carloc80 said:
now if I put 2 6l6 mesa tubes in the cornford(with bias at 35 ma) without rebiasing it,these 2 mesa tubes will work "hot","too hot",or cold or etc...???
Just because the tubes you had in the Cornford that read 35mv's or ma's,doesnt mean the next pair you put in will draw the same.Each pair of tubes will have their own current draw.You have to measure and adjust the bias every time you change tubes.With Mesa tubes they are tested and then sorted so when they sell you a pair of the same rating they will draw the same as the last pair you used.If you were to buy a batch of 20 tubes from Sovtek for instance and put them in a tester they will likely not all draw the same current.You would have to sort them and match the ones that are close in pairs or quads.This is why amps have adjustable bias pots.Contrary to what Mesa would like you to think,their amps are adjustable.Fixed bias does not mean non-adjustable,the term refers to a "fixed" amount of negative voltage applied to the control grid.Mesa just sets this in their amps and matches tubes that draw a safe,but cold current,to match their amps.Leading people to believe they have to use their tubes,and unless you know how to measure and adjust the bias,you should use them.A lot of tube suppliers have become aware of this marketing scheme and now sell you tubes that match the Mesa specs.