Triple Rectifier tube bias switch

Hi,

I bought a Triple Rec second hand about 2 weeks ago. It is loaded with the Mesa Boogie 6L6-GC tubes, however, the bias switch on the back is set to 'EL34' and the red light indicating that also. The head runs just fine and it sounds awesome. Could it have been adjusted for 6l6's by a tech and the switch left in that position or should I flick it over to '6l6'?

Cheers!

Ed

Hi EB10,

It could have been, but that would be really weird to do so. No way to know without looking inside at the circuit. Likely the switch is in the wrong position by mistake, and although it might sound "awesome" for awhile, the tubes are cooking if the switch is in the wrong position. If you have a bias probe, it would be easy enough to check without disassembling the amp. I would advise getting this checked before you blow a tube and regret it. :idea:

Thanks shimmilou, I asked because a tube died earlier this morning, the switch being set wrongly would explain that and I agree it would be odd for it to be biased any another way.

Sorry to hear that, I hope that it is only a tube. If you have EL34s in and have the bias switch set for 6L6, no harm just a cold bias and maybe poor sound. With 6L6s in and the bias set for EL34, the 6L6s will be extremely hot and probably cause damage.

Yeah I'm hoping the same, though the head seemed to run fune up until the tube failed. I'm swapping it out this weekend and switching the bias over but for now I'll leave it unplugged.

Bias set to EL34 with 6L6's installed runs the tubes a bit hotter... Some guys say this is their "tonal secret". I don't think this will damage the tubes or the amp... probably the tubes life is burning faster. To be safe you can lower the internal voltage either by selecting Tube tracking (tube rectifier) or run the amp in Spongy-mode wile mismatching the bias.

Ran my triple like that for an long time before doing the bias mod. For mesa spec tubes it biases perfect if using rectifier tubes...way to hot using diodes, though.

R_ADKINS80 said:

Ran my triple like that for an long time before doing the bias mod. For mesa spec tubes it biases perfect if using rectifier tubes...way to hot using diodes, though.

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I had a friend, triple rec owner, who is technically challenged, always ran in diode mode, had 6L6's in the amp, and, he inadvertently got the bias switch into the EL34 mode. He blew his fuse at a live gig and he did not have a spare fuse. The bassist, who is a tech wiz, figured he would simply wire wrap the blown fuse with some copper wire. The rest is epic failure history, live and on stage. "What's that smell?"

Never trust a bassist with your guitar gear... with their fat strings :evil: