I had these EH EL 34's for 8 months and starting to get that hum like the last set did so I replaced them. This hum wasn't as bad so I was trying to more mileage out of them. Today it seemed like it didn't have much sustain so I looked at the back of the amp and seen one red plating I don't have a meter yet should I recheck the bias maybe that will solve it or just order a new set of Rubys which I going to get next? Thanks!
I wouldn't buy ruby tubes...sorry. But...reverse the tubes in the sockets....and test again. Now check to see that the problem IS(?) the tube (the same tube will red plate?) OR the problem IS(?) the socket....now the other tube red plates instead? Make sure it's the tube and not the socket first.
I had it happen with a new pair of Chinese power tubes in my DSL 50. I had the amp dimed and was playing behind the head. One tube looked like it was full of lava and was about to burst. It blew a fuse and then cooled down.
Your dsl40c will have a hum..Couldn't get rid of it on my clean channel. Poorly made Vietnamese amp..sorry but it's the truth..had the same problems with mine. Shipped it.
It was the power tubes before and now that hummed, thinking the amps vibrations causes some issues down the line. I replaced on of my older tubes and biased it up last night
