Do you have another source you can try? Most likely culprit is a bad tube but it's possible you lost a channel in your cartridge. At least with a cd player you can rule that in or out pretty quickly.
What might cause loss of sound in one speaker?
Today I put on a record and there was no music coming out of my left speaker, only a static hiss sound. When I mute the line stage the hissing goes away. I have a Aesthetix Rhea phono stage, a Calypso line stage, and an Ayre V5-xe amp. I have checked all of the connections and everything seems to be connected properly. Additionally, I gave the tubes in each unit a quick visual exam, but didn't see anything that seemed unusual. However, I know nothing about tubes and am not sure if there would be a visual cue if something was awry. Can anyone give me some suggestions of what might have gone wrong, how to confirm it, and the best solution for that problem.