No Differences When Changing Tubes?

[Jirai]

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.

Japanese humour is quite different I say.

 

[Jirai]

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....

Well, it's a start...

 

[JDR3009]

The thing that confuses me is hat there seems to be options that undermine themselves, unless I’m misunderstanding.

I get Cliff’s explanation of power tubes not having an intrunsic ‘sound’ unto themselves, but when changing power tubes in a physical amp (6l6 to el34 for example) there seems to be much more difference than in the AFX.

Someone (sorry, I don’t remember their name!) explained to me on here that it’s not so much the tubes that change the sound but how they interact with the surrounding circuitry. If a tube is starved because the circuitry around it is built for a different type of tube, then it’d sound different when the sound is put out, or at least that’s what you’d expect. I’d also had it explained to me by someone (again, I forget the name, sorry) that the AFX effectively changes the modelled circuitry so that these kinds of mismatches don’t happen inside the unit.

If that’s correct, it defeats the entire purpose of power tube switching, surely? Things sound as they do in the real world because of the interaction between parts in the circuit, so changing the internal circuitry to stop those mismatches or whatever else is going on leads to things sounding the same, whether they use 6l6, el34, kt77, whatever. Plus, in the digital world, those mismatches or whatever other quirks are even safer to use as they can’t overheat or break down or have those kinds of problems. I can run a 400 watt bass amp through a 1x10 Alnico Blue speaker inside the AFX, if I did that in the real world it’d ruin my day real fast.

 

[MisterE]

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.)

I asked the same thing (see post #58)
But I fear it's not that simple.
I've been going through some datasheets and a The Tuba Amp Book that I had lying around and it seems - correct me if I'm mistaken - that it also depends on the type of amp. I see only a value for transconductance for a Class A amp. And it also depends on the plate voltage. Same for the load resistance.

 

[FractalAudio]

I asked the same thing (see post #58)
But I fear it's not that simple.
I've been going through some datasheets and a The Tuba Amp Book that I had lying around and it seems - correct me if I'm mistaken - that it also depends on the type of amp. I see only a value for transconductance for a Class A amp. And it also depends on the plate voltage. Same for the load resistance.

Yes, you can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

Those amps where you can use different power tubes don't swap the transformer. They just rebias the tubes. If the transformer turns ratio is optimized for 6L6s installing EL34s will cause the transformer to be slightly undermatched which is the primary reason the tone changes. Conversely if the transformer is optimized for EL34s installing 6L6s will cause it to be overmatched.

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you. Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps.

Frankly all this compalining about something you have far more control over sounds entitled and whiny.

 

[Budda]

(might as well lock it up, no?)

 

[Joe Bfstplk]

Yes, you can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

Those amps where you can use different power tubes don't swap the transformer. They just rebias the tubes. If the transformer turns ratio is optimized for 6L6s installing EL34s will cause the transformer to be slightly undermatched which is the primary reason the tone changes. Conversely if the transformer is optimized for EL34s installing 6L6s will cause it to be overmatched.

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you. Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps.

Frankly all this compalining about something you have far more control over sounds entitled and whiny.

So would we set the mismatch for plate load to xfmr load ÷ recommended load, based on the amp and the tube data, then? Given a list of amp models' OT primary loads and the recommended plate loads from tube data, it would not be hard to build a calculator. The only question is, for models where the designer varied from the recommended load, does this variance need to be taken into account, since the model has this designed-in mismatch baked in? 4.2k Fenders are a bit lower than the 6L6 sheets claim is optimal, and that changes the response and harmonic content a bit.

I'd be happy to build it as a web-based tool for folks to use, and either host it myself or make the code available for FAS to host it, given the amp OT primary info needed to build it....

 

[MisterE]

Frankly all this complaining about something you have far more control over sounds entitled and whiny.

No complaining and whining here.
Just stating what I found.
I know we're not supposed to pursue the imitation of the real thing and but it's a OCD thing where I wanted to use the real values to do something like Joe Bfstplk is proposing just to see (or hear) how it would work in the real world.
I resorted to the old "use your ears" and adjusted accordingly.
So again, no complaints here. Just incredible thankful for all the possibilities in this great piece of kit and gratitude for the education in the way real amps work.

