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Speaker hum problem - need help

I've searched the forums and have seen past posts for this topic, however, I've yet to find an answer that fits my situation.

First, here's my equipment:
Coda CSib integrated amp
Ayre QB-9 DSD DAC
Auraliti PK-90 USB server
Dynaudio Focus 380 speakers
Audience Au-24 speaker cables
Cardas Clear XLR interconnects
Cardas Clear & Grover Huffman power cords
Wireworld Platinum Starlight USB

Here's the problem:

With only the amp plugged into power and the speakers connected, I get a 38 db invariant hum coming out of the speakers. The hum does not change no matter what the volume is on the amp. The hum does not change regardless of whether I have the amp plugged into the: wall, a power strip, or a power conditioner. The hum does not change regardless of power cord connected to it. The hum does not change when I plug in the remainder of components and cords into my system.....it is invariant.

I have tried to "lift the ground" with a 3/2 cheater plug, but this had no impact. I sent the amp back to the factory to be checked out and slightly upgraded; they could not reproduce the hum at the factory. A previous amp (tube) produced the same issue, however, with the tube amp, the hum got worse as the volume was raised.

I love the overall sound of this system, but this hum is definitely getting in the way of my enjoyment. Any thoughts out there about what is causing this problem and how to correct this issue?

Many thanks,

Matt
mwsl
wescoman
113 posts
 
Just a thought - make sure you don't have any halogen lights with variable dimmers turned on while using your equipment. That definitely affects my equipment.
mwsl OP
52 posts
 
Sounds like many of you are concerned about the "health" of my outlets. The house was brand new in 1990....meaning all new (to code) electrical at that time. I did install both audiophile outlets myself....and know they were done correctly. I do have a halogen cable lighting system installed in the living room, and the transformers live in coves at the top of the walls where the suspect outlets are located. I do, however, have the lighting system completely off when I play music, as I am aware of the noise that the lights add to the system. Is there any chance that the presence of the transformers 8 feet above the outlets might be a cause of this issue....even if the lighting system is turned off? I will start with the extension cord suggestion, and go from there. Thanks to all of you for your suggestions. I'll report back.
lak's avatar
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lak
4,529 posts
 
Very interesting.
Thank you for your willingness to report your findings back to the forum.
I wish everyone would have such good follow through.
zd542
5,339 posts
 
You said that you sent the amp back to the factory and they couldn't find anything wrong with it. Assuming the amp is OK, I would try 2 things. The first would be to connect a different pair of speakers just to rule them out as the problem. If the hum is still there, try the amp in a different location. Maybe in a friends system. That will tell you a lot about what is causing the hum.

One thing you really need to do before making any decisions or spend money is to hear the amp working without the hum. If not, you can't rule it out. The thing you say about the AC being the problem that gives me pause is that you tried different power products and there was no change whatsoever. If your AC is at fault, I would expect you to hear something if you tried different solutions, like a line conditioner. Even if it didn't fix the problem, I would expect to hear some difference; whether it be better, different or worse. I could be wrong, of course, and maybe the AC is the problem, but I would need to hear the amp working properly before I tried fixing anything else.
plasmatech
77 posts
 
Try another amp/preamp in your house. It may have really crappy AC outlets with wires just plugged in and old ones can make intermittent contact. Wiggle the plug in the wall and see if the hum changes. Usually a hum equals a ground loop. This is a mystery. Take your Coda to a friends house. If it (coda)works there, and something different in your house doesn't work, your wiring/outlets is suspect. If the Coda hums at a friends, send it to Coda again.
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