Mark IV Power Tube Location and Rating?

Just recieved my used, new to me Mark IV short head. Looking at it and checking it out I noticed that the stock 6L6's have different markings on them. Not painted on the tube but on a sticker at the base, I assume this is Boogie's testing and rating. 2 tubes are 37 grey and the other 2 are 27 red. However the 2 grey ones are in the right sockets, as I look in the back and the red are in the left. Knowing if you put in EL34s you use the outside sockets is this correct? Also what do the numbers and ratings mean? I'm a rock and some metal player so what would I want where?

put the pairs in the outer sockets and inner sockets (NOT side by side)

Try 'em both ways, and see what you prefer...

Great, That's what I thought. What do the Mesa numbers mean? I know that others have suggested that the different colors give more headroom, distort sooner etc.. What's the deal.

mtnb1kr said:

Great, That's what I thought. What do the Mesa numbers mean? I know that others have suggested that the different colors give more headroom, distort sooner etc.. What's the deal.

Click to expand...

Better ask Mesa. They could be "milliamps", as in a bias rating. It could be some dumb scale they made up.

Best to arrange them in pairs, an inner pair and an outer pair.


As far as that "distort sooner" aspect, forget about it. Do you know HOW LOUD the amp will be near clipping? Even just using the inner pair in Triode-Class A mode will be deafening near clipping. IMHO, attempting to get poweramp distortion from a 6L6 or EL34 amp isn't worth the effort, although some swear by their power attenuators.

That's why Boogie made MASTER VOLUME amps in the first place. So people wouldn't need fuzzboxes, or attempt to get poweramp distortion from a 100 watt Marshall. It really revolutionized the amp business, although Boogie wasn't technically the first with a master volume.