DAC drops out when Furnace starts or stops. HELP


Every time my furnace or water heater (gas, power vented) kicks on or off my DAC drops out momentarily. My audio system, furnace and water heater are all on separate dedicated ac lines. My AC panel was updated to a 200 amp service some years back.
I checked all connections from the panel to each device and internally checked all electrical connections in the furnace and water heater, verifying proper hot, neutral and ground.
I checked and tightened all wires in the service entrance panel.
Has this happened to anyone else? If so what did you do to correct it?
Any help will be appreciated.
jadedavid
I agree with Al, that's exactly what I was thinking.
If you are familiar with electrical wiring, it should be an easy task.
What are you using for a digital cable? Length?

Try a different digital cable.

Make sure it is at least a 1.5 meter long.
.
good suggestions. Thanks. I will look into it tonight and report back with results.
OK, so I started by changing the digital cable (it was the easiest). I had been using an Audio Envy cable that I really like. Had it about one month. After inserting it into the system I had an occasional drop out but didn't think a lot about it. However as the cold nights came I started having more and more drop outs. Which lead me to tracking down the cause. Thus I discovered that it was the furnace and water heater making the disruption. Prior to the cold snap, it was only the turning on and off of the water heater that caused the drop out. But now with the furnace in the mix the drop out rate was increased signifigantally.
I replaced the AE cable with a Grover Huffman digital cable and last night experienced no drop outs.
The AE cable is only one meter while the GH cable is 1 1/2M.
Is it the length of the cable that could be the culprit or is it the design/construction differences?
Either way, thanks for the suggestions to get the gremlins out. I will also look into the service panel today to check the wiring as to which leg of the mains might be in common.