No Differences When Changing Tubes?

That's to be expected. The earlier in the signal chain the change happens, the more effect it can have further down the line as it gets amplified by following stages. It also depends on the amp as well. With many modern high gain amps, the power section runs quite clean and the bulk of the distortion and tonal shaping happens in the preamp section.
 
I've said it before, and I'll say it again:

We need some flowcharts, at the very least, for stuff like this. I'm not a stupid or lazy person, I just don't have the time to dive off into figuring out a tube's trainconductorance when it should be "I changed the tube type, and all affected parameters were automatically adjusted for it" type thing. People in the real world don't have to have a doctorate degree in electrical engineering to hear a difference when swapping tubes, but instead just swap the tubes and a switch on the back of the amp in most cases.
 
biggness said:
I've said it before, and I'll say it again:

We need some flowcharts, at the very least, for stuff like this. I'm not a stupid or lazy person, I just don't have the time to dive off into figuring out a tube's trainconductorance when it should be "I changed the tube type, and all affected parameters were automatically adjusted for it" type thing. People in the real world don't have to have a doctorate degree in electrical engineering to hear a difference when swapping tubes, but instead just swap the tubes and a switch on the back of the amp in most cases.
Click to expand...
It wouldn't be too hard, if the needed data was available in a couple nice arrays, to set up a calculator that let you pick an amp, and a tube type, and have it calculate a XFormer Matching scalar for you. Pretty simple to do as a JS app in a web page.
 
FractalAudio said:
For example a 6CA7 has a transconductance of around 10 mmhos. A KT66 is around 6 mmhos. So you would set transformer match to 0.6 for the KT66 if the default tube was 6CA7.

6550, EL34 and 6CA7 all have roughly the same transconductance (10-11 mmhos or so). They have different kvb though which affects the harmonic series (like shown above).

The other way to do it is to look up what the recommended load impedance is. For example a pair of 6L6 has a recommended load of around 4K. A pair of EL34 is 3.2K. So if you replace EL34s with 6L6 then you would reduce transformer match to 3.2/4 = 0.8.
Click to expand...

Joe Bfstplk said:
It wouldn't be too hard, if the needed data was available in a couple nice arrays, to set up a calculator that let you pick an amp, and a tube type, and have it calculate a XFormer Matching scalar for you. Pretty simple to do as a JS app in a web page.
Click to expand...

So thanks to Cliff, we already have a few ballpark numbers from above:

6550 / EL34 / 6CA7 : XFormer Match ~ 0.9-1.1​
​
6CA7 -> KT66: XFormer Match ~ 0.6​
KT66 -> 6CA7: XFormer Match ~ 1.6​
​
EL34 -> 6L6: XFormer Match ~ 0.8​
6L6 -> EL34: XFormer Match ~ 1.25​

Given the raw transconductances Cliff use for each tube (if he's willing to share), it'd be easy to put together a lookup table with transconductance and recommended impedance load for each tube type and make a Xformer Match lookup table (or calculator) with the calculations from each method - which might be a little different. (Swapping in reverse would be the reciprocal I assume.)
 
Last edited:
Piing said:
If you cannot get a tone from the Axe-FX III that fully satisfies you without "swapping tubes", I am afraid that you will never be fully satisfied with your tone ;)
Click to expand...

I love my tone. That said, there’s nothing wrong with wanting to experiment with Axe FX’s features. It’s the only way to learn. I’m relatively new to it and still have a ton to learn. What better way than here? This might be the best forum I’ve ever been a member of. There are people here who have forgotten more than I know and I’m learning so much just by being a fly on the wall
 
Jirai said:
That is a cocktail of languages I say. Besides English and German there are a bunch of words which seem to be home made. My first thought was Yiddish...
Click to expand...
It's a fractured combination of German and English, intended for an English-speaking audience. It's loosely based on German because, at the time it was written, a significant portion of America's scientists and engineers were German immigrants. The homemade words are designed to be at least partially decipherable by native English speakers.
 
biggness said:
I've said it before, and I'll say it again:

We need some flowcharts, at the very least, for stuff like this. I'm not a stupid or lazy person, I just don't have the time to dive off into figuring out a tube's trainconductorance when it should be "I changed the tube type, and all affected parameters were automatically adjusted for it" type thing. People in the real world don't have to have a doctorate degree in electrical engineering to hear a difference when swapping tubes, but instead just swap the tubes and a switch on the back of the amp in most cases.
Click to expand...

