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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
mental
1,029 posts
 
Before I say bad amp you need to try another circuit to rule out some type of ground fault noise. Hum on an amp that's been isolated down to just speaker connections tells me amp needs serviced but do make sure you have a clean circuit providing power to the amp before making that call.

At the very least I'd grab a number 12AWG extension cord look for different circuits.

There is a difference between his and hum, yes? LOL
mental
1,029 posts
 
@ Grannyring...your post caught my eye. Thinking the same. I see you also brought that to his attention up above.
lak's avatar
Ag insider logo xs@2x
lak
3,516 posts
 
Here's another thought that happened to me several years ago that I almost forgot about. I had a similar problem and the cause was a loose ground wire in the main circuit panel.
Although it looked like all the ground wires were sercure, I traced the wiring for the outlet and where the ground wire was connected in the panel. Everything looked good but sure enough the group of ground wires needed to be repositioned and the screw bolt retightened. The hum stopped. You might want to check that out if the amp tests goos at another location.
mwsl OP
26 posts
 
LAK - very interesting possibility. There's been lots of work in our panel over the years. i will try to check it out!
grannyring's avatar
grannyring
4,637 posts
 
Put another amp in and if quiet......power supply caps :)
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