Hi dbert -
Thanks for the comments and follow up. Well, a few to add, process of elimination and avoiding the grimbly. I received a response from Klipsch today re. volume issues. Their response to my request for service info. etc: "purchase a new dock" for $57. Provided they suggests takes care of the problem, then for the moment we can presume the problem is in the cable to the dock.
(And reading your comments, I'd say, toss the IC into the suspect pool. Often in my service days, we'd see a bad batch of chips come down the pike that would mess a lot of things up. However, high power, high heat, high demand ICs fail 100:1 to simple, low-power ICs.)
It still may be noise in the power, grounds or from the volume switch, or pot. (I'll look it up eventually). That's to say, because the circuit is essentially idle until input is sent to it, low/noisy power, and/or faulty grounds may only have an effect once the chip begins to function. This could be determined easily with a schematic and oscilloscope -- which I have neither in front of me at the moment.
As a former service center owner, I would routinely contact companies, such as Klipsch, and order a schematic. These days with the Web, more of that's done online with PDF-types of diagrams. I haven't seen any out there as of yet.
Perhaps if someone knows of a service center who has the diagram or would be willing to order one, they could let someone know.
If anyone is reading this at Klipsch, no bad feelings, I hope. I'd figure for most, it is easier to spend $57 to buy a replacement than spending an afternoon taking apart a dock and trying the do-it-yourself routine. I think, however, 1.) if people felt confident the replacement dock wouldn't fail prematurely like the original ones did, they'd just order it and go on their merry way, and 2.) for those of us who would prefer to mess with our own stuff, we'll find the cause/solution eventually -- with or without your support -- and then we'll blab it to others.
So, a little honesty and help could be in order here. But what do I know, I only handle corporate communications for a Fortune 10 consumer products company.
TD