 

[IronSean]

Everyone here is asking for a switch that jumps between two values, when what we already have are knobs with fine grained control. People want to be able to "authentically" swap from 6L6 to EL34, but the Axe actually gives us much more control. we can adjust the tubes, and the transformer match, and a dozen other things we can't on an amp. And the other thing is we can a lot more control this way. In a real amp you can swap from EL34 or 6L6, and see which of two sounds you prefer. On the Axe, you can see which tube you prefer, and which transformer mismatch you prefer separately. And fine tune it to taste. Wish you could just swap half way to el34? or go to a super el34 that's twice as el34ey? Well you can.

"Automatically" doing it is also a can of worms. What if you already adjusted the transformer match then you adjust your tubes after? Does it go to the stock setting? Does it try and find a relative setting based on the new starting value?

And the other thing is that this would be a lot of extra work to include in the firmware and calculate. Some of the values needed might even need to be measured from the amp again. This is because I assume the modelling gets to ignore a lot of real values because they don't actually affect the sound. What affects the sound is the transformer match ratio. So the models can skip a lot of details and just use the transformer match to determine the final sound. This is good because it means the Axe can do it's modelling in real time with almost no latency and you can use it to play live. And you can adjust the ratio if you want it to be different.

So I think Joe creating an online app is a great solution. It will help calculate these values for people who really want to get the authentic "I switched the tube type switch on my dual rectifier" sound. And then, ideally, they can keep tweaking to where it sounds best afterwards anyway because they aren't constrained by the available power supply. And people who say "I want to switch tubes but it doesn't sound right" we can just start telling them "What you really want is to adjust transformer match. Turn it down to get more el34-ey, and up to get more 6L6-ey, and adjust to taste. Because why would you adjust it to 0.6 for authenticity when 0.7 sounds better?

 

[Smilzo]

Yes, you can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

I wish to blow virtual tubes!!
Seriously, I expect virtual circuit to retain the best of analog, and discharge the bad. Dissipation is a limit in a real tube, not virtual (well, it may sound like crap...).

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you.

Very true.

Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps.

I think most user don't want to learn how to set each parameters. They want "a brighter sound", "more djent", "Chewy middle", "more attack and responce", "better compression and string separation"... some AI to adjust a complex set of parameters! Way beyond the topic (or not?)...

Frankly all this compalining about something you have far more control over sounds entitled and whiny.

Just wishing.

 

[xarkon]

Yes, you can only use the transconductance values when changing between tubes with roughly the same maximum power dissipation. It doesn't work if you want to change a 6L6 to an EL84.

I know everyone wants this to work like a real amp but it's simply not going to happen. Some amps let you swap between EL34s and 6L6s and change bias accordingly. The problem is the Axe-Fx III lets you change between all the possible tube types. If you were to put an EL84 into an amp designed for EL34s it would sound terrible (and also destroy the EL84). A pair of EL84s wants to see upwards of 8K plate-to-plate. A pair of EL34s wants to see around 3.2K. If you put the EL84s in the amp the transformer would be extremely undermatched. It would also exceed the SOA of the tube and destroy it. In the Axe-Fx III the virtual tube wouldn't be destroyed but it would sound terrible and people would complain it doesn't sound right.

Those amps where you can use different power tubes don't swap the transformer. They just rebias the tubes. If the transformer turns ratio is optimized for 6L6s installing EL34s will cause the transformer to be slightly undermatched which is the primary reason the tone changes. Conversely if the transformer is optimized for EL34s installing 6L6s will cause it to be overmatched.

You have far more control over the power tube response with the Axe-Fx. Rather than complaining that swapping power tubes doesn't work exactly the same learn to use the fantastic power available to you. Learn to hear the difference changing the Transformer Matching and/or Speaker Impedance makes. These are controls you'll never find on a real amp. Changing the matching on a real amp involves removing the transformer and installing a new one. If you want fine gradation in matching you'd need something with many taps.

Frankly all this compalining about something you have far more control over sounds entitled and whiny.

This should be stickied in the tech notes.

