Lampes de puissance Mesa/Boogie 6L6 GC STR

Citation : Mesa scale Groove Tubes scale
Red 4
Yellow 4
Green 5
Gray 5
Blue 6
White 6

source : http://www.guitaramplifierblueprinting.com/Rating.html

Citation : TIP OF THE WEEK

This was an article on tube manufacturers and how the "Groove Tubes" 1-10 scale could be used for tubes that were desired for a Mesa Boogie amp which has a fixed bias.

Tech Tip 021402 - Groove Tubes vs. Mesa Boogie Tubes

In the case of Groove Tubes, they use a rating scale of 1-10. Mesa Boogie uses a color code system. Here is the cross reference to use the same "grade" of tube if you switch from one vendor to the other:

Mesa Scale crossed to Groove Tubes scale

Red 4

Yellow 4

Green 5

Gray 5

Blue 6

White 6

The reason for Mesa's narrow range, is that their amplifiers do not have an adjustable bias. This way if you have one of their amps, you can use any of their tubes safely. For amplifiers without an adjustable bias, if you want more headroom and/or power as an example ... and you amp had a #5 or Mesa "Green" tube in it .... and had an idle dissapation of about 50%, you would just go to a "White", "Blue" or a Groove Tubes #6. You will see your idle dissapation go up to maybe 55%. This is a way to fine tune your amp.