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Axe-Fx 3 Amp Block Valve Configurations?

neale dunham

Inspired
So I've been experimenting with different valve types within the amp block and even with headphones cant hear a lot of change I any in my tone when I select say EL34 as opposed to 6L6 output valves for example?

Is this normal, or has this section been reserved for Eric Johnson and those with Dog like hearing?

Are there specific amps where the effects are more prominent or do I have something set incorrectly?
 

slinky005

Forum Addict
So I've been experimenting with different valve types within the amp block and even with headphones cant hear a lot of change I any in my tone when I select say EL34 as opposed to 6L6 output valves for example?

Is this normal, or has this section been reserved for Eric Johnson and those with Dog like hearing?

Are there specific amps where the effects are more prominent or do I have something set incorrectly?
I agree.
The difference is so subtle I just don't go there for any adjustment.
 

Lilarcor

Inspired
In a nutshell: The differences you hear when you change the power amp tube type in a real amp are mostly due to output transformer mismatch and not to tube type itself. The Axe Fx changes the virtual output transformer values to match the tube type. That's why the differences are so subtle.
I proposed this to be changed or made an option some time ago but nothing has happened, yet. There are probably a lot of way more important things on Fractals agenda.
You can compensate by changing the transformer mismatch parameter manually.
 

neale dunham

Inspired
Hi lilarcor,

Can you explain further on this please?
You say that the differences that are heard in a real amp are due to transformer mismatch?
What is transformer mismatch exactly?
Also, I don't understand why, if you are able to hear transformer mismatch, then surely, as the term suggests, you should be aiming to "match" the transformer with the valve and therefore you should still be able to hear the difference between say a 6L6 based amp and a EL34 driven amp?
Confused.....?
If you match an output transformer using 6L6 valves I understand this will sound different to an El34 setup using a transformer optimised for these valves but why doesn't the Axe automatically simulate this change?

How do I change the settings to say run a Mesa Boogie in the amp block using a Marshall type transformer and EL34 valves for example?
 

Brownmatthall

Forum Addict
Another thing to consider is that the change is going to affect amps that rely on PA distortion much more than those relying on preamp distortion, could be a contributing factor to why you don't hear much of anything
 

unix-guy

Legend!
If you match an output transformer using 6L6 valves I understand this will sound different to an El34 setup using a transformer optimised for these valves but why doesn't the Axe automatically simulate this change?
The Axe Fx automatically adjusts the Transformer to match the tube type.
 

Lilarcor

Inspired
Hi lilarcor,

Can you explain further on this please?
You say that the differences that are heard in a real amp are due to transformer mismatch?
What is transformer mismatch exactly?
Also, I don't understand why, if you are able to hear transformer mismatch, then surely, as the term suggests, you should be aiming to "match" the transformer with the valve and therefore you should still be able to hear the difference between say a 6L6 based amp and a EL34 driven amp?
Confused.....?
If you match an output transformer using 6L6 valves I understand this will sound different to an El34 setup using a transformer optimised for these valves but why doesn't the Axe automatically simulate this change?

How do I change the settings to say run a Mesa Boogie in the amp block using a Marshall type transformer and EL34 valves for example?

Read the wiki page that Yek posted the link to. I merely provided a short summary. There is also a quite a long thread on this forum about the typical mismatch values for a few common tube type changes. Unfortunately I can't find it right now.
 

yyz67

Inspired
Also from the wiki "You can simulate changing power tubes in the Axe-Fx by simply increasing or decreasing the LF and HF resonance values."

Changing tube type, I do usually hear a slight difference. It's subtle (esp in clean amps which I tend to prefer), like a slight change in fullness or clarity or compression. To me the 300B tends to sound more different from the other tubes.

I agree that an 'authentic' tube mode would be cool just to play with, but understand this would probably require more internal settings to be stored for each tube type / amp in addition to a UI change.
 

200man

Veteran
Clif...from the wiki:
Well, the fact is that power tubes do NOT sound different.
So, they offer tube substitution capability, yet they are all normalized in the model to sound the same when changed...okay, got it. :)
 

yyz67

Inspired
Clif...from the wiki:
Well, the fact is that power tubes do NOT sound different.
So, they offer tube substitution capability, yet they are all normalized in the model to sound the same when changed...okay, got it. :)
Not exactly. Cliff's statement is taken a bit out of context and the conclusion that they will sound identical is not correct.

