Popping from right channel of Musical Fidelkw500

I am getting a popping/crackling sound from the right channel connection of a Musical Fidelity KW500. It exhibits this behavior with no source connected. The sound gets louder as the volume is turned up. This behavior is also noticed if I connect the preamp outs to another amp and connect speakers to the other amp. I have tried different speakers and have the same result. Any thoughts on what the problem could be? Thanks
Probably a bad tube in the right channel. I would probably look into having it replaced. You might want to contact Signal Path in North Carolina on this.
I had the same problem when mine was just a few months old. Had to send it back to MF - they said it was NOT the valve as i had first thought BUT did not give a satisfactory answer to what the fault was. It did sound just like the valve to me, but i am no expert
I had the same popping problem in the right channel. Sent it to Signal Path and it WAS a bad tube. It's funny but all the reviews and MF literature say a tube has never"failed in the field." What is that about? Their tech was non responsive when I enquired by letter about this. But the tube was replaced and unit is fine
can you swap the tubes around to see if the popping noise changes channels?