# PSA: current production 12AX7 info chart...



## StevieMac (Mar 4, 2006)

Came across this just today and thought it was well worth sharing. I think it could answer some common questions regarding the general characteristics of many current production 12AX7s. Enjoy:


https://www.amplifiedparts.com/tech-corner/12ax7-comparison-current-made-tubes


----------



## gtrguy (Jul 6, 2006)

And here we go again... cue the 'all 12AX7 tubes sound the same' brigade...


----------



## nonreverb (Sep 19, 2006)

Why? Is that what you're hoping for?
The thing I'd like to know is what is there 1 -10 graph based on? "Relative reference" doesn't really mean anything if it's not based on an actual standard measurement like amplification factor.



gtrguy said:


> And here we go again... cue the 'all 12AX7 tubes sound the same' brigade...


----------



## Steve_F (Feb 15, 2008)

Cool post, thanks!


----------



## Tone Chaser (Mar 2, 2014)

Thanks for the information; there might be something to learn here.


----------



## StevieMac (Mar 4, 2006)

> And here we go again... cue the 'all 12AX7 tubes sound the same' brigade...



Let's not even go there...




nonreverb said:


> Why? Is that what you're hoping for?
> The thing I'd like to know is what is there 1 -10 graph based on? "Relative reference" doesn't really mean anything if it's not based on an actual standard measurement like amplification factor.


I believe it's described under "The Gain Test Setup" near the bottom of the article. I'm no techie though, so I can't comment on the validity of that setup....


----------



## gtone (Nov 1, 2009)

Interesting - thanks for posting this... :^)


----------



## Lincoln (Jun 2, 2008)

a very slippery slope to be sure. 

And I'm no techie either. I did notice however......if you scroll down in the test chart to where the actual frequency response graph is, the response curves are very, very similar. That tells me they will all sound the same with an overall minute variance in gain?? Am I reading that right?


----------



## jb welder (Sep 14, 2010)

Lincoln said:


> the response curves are very, very similar. That tells me they will all sound the same with an overall minute variance in gain?? Am I reading that right?


 Yes you are reading the graph right.
A few considerations:
1) We're talking guitar amps and they are very peaky beasts. A small difference like that may not be noticeable in one amp but more apparent in another. We're usually dealing with a fairly narrow band of mids, with the mid pot cranked, or maybe scooped.
2) Some guys have hearing much more attuned to subtle differences than others. I'm not a member of the "golden ears" crowd, but I've protected my hearing and maybe am more able to focus it, in a way that let's me hear things some of my peers can not. I've no issue with people who are very attuned to their particular "keeper" and every subtle nuance.
3)As far as I know, all these types of graphs are with the amps set up clean. How many tube amp guys set up that way? Why do we assume the response will stay the same when the tubes are pushed into the non-linear "distortion zone"? I think this may be why we can't just say "the graph shows the gains may vary but response curve stays the same, adjust the volume and there will be no difference". That may be true for clean, but I think for distortion, all bets are off.

4)Even if it's all an illusion, placebo effect is a scientifically proven phenomenon, so "no difference" can still have a positive impact on your playing :smile-new:.


----------



## Lincoln (Jun 2, 2008)

jb welder said:


> 3)As far as I know, all these types of graphs are with the amps set up clean. How many tube amp guys set up that way? Why do we assume the response will stay the same when the tubes are pushed into the non-linear "distortion zone"? I think this may be why we can't just say "the graph shows the gains may vary but response curve stays the same, adjust the volume and there will be no difference". That may be true for clean, but I think for distortion, all bets are off.
> :smile-new:.


Now that's a very good point! Clean is one thing, but who knows what happens under distortion.


----------



## Church-Audio (Sep 27, 2014)

Tubes do sound different anyone that can't hear that should stop playing if they are a tech should fix cars for a living instead of amps lol. I guess that's pretty much as blunt as I can be.


----------



## hollowbody (Jan 15, 2008)

Interesting, nonetheless. I've been using the Tung-Sols in all my amps for the last few years, but I'd like to give those Mullards a go to see how I like them.


----------



## Steve_F (Feb 15, 2008)

hollowbody said:


> Interesting, nonetheless. I've been using the Tung-Sols in all my amps for the last few years, but I'd like to give those Mullards a go to see how I like them.


