Anyone Know What Bias RKIIs Are Set At?

[CudBucket]

I was hoping someone knew how Mesa sets the RKII's bias out of the factory. Just wondering about maybe having an adjustable bias pot installed in mine.

 

[Boogiebabies]

-53 on the 6L6's and -38 on the EL34's. There is a trim pot in there though as well as the RK I, II and II v.2. I have not messed with it, but I beleive it is for the EL-34's.

 

[CudBucket]

Thanks BB. Is that considered a cold setting?

 

[Boogiebabies]

It depends on what natural plate current the tubes draw from it.
This is why Mesa color codes their tubes. Gray and White are hotter than Yellow and Red so if you have Yellow or Red 6L6's they will be cold at -53. -39 on an EL-34 should be nice and warm on most of the Mesa color codes, but may be too high on Gray or White. I'll have to break out the Bias Meter and see what they draw. I am thinking of going with KT-66HP's in the RK II v.2. The amp came with Red's and seems to lack some high end, so I switched to yellow and will test them tonight. IMO, Mesa's run much clearer when they are biased cooler. Once you get to 75% MPD, they seem like real mush to me. I never run them above 60%. I also just came into some 1950's Sylvania 5U4G's. It would be cool to see how they sound in the DR or RK.

 

[CudBucket]

Thanks again for the info, BB.