I have a SLI-80 and its dead quiet. To clarify, is the hum coming from the speakers or from the Cary itself? If through the speakers, does the hum come through both speakers or just one? If its just from one side it could be a bad tube. To test you could swap the tubes from one side to the other to see if the hum changes sides. If so, then swap out one tube at a time on the side with the hum until it disappears.
Since the hum is immediate upon firing up the amp, it doesn't really sound like a tube to me, but you may want to try the above just to start ruling things out. As recommended, give Cary a call - they have great customer service in my experience.
Since the hum is immediate upon firing up the amp, it doesn't really sound like a tube to me, but you may want to try the above just to start ruling things out. As recommended, give Cary a call - they have great customer service in my experience.