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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
mwsl OP
26 posts
 
Al - there is no hum coming from the amp itself.

Mental - I have already tried the experiment of disconnecting everything from the amp aside from speakers cables and the power cord. I get the hum just with that minimal set of "items" plugged in.

Matt
grannyring's avatar
grannyring
4,637 posts
 
Power supply caps..........I persist.
jea48
2,944 posts
 
Mwsl,

Do you have an AM/FM radio you could plug into the same mains power receptacle as the Coda amp? If so set the tuner to an AM station and listen for the hum/buzz.

If the radio sounds ok then I would think the problem is not AC mains power related but rather a problem with the Coda amp.
Jim
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.
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