Hissing sound from right speaker

I fired up the system last night and began listening to a LP that sounded like it had horrible surface noise. Upon investigation, it was not the LP, but a loud hissing noise coming from the preamp. When I muted the preamp, the sound went away. By changing input selector (LP, CD, etc.) there was no change. It is a Klyne pre plugged into a PS Audio 300 power supply.

Any thoughts on how to trouble shoot this issue?
Sounds like you may need professional help.
Swap preamps output cables left to right and see if the noise changes with it. If yes, you narrowed the problem to just the preamp. Try tube replacement to further narrow the problem to the tubes (or eliminate them from the list).
Think you need troubleshooting flow chart. It will help to narrow down to piece of equipment where problem lies. Had a similar problem recently. Muting pre-amp seemed to elimiate problem, but with use of http://www.avahifi.com/trblsht.htm I found out problem was bad power transitor in power amp. Wasn't expensive to repair. $90 including S&H. Good luck.

you may be losing a tube , move them from right to left and see if the hiss follows.
There are no tubes in the system are there?
likely the power snakes pc's.
Klyne preamps are solid state!! I really think he does not have a bad tube.

Could be a bad resistor, which is why I would seek professional help. Call Klyne first.

Thanks for yoru responses. After the problem occured, I turned everything off overnight. Last night I fired it back up and had could not replicate the problem, even after 2 hours of steady listening. This probably lends credence to an intermittent tube issue in my amps (Manley Neo Classic's). I appreciate the input and will troubleshoot accordingly should the problem rear it's ugly head.