i have a fender deluxe 5e3 tweed amp that has not a hiss, not a hum or a Shhhh sound, but a BUZZ whether the guitar is plugged in or not and whether the volume is on or not. when i turn up the volume for the instrument channel the buzz gets louder and becomes increasingly louder the more i increase the volume and with that volume knob turned up all the way the buzz changes to a high pitched screech. when i try the same thing on the mic channel there is no change in the buzz. when i play my guitar through the amp with the volume on and through either channel the strings sound distorted. before this happened i had just replaced all my tubes with brand new JJ's and it was playing beautifully.