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Got Noise?

OK Guys, need your help with this one. Recently I've noticed a fairly high degree of background noise (sounds like a "ffffsss" coming through my system at idle. The noise is only audible when the amp is turned on, not any of the other components. The amp has been tested by the manufacturer and he reports no issues. (Amp is a Modwright KWA150 and I asked Dan to check this for me when he did the "SE" upgrade a month or so ago). The level of noise is audible when I am playing music only at very low volumes, which has been the case over the past 4 months since we now have a baby on board. In fact, it is possible that nothing has changed but the simple fact that before the baby I was listening at higher volumes and did not notice the background noise. On the other hand, it is somewhat intrusive and if there is something going on elsewhere then I'd like to address it. FYI I have a 20 amp dedicated line to my system and have an Environmental Potentials 2050 surge suppressor/noise cancelling device installed on the panel, which I had my electrician confirm has been correctly hooked up. Is it possible that something is happening at the pole where I have a transformer shared by two other neighbors? I can't decide whether this is a new problem that has developed or simply an old problem that I did not know was there until I started listening at much lower levels in the past few months. Tell me, when your system is at idle how much noise do you hear when you put your ear to the drivers? Or from your listening position?
dodgealum

Showing 4 responses by dodgealum

dodgealum OP
1,398 posts
 
Excellent suggestions guys. Let me work through some of your ideas and I'll get back to you with results. Thank you!
dodgealum OP
1,398 posts
 
I played around a little last night and here is where we are:

I confirmed that the noise is ONLY present when the amp is on. I can turn on any/all other components and don't hear the hissing sound. Disconnecting the amp from the rest of the components (ala Mofi) eliminated the noise. That leaves the IC's as a prime suspect and me with a possible answer to the problem. I'm using balanced/unshielded Empirical Design 422 interconnects AND they are (by necessity) routed very close to the 4 gang outlet box where all of the components are plugged into the wall. In fact, one of the wires is literally resting against the power cord for the amp about an inch away from the XLR connector. (BTW, I wasn't oblivious to the potential problem here but given my room/setup and the way the XLR connector wants to "sit" when correctly rotated and seated into the amp receptical it is difficult to avoid this result). So, this morning I moved the power cables around as much as possible to get them away from the IC in question and things improved--somewhat (I'm still not happy). Options? I could stay with balanced IC's but go with a cable with better shielding OR go with a pair of single ended IC's which not only move the cable away from the power cables (slightly) but also allow rotation which should give me (slightly) more wiggle room OR move the rack away from the wall a few inches to gain more leeway OR a combination of the above OR one of your ideas which I have not yet thought of. Thoughts? Many thanks as always.
dodgealum OP
1,398 posts
 
Sorry, Al, I forgot to include answers to 2 and 3 in my reply. 2) Flipping the ground switch introduced an additional hum so I moved it back to the original position. 3)Muting the preamp eliminated the hissing noise. Let me know if this alters your suggestion for a cure and thanks.
dodgealum OP
1,398 posts
 
Guys:

I may have been unclear and so driven the discussion off the rails. Almarg: your synopsis "a" is not correct: amp on + preamp off = noise. Again, none of the other components make the hissing noise alone or together. Just the amp when on alone or when on and the preamp is unmuted. I moved the cables as best I could away from the power cords and the noise is significantly diminished. I think this is the culprit and the sound will likely disappear if I can find a way to get the ICs between amp and preamp completely away from power cords.
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