Very strange indeed. I would go back and hook up each C-J component to each Bryston component again, and run them that way for a few days to see if the problem eventually crops up when the PV-5 and MV-50 are isolated from one another or not. (About AP's suggestion, I am pretty sure C-J is using Sovtek/E-H EL-34's; I take it that your output tubes are biasing properly?) If the problem never shows up when using these in combination with the SS components, but comes back as soon as you reconnect the C-J's, then you might want to try subbing out some spare tubes (if you have them) in the preamp's line stage sockets (the fact that the problem apppears in both channels makes it unlikely that this a faulty tube problem in the amp).
My Tubed Amps Entered "Twilight Zone"
Last week, My Conrad-Johnson tubed PV5 preamp and MV50 power amp started to emit a loud hissing sound through both speakers about 10 seconds after turning on. So loud, that I had to shut them down. I checked all the tubes and they all were lighting up. MV50 was re-tubed 2 months ago by CJ. I then hooked up the PV5 to my Bryston 3B-ST power amp. The sound was perfect, with no hiss at all. I then tried my Bryston B-60P integrated as a preamp with the CJ MV50 power amp. No hiss and the sound was great. I re-connected the PV5 to the MV50 and used different interconnects and the loud hiss returned. Very frustrating experience. I called CJ service department. Knut suggested that one or both power supplies of the PV5 or MV50 needs replaced. If the power supplies are bad, why do they play well with the Bryston SS amps? The loud hissing occours only when the CJ equipment is used together? Any suggestions of what is going on here? Thanks, Pete.