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Wish Preamp tube mismatch


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Mismatching the preamp tubes (creating slight variations in their behavior) will still effect the tone in the intended way, regardless of their function. If each virtual tube is a mathematical copy of the others, they all are doing the same thing in the same way. If there are slight deviations between each of the virtual tubes, they will each do their thing a little differently than the others, the more dissimilar they each are, the more audible effect it would have on the tone.

I might be misunderstanding the power tube mismatch parameter to be doing something it's not.

If the power tube mismatch parameter is only effecting the difference between the push and pull tubes, I might clarify the original post to state "Add the ability to simulate real-world dissimilarity between the virtual preamp tubes". Whatever the power tube mismatch parameter does to the virtual power tubes to simulate dissimilarity, either individually or in pairs...that effect, albeit to a much lesser extent (equivalent to maybe +/- 0.30 of the current power tube mismatch parameter), applied to each of the virtual preamp tubes, as a group.

The various types of modeled preamp tube types all have their own signature behavior and character...even different manufacturer's model of the same tube construction being slightly different in sound and character from the same tube type from another manufacturer.

That same slight variation will also exist, to a much lesser extent, between the same tube type from the same manufacturer. That slight variation is what I'm interested in being able to adjust, in the same way an older set of JJ preamp tubes will sound slightly dissimilar to a brand new set of JJ preamp tubes. For the same intended purpose that guitarists will swap out various single preamp valves in an amp for different types and manufacturers, effectively mismatching their set of preamp tubes, to achieve some unspecified tonal destination.

I might be misunderstanding the term mismatch altogether, and might need to clarify the original post even further to state "The ability to simulate real-world variations in the virtual preamp tubes for a given selected preamp tube type". In order to simulate age, use, manufacturing tolerance variation, etc. (The difference between the "ideal" preamp tube type, and another modeled brand type... that slight difference, applied as a scalable random median value, to all of the tubes in the group of tubes of the chosen tube type.)

I hope my attempts at clarification have been successful.


Actually, this is a really interesting request. I wonder how much variations between tubes would affect tone?

It might be interesting to be able to control tube age as well.


I wonder how much variations between tubes would affect tone?
Variations between tubes mostly comes down to differences in transconductance. In a power amp, a transconductance mismatch can change the harmonic structure of a signal. But in preamps (and single-ended power amps), these variations mainly come down to changes in gain and bias point. We have those controls already.


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I'll try experimenting with bias excursion, I haven't played with that yet. If preamp tubes are self biased, and the only real difference you get between different types of preamp tubes is gain and bias point changes, I bet between preamp bias (last tube) and bias excursion (all preamp tubes) there are some more available sweet spots. However, my interest is in specifically where the virtual tubes are set at their zero point, as a group, and the adjustability of that zero point.

My main interest for the wish is to be able to adjust the zero/start point of where the preamp tubes (all of them) are set at their starting point, whether that means gain or bias or impedance or transconductance.

Adjusting power tube mismatch parameter just slightly away from zero makes such a blatant audible change, where zero feels very cold, and moving just off of zero adds an element of reality to the sound/feel that I had not yet ever heard. I'm interested in having that real-world variation ability applied to the preamp tubes as a group.

If the preamp bias parameter only adjusts the bias point of last valve, the other valves aren't accessible to adjust their bias/gain zero point, so other than the bias excursion parameter (which I would assume gets applied to the whole preamp section), the other valves are not user adjustable past their set zero point, save for the ability to pick the preamp tube type as a set.

I'm interested in being able to adjust the entire set of selected virtual preamp tubes as a whole, up or down, in a scalable equivalent to having a "cool" set of JJ 12AX7s, or a "hot" set of JJ 12AX7s, and the ability to mismatch the preamp tubes of the selected type, in scalable amounts, similar to the power tube mismatch parameter, so that increasing the value of mismatch separates the virtual preamp tubes from each other in slight amounts of gain/bias/transconductance, as you would find in measuring the properties of multiple preamp tubes of the same type from different manufacturers, or even from the same manufacturer.
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I like it, even if it could be very subtle.
I would prefer input level control for each stage, so that we can fine tune distortion and feel given a "modeled" preamp.

Light OT: the "ideal/cold/stiff" versus "real/warm/3D..." tone is intriguing... the ability to fine tune a patch in a simple way (i.e. "I want more bright tone, but with loose low end not boomy but crispy...") could lead us to A.I. (artificial intelligence, knowing what each technical parameters does to the sound and choose the best set for our needs).


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That is what Cliff does. Check the components reactions, and draws the models. What we could ask is some way to change our tone, like a race driver could ask for a switch from "rounder" to "stiffer" behavior...
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