It is "the circuit context" of a tube that affects its affect on sound. He also says "There's a little more to it as the output transformer plays a role as well and 6L6 power amps typically have a slightly higher impedance ratio. There's also different operating voltages and bias points but I'm trying to keep this simple."

Cliff "normalizes" (optimizes) )certain aspects (bias, transductance...) but that doesn't mean there won't a residual discernible (if slight) difference depending on all these factors, even if largely adjusted for.
 

JCBitB

Inspired
If you're going for cranked power amp stuff it can be more impactful. Still subtle tho, and for me its often more of a difference in feel than a change in eq curve.
 

200man

Veteran
Not exactly. Cliff's statement is taken a bit out of context and the conclusion that they will sound identical is not correct.

It is "the circuit context" of a tube that affects its affect on sound. He also says "There's a little more to it as the output transformer plays a role as well and 6L6 power amps typically have a slightly higher impedance ratio. There's also different operating voltages and bias points but I'm trying to keep this simple."

Cliff "normalizes" (optimizes) )certain aspects (bias, transductance...) but that doesn't mean there won't a residual discernible (if slight) difference depending on all these factors, even if largely adjusted for.
Not taking it out of context...I’ve read the entire thing...but no worries mate...

The point I was trying to make is simply if you substitute tubes, changes to parameters are occurring which has a basic effect of normalizing the sound. I’m not saying its perfectly normalized. So in effect if you want to play with tubes....probably...not sure...grab an amp at its default settings...copy the relevant parameters before you flip tubes. Then “restore” the parameters. If this is the case then for those old tube guys who got certain sounds in certain amps with certain tubes...they could simulate that effect. Otherwise, honestly, what would even be the point of offering tube substitution?
 

yyz67

Inspired
Not taking it out of context...I’ve read the entire thing...but no worries mate...
Sorry, I didn't need to say that.

Otherwise, honestly, what would even be the point of offering tube substitution?
I think only Cliff could answer. Maybe it was a user request? I seem to recall earlier Axes might have had a set of a few ideal tubes that expanded over time. I do hear differences though, sometimes enough for me to prefer one over another.

So in effect if you want to play with tubes....probably...not sure...grab an amp at its default settings...copy the relevant parameters before you flip tubes. Then “restore” the parameters. If this is the case then for those old tube guys who got certain sounds in certain amps with certain tubes...they could simulate that effect.
That would be cool tho I don't think this works because many of those settings are still internal, thus no way to grab the parameters? In addition for simplicity/flexibility of the internal amp algorithm design, some of them might already be "normalized" or scaled to a standard (or ratios) rather than using absolute voltages, etc. But this is merely a guess (coming from writing data processing algorithms myself).
 

Joe Bfstplk

Inspired
I proposed this to be changed or made an option some time ago but nothing has happened, yet. There are probably a lot of way more important things on Fractals agenda.
You can compensate by changing the transformer mismatch parameter manually.
A "cab impedance mismatch" selector allowing load mismatches from 1/2 to 2/1 with a number of steps between (2/3, 4/3, 3/2, for example) would be nifty. Amps respond differently when loaded with non-optimal speaker loads. Part of the tweed Bandmaster sound is the 2.667 ohm load on a 4 ohm output tap (a 2/3 load). Play it through a 4 ohm load and it sounds more like a Super. The circuits are almost identical, so the difference comes from the PS, and fro. OT loading....
 

Brownmatthall

Forum Addict
A "cab impedance mismatch" selector allowing load mismatches from 1/2 to 2/1 with a number of steps between (2/3, 4/3, 3/2, for example) would be nifty. Amps respond differently when loaded with non-optimal speaker loads. Part of the tweed Bandmaster sound is the 2.667 ohm load on a 4 ohm output tap (a 2/3 load). Play it through a 4 ohm load and it sounds more like a Super. The circuits are almost identical, so the difference comes from the PS, and fro. OT loading....
https://forum.fractalaudio.com/threads/the-secret-weapon-transformer-match.98527/
 

Raab90

Inspired
There's a Wish List sub-forum for all types of requests in case you'd like to see a non-optimized substitution feature.
 
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