The quirky hum in my SA-2

[tygr]

I get a low hum when using 8ohm speakers and the 8ohm tap on the OT.When I use 4ohm speakers and the 4ohm tap, no hum.

Any clues from the tube gear gurus?

 

[dcgillespie]

My first guess would be that the 8 ohm speakers are more sensitive, allowing you to hear the hum, while the 4 ohm speakers are less sensitive, so you don't hear it. Even if this is not the problem, the efficiency of the speakers involved need to be known to either eliminate or account for any variable that exists between them.

Dave

 

[tygr]

Thanks Dave, actually I think you have hit the nail squarely on the head.