 

[greiswig]

Everyone here is asking for a switch that jumps between two values, when what we already have are knobs with fine grained control. People want to be able to "authentically" swap from 6L6 to EL34, but the Axe actually gives us much more control. we can adjust the tubes, and the transformer match, and a dozen other things we can't on an amp. And the other thing is we can a lot more control this way. (SNIP)

IDK. Everyone is entitled to their opinion. What I put in the wish list would not negate the things that you describe here. It would just change the values for those same parameters in a way that better reflects what would actually happen.

Having a spreadsheet of values for transformer mismatch and impedance is fine, and I'd make use of it. It just seems like the equivalent of making people use their calculator to sum columns in Excel.

 

[reclavea]

No complaining and whining here.
Just stating what I found.

There is a hint of what seems like whiny in most of the posts altogether ....but I would say it’s not whiny ...just us trying to delve more into this great machine and it’s capabilities with its real world counter parts!

Who knows what lies in store for what we always wonder “How can it get any better?”

And

“Never say Never?”

 

[sprint]

There is a hint of what seems like whiny in most of the posts altogether ....but I would say it’s not whiny ...just us trying to delve more into this great machine and it’s capabilities with its real world counter parts!

Who knows what lies in store for what we always wonder “How can it get any better?”

And

“Never say Never?”

I confess - I was whining - waa waaa waa - I don't know how to do a virtual tube swap - waaaaaa

 

[mr_fender]

Personally I feel like this is one of those things that people want to mess with simply because it is there. How many users of real amps ever rely on changing tube types to get their sound? Mesa amps make switching easier with their dual fixed bias settings, but honestly the difference between EL34s and 6L6s in many of their amps was always quite subtle to me. There's a million other ways to shape and tweak the sound that are not only easier but more effective. Swapping tube types is pretty low on my list of parameters to adjust when creating a tone. If I need an "EL84 sound" or a "6V6 sound", I'll pull up an amp that uses them, not try to shoehorn them into something that doesn't.

You might eventually be able to put 24" dual wheels on a Honda Civic if you try hard enough, but it will never make it a dump truck.

 

[George Estremera]

Personally I feel like this is one of those things that people want to mess with simply because it is there. How many users of real amps ever rely on changing tube types to get their sound? Mesa amps make switching easier with their dual fixed bias settings, but honestly the difference between EL34s and 6L6s in many of their amps was always quite subtle to me. There's a million other ways to shape and tweak the sound that are not only easier but more effective. Swapping tube types is pretty low on my list of parameters to adjust when creating a tone. If I need an "EL84 sound" or a "6V6 sound", I'll pull up an amp that uses them, not try to shoehorn them into something that doesn't.

You might eventually be able to put 24" dual wheels on a Honda Civic if you try hard enough, but it will never make it a dump truck.

This is literally why I asked, initially. I had a Mesa Boogie TC-100 that came stock with EL-34's and I switched them out to 6L6's. There was a marked difference in that scenario. I expected the same in this case, but I have since been schooled quite a bit on this topic. Reading responses from those in the know has really helped me gain a better understanding (while not fully) of how tube changes actually work. I greatly appreciate all of the feedback this topic has gotten

 

[Joe Bfstplk]

Personally I feel like this is one of those things that people want to mess with simply because it is there. How many users of real amps ever rely on changing tube types to get their sound? Mesa amps make switching easier with their dual fixed bias settings, but honestly the difference between EL34s and 6L6s in many of their amps was always quite subtle to me. There's a million other ways to shape and tweak the sound that are not only easier but more effective. Swapping tube types is pretty low on my list of parameters to adjust when creating a tone. If I need an "EL84 sound" or a "6V6 sound", I'll pull up an amp that uses them, not try to shoehorn them into something that doesn't.

You might eventually be able to put 24" dual wheels on a Honda Civic if you try hard enough, but it will never make it a dump truck.

