A mystery for you tech gurus out there

Is it possible that someone needs to brush up on their Dale Carnegie? The question does assume that the person wants to be liked by others. Anyway, here's a brief synopsis of some of Mr. Carnegie's most core techniques.

Fundamental Techniques in Handling People --
Don't criticize, condemn, or complain. Give honest and sincere appreciation. Arouse in the other person an eager want. Never show others that you are not interested in what they have to say.

Twelve Ways to Win People to Your Way of Thinking --
The only way to get the best of an argument is to avoid it. Show respect for the other person's opinions. Never say "You're Wrong." If you're wrong, admit it quickly and emphatically. Begin in a friendly way. Start with questions to which the other person will answer yes. Let the other person do a great deal of the talking. Let the other person feel the idea is his or hers. Try honestly to see things from the other person's point of view. Be sympathetic with the other person's ideas and desires. Appeal to the nobler motives. Dramatize your ideas. Throw down a challenge.

Regarding the OP, it could be some outside electrical interference being picked up by a interconnect/cable on the left channel. Try repositioning.

Sandstone ... this is what qued me

-Denon 1913-AVR receiver

It's a HT receiver not 2 channel receiver and requires balancing of input signal to all channels including sub for balanced response

Turn one channel’s input up a little to much in relation to the others and it will clip before the others

OP descript sounded like clipping to me

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Snwbrdrcol, have you switched interconnects/cables around?

The chickens always do come home to roost, don't they.

I must appreciate Onhwy61's great post. That's my dad's favorite book.