Yes it can be done, I have four 6L6's that can be run in the EL34 posistion to bring the bias up to the right amount.
Basicaly how it is done, is the 6L6's are very cool running, meaning if you were to put these 6L6's in the 6L6 Mode they woud probaly run a bias of about 5 to 10 Ma's (very cold bias). Since they are so cool they can be run in the EL34 Posistion which brings the bias up to about 35Ma's which is where the bias should be anyway for 6L6's.
Now with a intgrated quad, they are going to send you very cool 6L6's and then EL34's that are normal so this way all four tubes will be pulling the same bias of about 35 to 45 Ma's.
Will this hurt your head, no, because normaly if you had all four EL34's that is what it would be running anyway, you are just tricking your head into thinking it has four EL34's. So what is the catch, well since you are running the 6L6's at the normal bias they will wear out faster then if you had it in the 6L6 Mode, is this bad no.
Have you ever noticed mesa tubes last forever, well it has nothing to do with the fact that they have better tubes. It has to do with the fact that mesa sets there bias cold on there amps, so you are really not wearing the tubes that fast. Take a Marshall amp that is biased right and you will have to replace the tubes alot sooner then you would in a mesa.
Yeah you are probaly thinking, well why do i want it to run at the right bias if i have to replace tubes sooner, well because the amp sounds alot better when running at the right bias, tighter and more power tube distortion. Mesa builds most of there amps around Pre-amp distortion, not a bad thing, but if you are like me sometimes you might want the power tube distortion more, it is warmer and just has a different feel.
