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
I just cured a spkr hum problem yesterday! Directly thx to A'gon! A little background 1st. A few years ago I moved from a house to an apt. I set up my system exactly as I did in the house, fired it up and there was a low-level hum/buzz that wasn't present at the house (where it was dead silent). Checked all my connections and plugs and the sound persisted. I've read that apts. often have problems due to 'sharing' (for lack of a better term) the electricity with all the other tenants. I was even using a power conditioner, that I assumed would be an asset (I'm sure some of you are guessing where this is going!;). Cut to a recent thread about power conditioners here on A'gon. Whether or not they hurt or help sonics. I figured I'd check it out just for giggles, I've had my amp plugged into my PC for 7-8 years! Guess what? Not only did I hear an immediate improvement, but the buzz/hum is 100% GONE!! Is this hobby the gift that keeps on giving or what!?;)
Disconnect the interconnects from the amp and power it up, no hum I bet. Reconnect each component's interconnects one at a time, power it up, shut down and go to the next component until you find the hum....voila.

I never run video into my system via interconnects and never on the same circuit. I prefer toslink for that application. PC into my system I prefer wireless.
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
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