Top 5 in no particular order: Henry Kloss, William Z Johnson, Peter Walker, Nelson Pass, Saul Marantz/Sid Smith. Kloss was well known in his day to be a genius. His inventions had wide applications, even outside audio. Bill Johnson is most responsible for the renaissance of tube gear starting in the early 70s. Peter Walker belongs just because of the Quad 57 and 63. Nelson Pass is possibly the smartest of the many excellent designers of solid state gear. (Honorable mention to John Curl, Dick Sequerra, et al.) Saul Marantz was Saul Marantz. Some of the guys that have been mentioned are indeed associated with great products, but not all of them were truly great innovators and designers. There are a lot of young very bright guys, but they have not yet had the major impact of those listed above and may never do so, since we are now seeing the decline of high end, 2-channel audio as an art form. Vilchur belongs in the above list too, but I left him out in favor of Kloss. Hey, and my personal favorite, Julius Futterman, who designed, patented, and marketed the first OTL amplifiers and was a wonderful human being.