Power Tube ?'s

[jads57]

Hi, I'm kind of learning about the whole biasing power tube thing, so forgive my ?'s if they are naive. I've been experimenting w/ different power tubes in my Nomad 55. So far I've tried JJ 6L6's (very nice results) , Mesa STR440's ( harsh sounding), TAD EL34B-STR (sound good so far). Is it just hit and miss w/ the fixed bias afjustment on my Boogie, or would it be better to have the amp modded to have an adjustable bias pot? I say this because I'm not sure how to order tubes other than Mesa's or GT rated tubes 4-7. And I don't care for the Mesa tubes & feel GT charges way too much for their products. What does 4-7 translate to in current plate draw? Thanks in advance again!

 

[Old BF Shred]

An adjustable bias mod is a great thing, but whether it's worth the money, to you, is the question. And you'd only want to do it on an amp after the warranty has expired. Most tube suppliers know what the Mesa's take and get you the right tube.
As far as Groove Tubes, they are a little more expensive, but I have found they are worth it 'cuz they last....(for me, so far anyway).

Be careful about the rating...only GT rated 4, 5 or 6 are acceptable; 7 is not (don't know where people keep getting this).
BTW, the 4, 5 or 6 is per Mesa themselves...and they never said 7. Mesa has also told me the GT's are the only tubes other than Mesa's that won't void their warranty, as the GT quality control rival's Mesa's own.

Having said this, there are other tubes you can try that may very well sound superior to Mesa's and you may have to experiment to find them. The SED =C= are very good....I use their el34 currently in my Ace and they have great clarity.
But in the end only you know what sounds good to you. 8)
Good luck!

 

[jads57]

Thanks for the reply. My Nomad 55, is long out of warranty so maybe I'll go w/ the adjustable bias pot you suggested. A local tech at Savage Amps had installed a set of JJ 6L6GC tubes that sounded very nice last time it was tubed. I just wanted to see how the different brands ounded in comparison.

 

[MrMarkIII]

At one time "7" was acceptable. I guess no longer. Tube quality and recommendations change. Once upon a time, Mesa recommended against the use of 6L6s in the outer sockets of Mark IIIs. Said so in the manual. Later, they changed their minds.
The Word:
"Mesa/Boogie amplifiers employ a preset bias to allow even the least technically oriented player to change tubes themselves and maintain the original brilliant and dynamic response from the amp. The preset bias also means that Mesa will accept a much narrower range of tubes at much closer matching tolerances, considering the window provided by the preset bias. Other manufacturers and distributors accept tubes of much more extreme current draw and match variation under the guise of bias adjustability, claiming that tubes of different current-draw offer different response.

Tubes of similar type can vary slightly in response, but variations are more dependent on the bias adjustment.( For more in depth bias discussion, see Randall Smith's article on biasing in previous Amplitudes newsletters and on our webpage at http://www.mesaboogie.com). In the end, for any amplifier, Mesa tubes are more stringently tested, more closely matched, and from the most consistent and reliable of tube production ranges... the middle. Our tubes don't run hot or cold...They run RIGHT! We test and match the tubes for you, which is less time spent trying to tweak the amps circuitry, and more time playing and searching for tones with the amps tone controls and features.

Mesa/Boogie tubes have a three letter color code at the base of the tube used to group the tubes into matched pairs. These color codes do not apply to different tonal variation (the number and two letter codes with the color code are Production Batch #'s and Tester's initials respectively)."

(Add grains of salt as necessary).

 

[jads57]

Unfortunately the set of Mesa STR440's I put in the amp didn't sound or perform that well. It could be just that set of tubes. But after reading on this , as well as other amp forums a lot of people seem to concur that Mesa's tubes have their share of rejects as much as other brands. I also felt that the previous set of JJ 6L6's sounded and outperformed the set of Mesa STR440's I put in. That's the reason I'm searching out other brands of power tubes. I wish I was happy w/ the Mesa tubes, it sure would be a lot less trouble! Cheers!

