In case anyone else is interested in building a mixer, you might want to know that there are a great number of inexpensive 10K, dual element audio slide pots available on ebay. Expiring tonight, the auction no. is 1328702387. Unless somebody pops up out of the blue to buy them all, they will probably be available later, too. The fellow selling them is Hank Landsberg (Henryeng@aol.com). They are of Taiwanese origin and have carbon elements (not really what we want), but they are 4 in. travel, and very inexpensive. I don't have any connection with Henry, but I thought some of y'all might be interested.