running Marshalls cathode biased

[kg]

to go along with what john said, if your plate input power (ie, plate voltage * plate current) HASN'T changed then you are not stressing the PT any differently. you will get less power output (because Vak is decreased in the output stage), but the amp is essentially running just as it was before. as john says he likes to run them hotter, but you don't NEED to run them that way.