I build tube amps, and have done a fair amount of tube swapping/substitution over the past 30 years, frequently to keep gear running when the correct tube was unavailable back in the '90s, but also chasing a sound in my head on almost no budget. I'd grab an old tube amp at a hamfest or wherever, and mod away. I got an old Fisher X100C integrated hi-fi that had a bad OT in one channel, put a pair of Hammond 1620s in it, and redesigned its preamp for guitar, with a mono send, stereo return tube driven loop, and ran that for a number of years with my old Quadraverb GT, and later, Quadraverb 2. Made some great sounding amps that way. Eventually I started building from scratch.

Heck, I hear a fair amount of diff beteeen skinny EL34s and fat 6CA7s in my VZA Simone amp. Both sound different from the 7591s that I used to run.

I will admit to being an edge case among edge cases a lot of the time, but that's how you expand boundaries. Don't forget, the Marshall sound came from some bloody loony in England mostly copying a 5F6A Bassman circuit and swapping it over to KT66, and, later, EL34. The Boogie sound originated from modding Fenders. Vox copied a '50s Gibson schematic down to a T, even faithfully reproducing an error in the circuit, for its top boost tone stack, but set their output section up with EL84s after some early EL34 based amps.

"Without deviation from the norm, progress is impossible...." --Frank Zappa

 

[yyz67]

"Without deviation from the norm, progress is impossible...." --Frank Zappa

Woah, Dale thanks. That quote is probably Neil Peart's inspiration for a theme in Vital Signs, which I think is one of Rush's top lyrics describing the human condition (and also the fractal forum sometimes).

Unstable condition​

A symptom of life​

In mental and environmental change​

​

Atmospheric disturbance​

The feverish flux​

Of human interface​

And interchange​

​

The impulse is pure​

Sometimes our circuits get shorted​

By external interference​

​

Signals get crossed​

And the balance distorted​

By internal incoherence​

​

A tired mind become a shape-shifter​

Everybody need a mood lifter​

Everybody need reverse polarity​

​

Everybody got mixed feelings​

About the function and the form​

Everybody got to deviate​

From the norm​

​

An ounce of perception​

A pound of obscure​

Process information​

At half-speed​

​

Pause​

Rewind, replay​

Warm memory chip​

Random sample​

Hold the one you need​

​

Leave out the fiction​

The fact is​

This friction​

Will only be worn by persistence​

​

Leave out conditions​

Courageous convictions​

Will drag the dream into existence​

​

A tired mind become a shape-shifter​

Everybody need a soft filter​

Everybody need reverse polarity​

​

Everybody got mixed feelings​

About the function and the form​

Everybody got to elevate​

From the norm​

​

Everybody got mixed feelings​

Everybody got to deviate from the norm​

Everybody got to elevate from the norm​

Everybody got to escalate from the norm​

Everybody got to elevate​

Everybody got to elevate from the norm​

Everybody got to deviate from the norm​

 

[reclavea]

Personally I feel like this is one of those things that people want to mess with simply because it is there. How many users of real amps ever rely on changing tube types to get their sound? Mesa amps make switching easier with their dual fixed bias settings, but honestly the difference between EL34s and 6L6s in many of their amps was always quite subtle to me. There's a million other ways to shape and tweak the sound that are not only easier but more effective. Swapping tube types is pretty low on my list of parameters to adjust when creating a tone. If I need an "EL84 sound" or a "6V6 sound", I'll pull up an amp that uses them, not try to shoehorn them into something that doesn't.

You might eventually be able to put 24" dual wheels on a Honda Civic if you try hard enough, but it will never make it a dump truck.

As I posted earlier ...my experience was quite the opposite!

Swapping out the 6L6s for EL34 in my Mesa Mark III SIMUL-Class was a significant change in the sound!

Very bright ...much more presence!

Yet the drive characteristics seemed less ordered ...not sure why since the master settings are nominal. Maybe I was just hearing things? This thing was loud btw! I had a serious tough time maintaining balanced levels with the 3 modes.

I preferred the “smoother” sound of the 6L6s...for majority of my tones.

Wished at the time it was switchable though.

 

[Smilzo]

As I posted earlier ...my experience was quite the opposite!

Swapping out the 6L6s for EL34 in my Mesa Mark III SIMUL-Class was a significant change in the sound!

Changing tubes draws different current so voltage drift. The dissipation of a tube is different: different headroom, different perceived sound... so many variables...