Agreed, the new tung-sol tubes have been my fave new tubes for a few years now


----------



## Church-Audio (Sep 27, 2014)

Love tungsol 12ax7 tubes sound great. But they don't like certain Mesa boogies and others that use cathode follower circuits. The tube seems to die pretty quickly in these amps. In Mesa boogies I use the preferred series 12ax7 for v1 and 12ax7b for the remainder. But in fender and in any other amp they sound great.


----------



## nonreverb (Sep 19, 2006)

I'd be very careful with "blunt" statements like that Chris. I fix amps just fine and I still don't entirely buy into all that crap on the internet. There may be some truth to it but as jb welder quite nicely points out there are a lot of variables at play.....Throwing out a terse statement like that with nothing to back it up won't impress many here.



Church-Audio said:


> Tubes do sound different anyone that can't hear that should stop playing if they are a tech should fix cars for a living instead of amps lol. I guess that's pretty much as blunt as I can be.


----------



## greco (Jul 15, 2007)

Church-Audio said:


> Tubes do sound different anyone that can't hear that should stop playing.....


I guess my days of playing are now virtually over....sigh.....:sSig_help:


----------



## Steve_F (Feb 15, 2008)

hear this experiment in action:

https://www.youtube.com/watch?v=VkjVvTRP1h0


----------



## WCGill (Mar 27, 2009)

nonreverb said:


> There may be some truth to it but as jb welder quite nicely points out there is a lot of variables at play.....


True that, and if you're auditioning different 12AX7's in an amp with a feedback loop, it can be pretty subtle.


----------



## WCGill (Mar 27, 2009)

Church-Audio said:


> Love tungsol 12ax7 tubes sound great. But they don't like certain Mesa boogies and others that use cathode follower circuits. The tube seems to die pretty quickly in these amps. In Mesa boogies I use the preferred series 12ax7 for v1 and 12ax7b for the remainder. But in fender and in any other amp they sound great.


The Russian tubes don't have very robust cathode-heater voltage ratings it seems. Chinese and JJ tubes are much better in the cathode-follower position.


----------



## nonreverb (Sep 19, 2006)

Indeed. There was a Mesa service bulletin a few years back indicating that Sovtek 12AX7A were not recommended for cathode follower circuits due to drop out.



WCGill said:


> The Russian tubes don't have very robust cathode-heater voltage ratings it seems. Chinese and JJ tubes are much better in the cathode-follower position.


----------



## loudtubeamps (Feb 2, 2012)

WCGill said:


> True that, and if you're auditioning different 12AX7's in an amp with a feedback loop, it can be pretty subtle.


Subtle indeed Mr. Gill.









12AX7 Comparison of Current Made Tubes | Antique Electronic Supply


----------



## Church-Audio (Sep 27, 2014)

I absolutely stand by my words lol tubes do sound different. I hear it all the time. Heard it today. But to each his or her own. My belief goes unchanged  I've been playing for 35 years been a sound engineer for 25 plus years and a amp tech for over 27 plus years. I hear it all the time. For sure different tubes sound different in certain circuits and certain tubes sound better than others in certain circuits. Tubes like mallards sound different than just in any circuit you put them in. It's not snake oil.... It's reality can I explain why? Nope do I care nope my professional customers know what I know they sound different. Anyway it's my opinion. Everyone has one about this subject do t they  also the test above is fundamentally flawed for so many reasons it's not funny. It was not carried out properly and I can tell that just by looking at the graphs. The input gain was not calibrated. Because none of the overlays ever match up anywhere lol. It's impossible for that to be accurate with out absolutely matching input level. But what do I know I e been measuring sound systems and doing complex acoustic measurements since we had the ability to do so with a computer  party on say what you want I stand by my words.


----------



## nonreverb (Sep 19, 2006)

We already know that Chris.....some here with as much experience or more don't agree. Nobody said you were not entitled to your opinion. However, if you talk to your customers the way you talk here to your peers, that might be a problem for you.



Church-Audio said:


> I absolutely stand by my words lol tubes do sound different. I hear it all the time. Heard it today. But to each his or her own. My belief goes unchanged  I've been playing for 35 years been a sound engineer for 25 plus years and a amp tech for over 27 plus years. I hear it all the time. For sure different tubes sound different in certain circuits and certain tubes sound better than others in certain circuits. Tubes like mallards sound different than just in any circuit you put them in. It's not snake oil.... It's reality can I explain why? Nope do I care nope my professional customers know what I know they sound different. Anyway it's my opinion. Everyone has one about this subject do t they  also the test above is fundamentally flawed for so many reasons it's not funny. It was not carried out properly and I can tell that just by looking at the graphs. The input gain was not calibrated. Because none of the overlays ever match up anywhere lol. It's impossible for that to be accurate with out absolutely matching input level. But what do I know I e been measuring sound systems and doing complex acoustic measurements since we had the ability to do so with a computer  party on say what you want I stand by my words.


