Matt, These are functionally identical in this application. We've used both interchangeably for years. 73, Wayne N6KR On Jun 4, 2005, at 7:48 PM, Matt Osborn wrote: > I'm assembling my new K2 (#4978) control board and have found a > substitute part for U1. Instead of the NE602 or the SA602, my kit has > the SA612.... --- http://www.elecraft.com