George,
I honestly don't think the problem is with my K2600. If you go to the thread mentioned above, you'll see that a number of other (knowledgeable) people have heard the same thing. That fact that I do not hear it with any other programs except some piano programs also supports the notion that it is in the programs, not the gear. One of the guys there who is very knowledgeable at programming the K2600 made a modification (which he describes in detail in that thread) to Program 1 which reduces most of the buzz problem.

He also helped me off-line repair a Sweetwater Grand Piano program which had the same problem.

So, I think it is something that most people apparently don't find objectionable enough to do anything about. But, I think it is there. Since you have worked so much with the K2600, I am surprised that you haven't at least noticed it sometimes. "Buzz" may be a bad description. It is a harmonic that is almost a high frequency hum, that has you opening you mouth to clear your ears.

Anyway, thanks for the reply. After you look through that thread, if you still think I am screwed up, please let me know!!
Thanks,
Mike