My new Mesa Boogie Mark III Red Stripe

[AlexRaymond207]

Hi everyone! I just picked up a mark III a few days ago, and i am loving it!! That being said, i have a few concerns and questions. I noticed that the outer pair of power tubes are a different brand then the mesa inner tubes. Now the amp has a switch on the back 60W 100W. When i run it in 60W mode is it still using all 4 power tubes? Also the inner pair glow very pale and the outer pair are as bright as can be... Is this an issue? It sounds fine to me, just wondering if i should change them out... Also in reading the manual they said i don't need to fiddle with bias when changing tubes as long as they are mesa tubes, but since the outer pair are different should i have this done? Thanks for you time!

[GibsonLover]

I have a MKIIB, but I think they are wired the same. The 60/100W switch disconnects the cathodes of the the two inside tubes in the 60W position, so there is no B+ current flowing. The heaters are still on though. Sounds like everything is working as it should.
I wouldn't worry too much about the bias. Mesa wants you to buy THEIR tubes, because they are screened to run in a certain range. I've never had a problem with anything I pop in mine. Some people add a bias pot, but that's really up to you. I think if you don't like the sound, try a different set. For instance, play for a while with the 60W switch, then swap the inside two with the outside two (power down first). Even though they are different tubes and you may hear a difference, it's not a ground moving difference. If it is, you have just identified a pair that is significantly stronger or weaker by comparision. I've never worried about it.

[AlexRaymond207]

Thanks for the tips! I will try it out

[AlexRaymond207]

So i tried switching the inner pair and out pair with eachother and go a really strange buzzing sound. So i switched them back and go no such sound... Im a little confused as to why though. I did it twice with the same result, made sure they were being put in the right way and everything. Its not a big deal because its fine how i have it set up, just would like to know why its happening. Thanks!

[Marcus71]

The outer tubes on a Mark III are supposed to be EL-34's and the inner ones are 6L6's.

I just bought an early Mark III and found that out a couple of days later when I downloaded the user's manual from Mesa's website.

Note: this is only true if your amp is a Simul-class. If it's not, then all 4 should be 6L6's.

[acorkos]

So i tried switching the inner pair and out pair with eachother and go a really strange buzzing sound. So i switched them back and go no such sound...

buzzing in 60w or 100w (or both)?