This is not a ground loop, or earth loop issue.
It does it when no instrument plugged in i.e Marshall ground the input.
It does not increase with volume, it stays constant regardless of amp settings.
I'm confident that it's not a faulty tube.
I know Marshall are not the most silent of amps, especially compared to my Messa Boogie Mk3 Combo or Fender Twin Reverb from the early 70's, but I was hoping it would be more silent than it is. For years I have ignored it as it was sort of fine at gigs, but now I don't gig much but use it at home and the odd bit of recording, it irritates me more and more now. :cuss
I'm not sure if this is a fault or just a design flaw, I have not a reference to compare it against to see if it is just mine or all of them.
Any suggestions as to what this might be, or how to fix/reduce the hum would be most welcome.
