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Mark V Tone Match

Cbaf

New Member
Hey guys. I am doing some tone matches on my Mark V (Channel 3) Mark IV setting. Now my understanding is that we should get the amp to match as close as possible before capturing the match. I am using the USA Lead Brt+ and the results were incredible. The tone match curve was actually almost completely flat.

Now I want to match the same but with EL34s installed as the power tubes. So if I follow the same logic and the fact that the USA Lead Brt+ was modeled with 6L6s, what are the parameters I should change on the model to get it as close to my MV with EL34s? There are so many parameters I have never used so looking for some guidance. Thanks!
 

shredi knight

Power User
The most obvious one by far would be to change the "PWR Tube Type" parameter in the amp block's advanced page from "Tetrode" (6L6) to "Pentode" (EL34).
 

stm113

Experienced
Is that the actual function if the tetrode/pentode? I don't hear the big difference like I should if you actually swapped power tubes..


I'd love to get or hear that tone match
 

tomc3084

Experienced
Try using a sine sweep to do the tonematches, I hear this is the most accurate way. There is a tutorial around here for it. If you can get around to it, I would be forever grateful if you could match the Mark I mode with the thick switch and without it. I have been able to get all the tones from the Mark V in the Axe FX II, except for the Mark I mode.
 

FractalAudio

Administrator
Fractal Audio Systems
Moderator
Is that the actual function if the tetrode/pentode? I don't hear the big difference like I should if you actually swapped power tubes..


I'd love to get or hear that tone match
Changing the power tube between pentode and tetrode doesn't change the sound in the same way actually changing tubes would because it only changes the distortion curves. It does not change the transconductance so the transformer matching is constant. When you put different power tubes in an amp the difference in tone isn't due to some inherent difference in the "sound" of the tubes. It's mainly due to the different transconductances. An EL34 has more than twice the transconductance of a 6L6. This means that the plate current will be twice as great for a given grid voltage. This makes EL34s sound "more midrangey" and 6L6s sound "tighter" or "fuller". The truth is that if you bias them correctly and compensate for the difference in transconductance you will hear very little difference. Unfortunately you can't compensate for the transconductance easily in a real amp without changing the gain of the phase inverter and/or putting in a different output transformer.

I don't know what happens in a Mark V when you select EL34s as the tube type. I'm assuming it changes the bias but it might change other things. Fortunately you don't really need to worry about all that. Tone Matching will take care of that stuff. People underestimate what Tone Matching does. Yes, it is "just" EQ but that is 99% of what you hear in an amp like that. All of the distortion comes from the preamp so changing power tubes is just altering the output frequency response. I'd be surprised if the curve deviated that much from flat.
 

InsideOut

Power User
Changing the power tube between pentode and tetrode doesn't change the sound in the same way actually changing tubes would because it only changes the distortion curves. It does not change the transconductance so the transformer matching is constant. When you put different power tubes in an amp the difference in tone isn't due to some inherent difference in the "sound" of the tubes. It's mainly due to the different transconductances. An EL34 has more than twice the transconductance of a 6L6. This means that the plate current will be twice as great for a given grid voltage. This makes EL34s sound "more midrangey" and 6L6s sound "tighter" or "fuller". The truth is that if you bias them correctly and compensate for the difference in transconductance you will hear very little difference. Unfortunately you can't compensate for the transconductance easily in a real amp without changing the gain of the phase inverter and/or putting in a different output transformer.

I don't know what happens in a Mark V when you select EL34s as the tube type. I'm assuming it changes the bias but it might change other things. Fortunately you don't really need to worry about all that. Tone Matching will take care of that stuff. People underestimate what Tone Matching does. Yes, it is "just" EQ but that is 99% of what you hear in an amp like that. All of the distortion comes from the preamp so changing power tubes is just altering the output frequency response. I'd be surprised if the curve deviated that much from flat.
I absolutely LOVE the educational posts from Cliff. Thank you sir, and please keep them coming 8) I've learned so much more about tube amps now that I don't use them anymore :lol
 
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