Bugera 333xl 2x12 combo - breakthrough hiss on crunch n lead channels

[jmp220478]

new to forum - out of warranty Bugera 333xl combo

Unit has developed a hissing noise which doesnt happen on clean channel - it can be played over but as soon as i stop playing its quite evident - i can reduce this by turning up the overall master volume and reducing the channel volumes but wasnt there until recently ??

ps - i have previously had the transformer hardwired after a burnt out on the molex(?) plug ...

cheers

[52 Bill]

Perhaps a bad preamp tube. What have you tried so far?