Groove Tube Number Scale vs. Mesa Color Coding Scale

[doctorgonzo69]

I was always sort of fuzzy on what exactly makes a tube compatible with a fixed bias amp like a Mesa Boogie. I'm still fuzzy on specifically what range of value or characterstic of a tube makes it suitable for a Boogie, but a recent correspondence with a representative from Groove Tubes does shed plenty of light upon which Groove Tubes might work in your beloved Mesa Boogie amp.

Me:
"Hi,
I have a Mark IIC and a Dual Rectifier that I'd like to re-tube, and I'm pretty impressed by your 6L6GE tube, and I want to try it, however I'm a bit unsure about how to select a non-Mesa labeled tube that might work best within the limitations imposed by my amps' fixed bias circuitry. What value does Mesa "look at" when testing a power tube to insure it's compatibility with its own amps and thus what should I look for?
Thanks for your assistance.
Sincerely,
-lus casarez"

reply by Myles Rose, Groove Tubes Dude:

"On rating numbers:

Basically, a #1 will distort sooner, and a #10 later. If, for example,
with a mid range tube, say a #5, makes your amp start to break in the
output section at a volume setting on the amp of "4", then with a lower
number tube, like a #2, your amp would have a same sort of break into
output distortion at say a volume setting of "3". With a higher tube,
such as an #8, then you amp would stay clean to about perhaps "6" on
the volume.

High rating numbers are not more or less powerful, they just distort
later. These are preferred by heavy rocker that want maximum clean
output, as they get their distortion and tone from effects or pedals.
These are not as touch dynamic.

Low number tubes are very touch dynamic, and more suited for a
lot of folks, for smaller venues and recording.

Most folks prefer the 4-7 range tubes, as they are the closest in character
and touch to what the amplifier designer had in mind. They are also the most
versatile.

On scale conversions:

On Mesa Boogie amps there are six color codes.
All of them are in the GT 4-6 range. These amps
have a fixed bias to staying in this range is the
same as Mesa tubes.

Mesa vs Groove Tubes scale

Red = 4
Yellow =4
Green =5
Gray =5
Blue =6
White =6"

I don't know about you guys, but I'm breaking out my debt card, going to musician's friend, and hooking up with some GT 6L6GE's!

 

[Guitarzan]

So now everyone can see that the #4 GT's are your hotter tubes, You can pretty much cover the spectrum with GT. The 'S' suffix means they are JJ's, 'R1' means Svetlana, 'R2' is SED/Wing C, 'C' is Chinese/Shuguang.

I'm breaking out my debt card, going to musician's friend, and hooking up with some GT 6L6GE's

I have a quartet in my Rev. "C" Dual Rec. Great tube! Very Tight and musical, not as much bottom end as the JJ's but a worthy addition to any Mesa!

 

[MesaDCLP]

I've had GT rating questions as well and received this reply in context to my question:

"7 is about as high as you can go and even with a 7 in the output section I would check the bias." -Myles Rose

Two things to note though:

-With newer amps under warranty, anything but mesa voids it. But can they really tell if the tube drew too much power through the circuit? I think if the tube isn't bad, they would suspect something.
-Mesa tubes are matched closer to one another than GT. Might as well say the rating system is:

4 -Red
4.5 -Yellow
5 -Green
5.5 -Gray
6 -Blue
6.5 -White

Talk about fine tuning, within spec, and under warranty.

My amp is fixed bias, ...and so am I. 8)

 

[MaxBoogie]

Okay the Mesa tubes ALSO have "numbers" on them as well as the color code. I see mine are all matched for the color and number, but my different amps have different numbers. Does it mean anything significant?

 

[LSS Vic]

Guys.

I bought 4 GT6L6B Blue tubes over the weekend to re tube my 2 channel Dual Rectifier.

I bought the amp with MESA EL34's installed and thought that I needed the 6L6's to get a heavier sound.

I installed the new GT 6L6's, changed the bias setting to 6L6 (obviously) and powered up.

GRRRRR......so much fuzz!! The tubes sound too Fizzy for me? Is this how 6L6 tubes are supposed to sound?

Sould I try to get hold of MESA STR 440's? Or will I get the same sort of sound from them? :?

 

[Russ]

You should be looking at the hardness rating of a GT not the color.

You should be looking at the color rating of a Mesa not necessarily the number.

The different STR ratings by Mesa just differentiate the different models of tubes.

 

[Russ]

No, 6L6 shouldn't sound like that. I would check the hardness rating of your GTs or even take them back and swap them for another set of proper rating. To me it sounds like your hardness rating is too light. If I am not mistaken the GT blues are on the lighter side numberwise and distort sooner making for power tube distortion sooner. You want a higher number to let your preamp tubes do their job in a Recto. Clean headroom will make it feel like it is hitting you in the chest.

 

[Russ]

Also, I am not sure that a Recto can accept GT6L6B's anyway. I would try another higher hardness rating first then go with the GT6L6GE and be done with it. Make sure that you get a 5-6 hardness rating too.

 

[Cleekster]

No, 6L6 shouldn't sound like that. I would check the hardness rating of your GTs or even take them back and swap them for another set of proper rating. To me it sounds like your hardness rating is too light. If I am not mistaken the GT blues are on the lighter side numberwise and distort sooner making for power tube distortion sooner. You want a higher number to let your preamp tubes do their job in a Recto. Clean headroom will make it feel like it is hitting you in the chest.

