In a message dated 7/25/2006 5:17:20 P.M. Central Daylight Time, rayfri at highstream.net writes: I also found an SB 604 ... listed as a Balanced Line Tuner My SB-604 is a speaker... I thought they all were. There IS room in there for a power supply, I suppose a tuner would fit instead ;-) 73, Don - K4BEV