DAC drops out when Furnace starts or stops. HELP

Thanks to all for the suggestions and info. After listening again tonight I have had no drop outs with the 2nd digital cable in place.
However I think "Almarg" has hit on the root cause.
I have been constantly fighting a ground loop hum that I cannot cure.
I have tried cheater plugs on some/all pieces of equipment, plugging all the audio gear into one strip, isolation transformers ETC ETC.
I have come to the limits of my knowledge of finding the source of the imbalance.
Thanks for the ground/neutral info from "Cdrc".
I think it"s time to call in an electrician. Hopefully I can find one who understands this type of problem.

I think it"s time to call in an electrician. Hopefully I can find one who understands this type of problem.

Your average electrician will not solve a ground loop problem.

Here is a white paper for you to read.

I have tried cheater plugs on some/all pieces of equipment, plugging all the audio gear into one strip, isolation transformers ETC ETC.

What equipment in your system uses the AC power mains safety equipment ground? (Check all audio equipment with an IEC power connector for the safety equipment ground pin/blade. If only 2 blades the equipment ground is not used on the equipment.)

Are you sure you are hearing a hum or could it be a low level buzz?

It would help if you listed your equipment, ICs, speaker cables, and any after market power cords you are using.

By chance do you have a TV with CATV or a Dish connected to the system?
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FYI, I have found no correlation between length of USB cable (1m vs. 1.5m) and performance across brands. You are not assured superior quality/performance from a supposedly ideal 1.5m USB versus another brand 1m. It is also relatively easy to find a 2m USB which will outperform any given 1m or 1.5m alternate brand.

I have a few times found that 1m sounded better of the same brand than 1.5. So, you can say I'm not a believer in the idea that 1.5 is somehow magical for sound quality of USB.

Douglas_schroeder,

I use a 2 meter digital coax cable myself. I don't think anyone here said a 1.5M was the magic length.

I think Al, (Almarg), and Kijanki offered a more technical reasoning why the digital cable made the difference and the fact that Jadedavid solved his dropout problem using a different digital cable tells others that are experiencing dropouts caused by the switching on or off of an AC mains load/s it might save them a lot of time to just change out the digital cable instead of spending maybe hours looking for an AC mains problem that may not be their problem at all. It might just be the digital cable. In the end that's all that matters.
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Jea48, Yes, I understand the flow of the conversation.

I was simply following up on Al's side comment about cable length. i.e. If someone has a choice between a 1.5m and 2m USB if possible one should try them, as opposed to thinking that the theorized ideal length cable would automatically be superior. I do, however, favor a shorter USB when I can obtain it.

I also have seen one or two instances in which a particular USB cable worked with some gear and not others. So, it is wise when experiencing a snafu with digital to consider that the USB cable may be incompatible with a particular component.