 

[jads57]

So I received the powertubes yesterday, on each box their are ratings. The TAD 6L6GC's are rated as follows PC:38, TC:624, and the JJ EL34L's just have a yellow sticker with 44/6.3 on them. I'm assumming the first # is the plate current on both sets, and the 2nd # on TAD's is plate voltage reading? And on the JJ's I`m not sure. The big ? I have is does anyone know if these fit w/in Mesa/Boogies acceptable bias range? Thanks agian in advance!

 

[212Mavguy]

You might not like this answer, but for SURE I'd get that bias pot mod done. When you hear your tubes biased right into their sweet spot you will be thrilled. There will no longer be any difficulties with tube number or color ratings. Peace.

 

[jads57]

Thanks,I 've already put a call to a local tech about that. I was just curious if anyone else here had tried these tubes and what ratings they used. Thanks again.

 

[KH Guitar Freak]

Looks like I might be the rare few that like the STR440s... :?

 

[jads57]

It could be just the particular set of STR 440's I had installed that I didn'T like. Just curious which color coded ones are you using? Thanks~

 

[KH Guitar Freak]

It could be just the particular set of STR 440's I had installed that I didn'T like. Just curious which color coded ones are you using? Thanks~

I still have the stock ones, and I didn't check the colour code, lol...

 

[LerxstLee]

Hi, I'm kind of learning about the whole biasing power tube thing, so forgive my ?'s if they are naive. I've been experimenting w/ different power tubes in my Nomad 55. So far I've tried JJ 6L6's (very nice results) , Mesa STR440's ( harsh sounding), TAD EL34B-STR (sound good so far). Is it just hit and miss w/ the fixed bias afjustment on my Boogie, or would it be better to have the amp modded to have an adjustable bias pot? I say this because I'm not sure how to order tubes other than Mesa's or GT rated tubes 4-7. And I don't care for the Mesa tubes & feel GT charges way too much for their products. What does 4-7 translate to in current plate draw? Thanks in advance again!

__________________________________________________________________________________

I can tell you that if I put mesa red 6l6s into my Roadking, power up all 4, the current draw
using the rectifier mode is 20-21, In diode 29-30 . If I use Tad 6l6wgcstr # (4) ends up the
same result. I had ordered N.O.S. Sylvania 6l6GCs from Brent Jesse , he sent me a matched
quad that again hit the same numbers 20-21 in diode, The GM is marked 7250 with Current marked 59ma ,
and within 10% on the GM and within 2 current numbers, I have to dig to find those.
When I saw 59ma I said no way , but different vendors use different GMs/IP, basically my experience
with these numbers seem to be the way the GM is figured , my TADs were ordered with my request for
a red mesa , the sticker is #4 with the Transconductance around 2700 , and plate current around 22-23.
Lastly I have a quad of GE6l6GCs (n.o.s) with dual harp getters, they came marked tube 1 = 20/89.4
tube 2 = 19.9/89.1 #3 is 21/90.1 #4 is 20/89.1 . These also are right in the early 20s , and early 30s in diode
mode. This tube vendor uses that system.
I still went back to the TADs , still use them, they sound best to me , and I have listened , had others listen ,
I end up with the conclusion that some of the new tubes are as good as some N.O.S , at least the ones I have
and the TAD for new production . The others are in my box of over 100 n.o.s and a few used stock
that are boxed , marked with the vendors "specs" . My notes ect. As you can see the results seem to be the same ,
and the settings on either the brands, and or the machines give you the readings , I have been lucky in getting
what I have asked for as far as plate current and voltage with the amp.

This is my experience with the above if you want to help explain the number system that would be great.

________________________________________________________


Most tube stores will help you get mesa "spec'd tubes .
Here is the GT to mesa spec chart .

The bottom line here is;

Lower numbers will start to distort at lower volume settings on your amp, and have more dynamic touch and feel.
These are the GT 1-3 range, and the Fender "blue" painted tubes. Many Jazz or Blues players like this range, and
they work well for recording where levels are going to be lower, or in smaller venues.

Medium numbers are the most versatile, will drop into most amps and be very close to most factories bias settings,
and are the best general choice for most players wanting a versatile well rounded amp. These are the GT 4-7
range, and the Fender "white" painted tubes. The range of 4,5,6 are able to be used in Mesa Boogie fixed bias
amps, and on the Mesa scale convert roughly to:

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

Nice to keep handy

/cheers