One channel or two? What about the speakers, have you switched them? Do you have more than one source component? You probably have already thought of all of these, but your posting doesnt mention them, so just in case....good luck.
Why is my amp distorting?
I have a vintage McIntosh 240 that recently started distorting music. I've changed tubes, preamps, wires, line conditioners; no help. I've also taken it to a repair shop where it was scoped and given a clean bill of health. I've used this amp for about 4 years with no problems until now. And I know it's not some audiophile affliction because my wife also notices the strange sounds. I'm at a loss to know what to do next. Any suggestions as to the problem?