----------



## Steve_F (Feb 15, 2008)

I also agree they change the sound. I put some of my favorite old English made Phillips 12AX7's in my Rocker 30 over the weekend and it lost a noticeable amount of gain. The amp is a little smoother and has a bit more clarity. It's not necessarily better or worse and I haven't decided if I'll keep the tubes in there but it is different for sure.


----------



## nonreverb (Sep 19, 2006)

That's quite possible. If they've had many hours use, their emission is probably noticeably lower than they were new.



Steve_F said:


> I also agree they change the sound. I put some of my favorite old English made Phillips 12AX7's in my Rocker 30 over the weekend and it lost a noticeable amount of gain. The amp is a little smoother and has a bit more clarity. It's not necessarily better or worse and I haven't decided if I'll keep the tubes in there but it is different for sure.


----------



## hollowbody (Jan 15, 2008)

I just listened to the video, but being at work, I don't have access to my nice monitors and also it seems like the audio quality is fairly uninspiring to begin with. From what I did hear, though, it seemed like some very minor changes, which makes sense. There was one pair of tubes that sounded identical to me. The most obvious were the first two (Sovtek to Mullard), but despite the Mullard's high ratings, I didn't enjoy it was much as the Tung-Sols in that video. I think I'm just going to stick with the Tung-Sols.


----------



## LydianGuitars (Apr 18, 2013)

The methodology for testing is important. A graph on its own means nothing without knowing what the methodology is and a good understanding of what to look for (i.e 1db difference can be heard). 
In my unscientific experience, for example, I found that a JJ 12AX7 preamp tube is darker than a Shuguang but the Tung Sol seems to be bright but with better clarity than Shuguangs. 

A single, clean frequency sweep won't show that behaviour in an overdriven guitar amp.


----------



## WCGill (Mar 27, 2009)

Church-Audio said:


> I absolutely stand by my words lol tubes do sound different. I hear it all the time. Heard it today. But to each his or her own. My belief goes unchanged  I've been playing for 35 years been a sound engineer for 25 plus years and a amp tech for over 27 plus years. I hear it all the time. For sure different tubes sound different in certain circuits and certain tubes sound better than others in certain circuits. Tubes like mallards sound different than just in any circuit you put them in. It's not snake oil.... It's reality can I explain why? Nope do I care nope my professional customers know what I know they sound different. Anyway it's my opinion. Everyone has one about this subject do t they  also the test above is fundamentally flawed for so many reasons it's not funny. It was not carried out properly and I can tell that just by looking at the graphs. The input gain was not calibrated. Because none of the overlays ever match up anywhere lol. It's impossible for that to be accurate with out absolutely matching input level. But what do I know I e been measuring sound systems and doing complex acoustic measurements since we had the ability to do so with a computer  party on say what you want I stand by my words.


I'm not sure I understand your reference to input gain calibration and mismatch. Care to elaborate?


----------



## jb welder (Sep 14, 2010)

So is there some law there that requires all the current manufacturers to match each other in terms of emission new out of the box for any given tube type? :smile-new:


----------



## dcole (Oct 8, 2008)

No law. Typically an engineer would account for variance in tube production and design the circuit such that those variances don't effect how things operate as much.


----------



## WCGill (Mar 27, 2009)

And in this case when you're testing the variance of the tubes?


----------



## Church-Audio (Sep 27, 2014)

In order to do a frequency sweep measurement each tube being used must have its input and output calibrated. So that each tube being swept gives the same starting point for measurement. If not you don't have a meaningful test. You just have a pretty graph. And I would have done it before the onboard eq I would have done it before because we are not so much interested in the effects of the circuit. We are interested in the actual tube response. Things like plate voltage would also need to be tweaked for each tube so that the playing field was fair. Then if there are differences you could really see them. Most amp techs do t have my background. Of doing acoustic measurements. There is a scientific way tests need to be conducted in order to be meaningful and the basis of that is input level and output level calibration. Also different circuit topologies should be used because of things like miller capacitance and the interactive nature of each basic type of circuit like fender vrs Marshall vrs vox. But there is a limit to how involved you want to get. This is a chicken or the egg argument. What came first to change the tone if an amp? The circuit or the tube? Certainly it's been my experience that different tubes sound different in different amps. Different tubes again in my experience sound different in the same amp. So I believe personally it's a combination of things. So if we are looking at just tubes we want a flat test rig if not we are wasting time trying to compare tubes frequency response in the first place. Like I say the test is fundamentally flawed. 

