, which has no gain driven by the volume control.

However:

We have had pretty good luck with getting low noise without removing the gain stage in the preamp, even on speakers of that efficiency (we have customers using speakers that are 107db), which is why it is obvious that preamp gain is *not* the problem! **If it were, hiss would be the complaint, not buzz!**

I feel like I did not put enough emphasis on that last sentence but I don't want to yell :)
charles1dad's avatar
charles1dad
10,250 posts
 
Atmasphere wrote,"I am of the opinion though that passives loose detail and not that actives add it".Right! I`ve believe this for a long time. That`s why the common complaint concerning passive/direct connection is less,tonal body,weight,timbre and dynamic presence-drive.These are real musical attributes not colorations.
yingtonggao OP
71 posts
 
Well, guys, this thread just gained another dimension.

I am a firm believer of well-designed active preamps after trying a few passive ones. I do not exclude the possibility of passives work better in other systems, and in return I hope the supporters of passives don't decribe all active preamps as "colored".

The noise I suffered may be related to too much gain, but I've heard systems with more active gain and with the volume pot(s) at maximum, when there's no music playing, the system is totally silent. Modern components easily achieve 100+ dB S/N ratio, two or three of them hooked up in serial should not generate such an audible noise.

Anyway, you guys reply faster than I could try different options. But this thread is very insightful.
atmasphere's avatar
atmasphere
11,817 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.
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