CJ PV-10aL Problem

This afternoon, I fired up my system and lo and behold, I notice a certain hiss and crackle from my left speaker. Check connections, no issues. Try different amp, no issues there. Change pre-amps, hiss and crackle goes away.

I just got the CJ and am I to guess that it is the tubes? What else would cause the hiss/crackle?

I am now using a Rotel RC-955 pre and umm, I think I like the tube sound better.

Thanks,
E