And no I don't talk in a disrespectful way ever, but it's really frustrating to see some of the misinformation being spread around in forums like this and many others.


----------



## nonreverb (Sep 19, 2006)

"Tubes do sound different anyone that can't hear that should stop playing if they are a tech should fix cars for a living instead of amps lol. I guess that's pretty much as blunt as I can be."

Sorry but I found your comment arrogant and disrespectful to both the players and the techs alike on this forum....There's no need for this. Your last post was far more informative if not more mature.



Church-Audio said:


> In order to do a frequency sweep measurement each tube being used must have its input and output calibrated. So that each tube being swept gives the same starting point for measurement. If not you don't have a meaningful test. You just have a pretty graph. And I would have done it before the onboard eq I would have done it before because we are not so much interested in the effects of the circuit. We are interested in the actual tube response. Things like plate voltage would also need to be tweaked for each tube so that the playing field was fair. Then if there are differences you could really see them. Most amp techs do t have my background. Of doing acoustic measurements. There is a scientific way tests need to be conducted in order to be meaningful and the basis of that is input level and output level calibration. Also different circuit topologies should be used because of things like miller capacitance and the interactive nature of each basic type of circuit like fender vrs Marshall vrs vox. But there is a limit to how involved you want to get. This is a chicken or the egg argument. What came first to change the tone if an amp? The circuit or the tube? Certainly it's been my experience that different tubes sound different in different amps. Different tubes again in my experience sound different in the same amp. So I believe personally it's a combination of things. So if we are looking at just tubes we want a flat test rig if not we are wasting time trying to compare tubes frequency response in the first place. Like I say the test is fundamentally flawed.
> 
> And no I don't talk in a disrespectful way ever, but it's really frustrating to see some of the misinformation being spread around in forums like this and many others.


----------



## jeancoltrane (Feb 20, 2015)

in my times of tube swapping, id say it definitely makes a noticeable difference - especially if you play with a cranked amp. even more so if you throw a fuzz in front ; ) im not an amp tech, so i dont know if the voltages etc were equal but i think that is a valid point chris is trying to make. 

i still have nightmares from the time an amp tech said my telefunken 6ca7s and mullard 12ax7s were pooched, and proceeded to replace all of them with new JJs to bring the amp 'up to spec' (about 20 tubes). well, my amp came back sounding completely lifeless, and basically like crap despite all the $$ i just piled into her. infact, the brand new JJ tubes didnt work properly with my magnatones vibrato circuit, and i spent more $$ with more techs trying to get that issue sorted until i pulled the old vibrato tube out of my hammond L100 and it completely fixed the problem. the amp tech was one of those guys that didnt believe tubes had any inherent tone, and i spent literally thousands to make my amp worse off. so i am definitely very skeptical of techs that dont believe in tube tone differences (or cant discern them). count that as an expen$ive le$$on learned...

edit: forgot to mention i put my old "garbage" tubes back in and the amp had beautiful tone again. i now have drawer full of 20 JJ tubes.


----------



## WCGill (Mar 27, 2009)

Church-Audio said:


> In order to do a frequency sweep measurement each tube being used must have its input and output calibrated. So that each tube being swept gives the same starting point for measurement. If not you don't have a meaningful test. You just have a pretty graph. And I would have done it before the onboard eq I would have done it before because we are not so much interested in the effects of the circuit. We are interested in the actual tube response. Things like plate voltage would also need to be tweaked for each tube so that the playing field was fair. Then if there are differences you could really see them. Most amp techs do t have my background. Of doing acoustic measurements. There is a scientific way tests need to be conducted in order to be meaningful and the basis of that is input level and output level calibration. Also different circuit topologies should be used because of things like miller capacitance and the interactive nature of each basic type of circuit like fender vrs Marshall vrs vox. But there is a limit to how involved you want to get. This is a chicken or the egg argument. What came first to change the tone if an amp? The circuit or the tube? Certainly it's been my experience that different tubes sound different in different amps. Different tubes again in my experience sound different in the same amp. So I believe personally it's a combination of things. So if we are looking at just tubes we want a flat test rig if not we are wasting time trying to compare tubes frequency response in the first place. Like I say the test is fundamentally flawed.
> 
> And no I don't talk in a disrespectful way ever, but it's really frustrating to see some of the misinformation being spread around in forums like this and many others.


