I have used the following circuit on a D104 to my K2: http://members.cox.net/n4jk/d104.htm Works great and you wire it for power through the mic connector. Mark W5EZY -- View this message in context: http://elecraft.365791.n2.nabble.com/D-104-preamp-tp5319528p5322031.html Sent from the Elecraft mailing list archive at Nabble.com.