My Peavey TNT amp is making a loud buzzing (not hissing) sound when my bass is plugged in and the volume is up. EQ and bass settings have been manipulted to get rid of the buzz, but to no avail. What could be happening. We have used several basses and several cords and several outlets. What's up?
Could be the wiring of the outlet or noise from the lights in the room etc. Try a different plug in the room first....
if the amp is quiet without an instrument being plugged in, it's instrument or environment. If the problem occurs with mulitple cords/instruments/outlets but not with the amp on and unplugged (instrument) that leaves only environmental issues as the cause. one word of advice, different outlets means a different CIRCUIT. Not a different outlet in the same room on the same circuit. Good luck....
The power supplies in these amps aren't very well shielded. Try checking that your guitar is placed well away from the amplifier. I used to get the same thing with the Peavey I had years ago whenever my bass (Passive Jazz) was within two feet of the amp.