As well, I don't mean to be disrespectful, but your logic is flawed. How do you calibrate a tube's input and output?


----------



## Church-Audio (Sep 27, 2014)

Um the software and a volt meter. Thats how you calibrate the input and output. All software has controls for input and output. Thats how you make sure you are getting accurate testing between tubes. You first have to make sure they are all adjusted so they are giving the same exact input level into the computer so when you make a comparison it means something. And some software like mine will allow you to do a RMS input measurement. You are using a generator built into the program so you have to make sure that is set to the same exact level for each tube. Then you calibrate the output of the tube so it reads the same on all tubes. Then any differences you have are frequency response differences of the tubes themselves. Its pretty simple.


----------



## Church-Audio (Sep 27, 2014)

Well your entitled to your opinion and so am I. Arrogant is the last thing I am frustrated by the misinformation is more like it.


----------



## WCGill (Mar 27, 2009)

I guess I'm too stupid to understand it Chris. I think that subbing in different tubes into the same circuit and measuring response would yield varying and valid results, pretty simple. I don't have "Um the software" and I don't have your background so I guess I'm out of the loop on this one.


----------



## Church-Audio (Sep 27, 2014)

Well um... lol its like this... Every tube even though you might measure it for gain will not be putting out exactly the same level. Think of it like this.. You have a microphone that measures frequency response. The speakers being measured are exactly the same distance from the mic. The mic it self is calibrated for level. So you put a sweep through the speaker say from 20hz to 20khz. The "average" input level coming into the mic should be the same. So the differences might be that each speaker has a slightly different sensitivity. So we have to make sure that we account for that in the measurement by re "calibrating" the output of each speaker so the mic measures the same average input level. This gives us a starting point so that any difference we see in the overlay of the graphs is purely frequency response and not level differences of the sensitivity of each speaker. This could give the impression for example that one speaker has more top end or low end. 

Anther example is measuring distortion.
You have two tubes.. Your going to measure the THD of each tube.. You would want to make sure that the input at the very least was the same for both tubes because lets say one input is higher than the other this might influence the results of the test. One tube with the higher input level might show higher distortion. One tube with the lower input level might show lower distortion. Thus the results are not reliable. 

When you overlay graphs of frequency response you have to make sure the device being measured is at the exact same input and output level as all of the other devices being measured that way when you see differences on a graph that is overlayed you will know that they truly are frequency response related differences and not level differences making it look like frequency response differences. 

Again I am not Mr science I believe in using my ears first test gear second. And I think its cool someone went to the trouble to measure tubes response curves but its not a very revealing way to do it with the basic level flaws. If I had more time I would do this myself but I am super busy with repairs and my microphone business.


----------



## nonreverb (Sep 19, 2006)

Do you have print outs of all these tubes you've tested with comparisons?


----------



## Church-Audio (Sep 27, 2014)

nonreverb said:


> Do you have print outs of all these tubes you've tested with comparisons?


Read my last post above your comment the last part of it. My whole thing was not to upset anyone but I can see I've ruffled some feathers the test shown is still no less incorrect in the way it was conducted..... I know you don't like me and that's ok I can live with that. But I'm still correct. Like it or not. Anyways back to work got things to fix.


----------



## nonreverb (Sep 19, 2006)

I never said I don't like you Chris....I just don't get your behaviour sometimes. This forum is a place to discuss ideas and inform. It should not however, be a place to pass judgment on others or infer that some are less than just because they don't buy into one's statements. As for correctness, you can believe your completely correct, that's entirely your right...It doesn't mean others will agree and many may be excellent techs. This group was active for many years before you arrived and it's contributers are some of the most respectable techs I've had the pleasure of interacting with. I would think you'd want to be a more proactive contributer instead of just another pontificator. Anyway....enough already! I'll shut up now.



Church-Audio said:


> Read my last post above your comment the last part of it. My whole thing was not to upset anyone but I can see I've ruffled some feathers the test shown is still no less incorrect in the way it was conducted..... I know you don't like me and that's ok I can live with that. But I'm still correct. Like it or not. Anyways back to work got things to fix.


----------



## 2manyGuitars (Jul 6, 2009)




----------