Your assuming russ that he isn't like the rest of us that actually PREFER power tube overdrive. i have a recto and my mesa tubes are a "red" and i find that they don't distort soon enough for my tastes.i have used groove tubes in the past and found that a 4 is as high as i can stand.maybe i'm just old-school but Power Tube distortion is where it's at.

 

[Russ]

I am definitely of the old school mentality of power tube distortion but for his description it sounds like he wants headroom. You only can achieve headroom by getting tubes that distort later. Believe me I am all about having an amp that truly sounds driven. I would much rather have an amp that sounds pushed than have it all be front end. In the case of my Mark IV though I like it to have headroom. In the case of my Marshall JMP I love early break up. In the case of my 800 I like headroom most of the time. My JMP is still my favorite amp but you cannot use a hammer to turn a screw and it is hard to cut your steak with a spoon. In the case of my more modern playing I prefer headroom so that it can get really brutal sounding. I still love the classic sounds of my JMP at full tilt pushing greenbacks hard though. Speaker breakup is also good, but it just depends upon what you are looking for in your sound. I actually prefer the sounds of the EVM with the Mark IV because it stays so accurate and cannot break up no matter what you do.

 

[diamondschwin]

i just bought some groove tube el34 m tubes and see they have 8 pins as opposed to the stock mesa tubes with 7 pins, im confused? any body got an idea?

 

[rs16iandy]

hi im new here.
I have a mesa f50 with a celestion gold in it and it sounds amazing.
i play classic rock and blues
what would the best out but tubes be for me?
i have
mesa str 430 yellow
mesa str 425 5881 gry
groove tubes 6L6 ge rating 10
they seem to work well but im thinking of putting the 5881s back in

what do you think cheers andy

 

[dodger916]

THIS IS COMPLETELY OPPOSITE WHEN IT COMES TO MESA FIXED BIAS AMPS. In fact, GT distortion rating of 4 has MORE headroom than a 6 rating, not less. Again, this is only relevant for fixed bias amps, and has to do with the percentage of max plate dissipation a tube is pulling at idle. The following link includes a great discussion about this. JOEY B's comments really explain it well. http://forum.grailtone.com/viewtopic.php?f=33&t=39067

I was always sort of fuzzy on what exactly makes a tube compatible with a fixed bias amp like a Mesa Boogie. I'm still fuzzy on specifically what range of value or characterstic of a tube makes it suitable for a Boogie, but a recent correspondence with a representative from Groove Tubes does shed plenty of light upon which Groove Tubes might work in your beloved Mesa Boogie amp.

Me:
"Hi,
I have a Mark IIC and a Dual Rectifier that I'd like to re-tube, and I'm pretty impressed by your 6L6GE tube, and I want to try it, however I'm a bit unsure about how to select a non-Mesa labeled tube that might work best within the limitations imposed by my amps' fixed bias circuitry. What value does Mesa "look at" when testing a power tube to insure it's compatibility with its own amps and thus what should I look for?
Thanks for your assistance.
Sincerely,
-lus casarez"

reply by Myles Rose, Groove Tubes Dude:

"On rating numbers:

Basically, a #1 will distort sooner, and a #10 later. If, for example,
with a mid range tube, say a #5, makes your amp start to break in the
output section at a volume setting on the amp of "4", then with a lower
number tube, like a #2, your amp would have a same sort of break into
output distortion at say a volume setting of "3". With a higher tube,
such as an #8, then you amp would stay clean to about perhaps "6" on
the volume.

High rating numbers are not more or less powerful, they just distort
later. These are preferred by heavy rocker that want maximum clean
output, as they get their distortion and tone from effects or pedals.
These are not as touch dynamic.

Low number tubes are very touch dynamic, and more suited for a
lot of folks, for smaller venues and recording.

Most folks prefer the 4-7 range tubes, as they are the closest in character
and touch to what the amplifier designer had in mind. They are also the most
versatile.

On scale conversions:

On Mesa Boogie amps there are six color codes.
All of them are in the GT 4-6 range. These amps
have a fixed bias to staying in this range is the
same as Mesa tubes.

Mesa vs Groove Tubes scale

Red = 4
Yellow =4
Green =5
Gray =5
Blue =6
White =6"

I don't know about you guys, but I'm breaking out my debt card, going to musician's friend, and hooking up with some GT 6L6GE's!

 

[talltxguy]

Here's a bit data that may help with the Dual Rectifier. I took these measurements from my Roadster 2X12 with stock Mesa rectifier tubes & Groove Tubes E34LS tubes rated at #4:
bold diode 42.3 mA
bold rec 30.6 mA
spongy diode 29.5 mA
spongy rec 21.0 mA
Here are some numbers for JJ E34L with a bias point of 43 (Tube Depot rating):
bold diode 69.0 mA
bold rec 50.1 mA
spongy diode 48.0 mA
spongy rec 34.7 mA

I know this wasn't a great comparison for GT tubes or Mesa tubes, but it does give you a ballpark idea of two different bias points, or numbers, of tubes.

I did not care for the GTs in my Roadster as they were a bit dull and lacking some dynamics. The JJ's were much better but lacked the bass that I get from KT77s, which I currently have in my Roadster. Because they have a bias point of 50 (very hot), I only run them in spongy rectifier (GZ34's) mode. Here are some numbers with the KT77s:
bold settings: way too hot to run without risking damage
spongy diode 54.2 mA (quite hot and avoided by me)

I would suggest getting a bias probe and recording your own data. This way you will know for sure if the #6 GT tubes run hotter than the #4 GT tubes, as I and others think they do, contrary in opinion to what some people - who know more about tube amps than I by the way - think. 8)