Only use the JJ valves (see above) . Don’t bias them in the red of the dial, when setting up your amp plug in the speaker cable first, then the power cable so you accidentally switch on the amp with no load . Turn on amp power, tune bass, Set up pedals etc, then turn on standby in that order. After gig /rehearsal turn off amp first, then put away bass pedals etc . Move the head at the very end (I.e everything in reverse). That’s what I do anyway 🤷♂️. They’re very reliable If you treat them right . They don’t blow up like some class d amps I had !