Mesa/Boogie Nomad 55 Plate Voltage?
Moderators: pompeiisneaks, Colossal
Mesa/Boogie Nomad 55 Plate Voltage?
Hi, What is the plate voltage on my Nomad 55 in both 6L6GC & EL34 modes? I ask this because I'm trying some new tubes other than Mesa/Boogie STR440 ( don't like) or Groove Tubes 4-7 rating ( too expensive!) So I'm trying TAD 6L6GC, and a set of JJ EL34L's. I want to make sure they are in the acceptable range limits of my amp's fixed bias. Thanks in advance!
Re: Mesa/Boogie Nomad 55 Plate Voltage?
How is knowing the plate voltage going to tell you if the tubes will bias right? The only way you're going to know for sure is if you measure it.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Bias is correct, when Ua*Ia is no more than 70-80%Jana wrote:How is knowing the plate voltage going to tell you if the tubes will bias right? The only way you're going to know for sure is if you measure it.
of plate dissipation.
IE: if Ua = 350VDC then 57mA bias for EL34 (25W) is correct.
If Ua is 500VDC then 57mA bias is out of range (plate glowing)!
You must to set bias no more than 40mA.
Max bias is: 0,8*Pa/Ua
Now it's clear, Jana?
Re: Mesa/Boogie Nomad 55 Plate Voltage?
No, it's not clear.
Mesa Boogie's have a bias that is fixed, as in non-adjustable (unless you want to change resistors).
Just because one set of tubes is biased correctly at a given plate voltage does not mean that another set of tubes will be biased at the proper current with the same bias voltage.
I am well familiar with how to calculate plate dissipation. However, the figures and formulas you give do not take into consideration the bias voltage that is required to achieve the desired plate dissipation.
Mesa Boogie's have a bias that is fixed, as in non-adjustable (unless you want to change resistors).
Just because one set of tubes is biased correctly at a given plate voltage does not mean that another set of tubes will be biased at the proper current with the same bias voltage.
I am well familiar with how to calculate plate dissipation. However, the figures and formulas you give do not take into consideration the bias voltage that is required to achieve the desired plate dissipation.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Sorry guys, not trying to stir things up. I'm just trying to find out how to order the correct rated power tubes (both EL-34,& 6L6GC ) for my Mesa/Boogie Nomad 55, other than Mesa's or Groove Tubes. Thanks again in advance
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Because they want your business, most sellers that rate and match tubes have the Mesa and other propriatary systems figured out. If you contact, for instance, thetubestore.com and tell them "Mesa says I have to use the blue ones", they know what that means relative to their rating system.
good luck
W
good luck
W
Re: Mesa/Boogie Nomad 55 Plate Voltage?
nothing stirred up on my end.
Unless you find someone who can test and rate the TAD and JJ tubes with some sort of scale that corresponds to the Boogie/GT scale, you won't know for sure what the tubes are biasing at.
If you really want to try these other tubes then this is what I would suggest: some places, like Thetubestore.com for example, have a number on their tubes for where they bias at. As far as I know, it does not relate to GT ratings, but is simply a way so that once you bias the amp with that set of tubes, you can reorder tubes and tell them that number. Then they pick another set with the same number and all you do is plug the tubes in an play. But, what you will have to do initially is to set the bias for those tubes.
Unless you find someone who can test and rate the TAD and JJ tubes with some sort of scale that corresponds to the Boogie/GT scale, you won't know for sure what the tubes are biasing at.
If you really want to try these other tubes then this is what I would suggest: some places, like Thetubestore.com for example, have a number on their tubes for where they bias at. As far as I know, it does not relate to GT ratings, but is simply a way so that once you bias the amp with that set of tubes, you can reorder tubes and tell them that number. Then they pick another set with the same number and all you do is plug the tubes in an play. But, what you will have to do initially is to set the bias for those tubes.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Wayne beat me to it, I guess Thetubestore does know. Give them a ring, I have ordered tubes from them before and they are fast and have good service.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Thanks for the info, that helps to know what to ask for.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
jads-
Are you planning on just dropping the tubes in without having the bias checked? I wouldn't do that even with Mesa tubes, let alone with another brand. Considering the quality variations of new production tubes these days, I would hope that you or your tech would at least measure the bias to see if it is an acceptable range.
Are your current tubes shot? If not, you (or your tech) can measure the various voltages and current draw, and then once you change the tubes, you can measure again to see how they match up. Mesa claims that their settings are "perfect" for the amp and tubes supplied (don't blame me for thie hype), so in theory, you would want tubes that also achieve that "perfection"
Personally, i think it is a bunch of BS. have your tech install a bias pot, and go with the best tubes you can afford. Then adjust the pot to achieve the best tone while staying within a safe range.
Also, that 70%-80% stuff is not really a hard and fast rule. It is more of a guideline that some techs / designers follow, while others blow right past it without any negative results. For example the Rocket bias is set pretty close to 100% as I understand it. And it sounds awsome. maybe the tubes will have a slightly shorter l;ife as a result, but I'll take tone over tube life anyday (as long as it is not measured in minutes).
Are you planning on just dropping the tubes in without having the bias checked? I wouldn't do that even with Mesa tubes, let alone with another brand. Considering the quality variations of new production tubes these days, I would hope that you or your tech would at least measure the bias to see if it is an acceptable range.
Are your current tubes shot? If not, you (or your tech) can measure the various voltages and current draw, and then once you change the tubes, you can measure again to see how they match up. Mesa claims that their settings are "perfect" for the amp and tubes supplied (don't blame me for thie hype), so in theory, you would want tubes that also achieve that "perfection"
Personally, i think it is a bunch of BS. have your tech install a bias pot, and go with the best tubes you can afford. Then adjust the pot to achieve the best tone while staying within a safe range.
Also, that 70%-80% stuff is not really a hard and fast rule. It is more of a guideline that some techs / designers follow, while others blow right past it without any negative results. For example the Rocket bias is set pretty close to 100% as I understand it. And it sounds awsome. maybe the tubes will have a slightly shorter l;ife as a result, but I'll take tone over tube life anyday (as long as it is not measured in minutes).
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Even though there seems to be some consensus on this subject,there's enough different opinions to make it even more confusing! The one thing I'm going to do is go to a qualified tech! Thanks everyone for their input.
Re: Mesa/Boogie Nomad 55 Plate Voltage?
Good decision.jads57 wrote:Even though there seems to be some consensus on this subject,there's enough different opinions to make it even more confusing! The one thing I'm going to do is go to a qualified tech! Thanks everyone for their input.