The thing is it is already integrated in the way it should be. It changes all the parameters to fit the new tubes best.
The problem with that is that in the real world people commonly do NOT change their amp components to fit the new tubes resulting in much more pronounced differences in tone.
Anyway, I also think we should have the choice wether the Axe Fx changes all the others parameters to fit the tubes or not, maybe by adding a switch. I actually made a wishlist thread about it some time ago. But at that time no one seemed very interested in it.
 
Lilarcor said:
The thing is it is already integrated in the way it should be. It changes all the parameters to fit the new tubes best.
The problem with that is that in the real world people commonly do NOT change their amp components to fit the new tubes resulting in much more pronounced differences in tone.
Anyway, I also think we should have the choice wether the Axe Fx changes all the others parameters to fit the tubes or not, maybe by adding a switch. I actually made a wishlist thread about it some time ago. But at that time no one seemed very interested in it.
Click to expand...
Hmm, are you sure it automatically changes the related settings when you change tubes? I thought the whole point if the transformer match discussion above was that it didn't. But maybe I'm confused.
 
When you change the tube type in the amp block things like the simulated output transformer are also changed to fit the tube type best. This means that there is no transformer mismatch (transformer match value stays at 1.0) because the simulated transformer was changed with the tube type. This negates most of the tone and feel differences you experience when changing the power tube type of a real amp because in this case you usually don't change the output transformer etc., as well. To simulate the resulting transformer mismatch you can change the transformer match value in the amp block ....
... or hope for Cliff adding the possibility to disable the "auto match feature".
 
To clarify ....by FAS implementing the feature of swapping power tubes .....he has in his words “normalized” the transconductance variations.

This facilitates quick auditions and experimentations of the feature.

To set the Transformer Match to model real world specs .....he gave 2 options.

1. Look up the transconductance information for the tubes and adjust the Transformer Match accordingly.

2. Look up the impedance load of the tubes and adjust the Transformer Match accordingly

Joe Bfstplk was kind enough to link some manufacturer tube specs 👍🏻

https://forum.fractalaudio.com/threads/no-differences-when-changing-tubes.163545/post-1961127
 
Rex said:
It's a fractured combination of German and English, intended for an English-speaking audience. It's loosely based on German because, at the time it was written, a significant portion of America's scientists and engineers were German immigrants. The homemade words are designed to be at least partially decipherable by native English speakers.
Click to expand...
Thanks for the explanation, I was not sure whether it was a real sign. It's interesting, that they thought that such a weird mix would be easier to understand than proper English or German.
 
Jirai said:
Thanks for the explanation, I was not sure whether it was a real sign. It's interesting, that they thought that such a weird mix would be easier to understand than proper English or German.
Click to expand...
It's a joke Jirai :)

It's English with a bunch of kinda funny fake German not-really-words thrown in. Language-specific humor.

And you probably know all that and I'm being the meta-fool for explaining :)
 
Jirai said:
Thanks for the explanation, I was not sure whether it was a real sign. It's interesting, that they thought that such a weird mix would be easier to understand than proper English or German.
Click to expand...
Yes, it was a real sign. An inside joke among engineers and technicians. We'd post it in our cubicles as a source of team pride in our collective knowledge, or sometimes in a room that contained technical equipment that might be visited by nontechnical people, to remind them that playing with the equipment might produce undesired results.

The fractured German didn't make it easier to understand. In fact, it required the reader to stop and read it slowly. The choice of words also made it light-hearted enough that it wouldn't offend the people whom it was directed at.
 
Rex said:
Yes, it was a real sign. An inside joke among engineers and technicians. We'd post it in our cubicles as a source of team pride in our collective knowledge, or sometimes in a room that contained technical equipment that might be visited by nontechnical people, to remind them that playing with the equipment might produce undesired results.

The fractured German didn't make it easier to understand. In fact, it required the reader to stop and read it slowly. The choice of words also made it light-hearted enough that it wouldn't offend the people whom it was directed at.
Click to expand...
Thanks, now I got it. Obviously it's a commonly known joke in US, but in this part of the world...
 
  • Like
Reactions: Rex
Jirai said:
Thanks, now I got it. Obviously it's a commonly known joke in US, but in this part of the world...
Click to expand...
Different cultures, different humor, different experiences. I don't know if it would be possible to create such a sign that would work the same way in Japan.
 
Jirai said:
Thanks, now I got it. Obviously it's a commonly known joke in US, but in this part of the world...
Click to expand...
Yeah, guilty as charged for using US/Anglo-centric humor. The only vaguely tangentially-related-to-Japanese joke I know is this:
My ex wife studied Japanese for four semesters at ASU in the mid '90s. The only phrase I picked up was, "A tama ga itai." True story, sadly....
 
You must log in or register to reply here.
Back
Top Bottom