# Fender AB763 tone stack mods



## megatrav (Oct 30, 2020)

A friend of mine is building me a kit for a tube-driven preamp pedal based on an Alembic F2B (Fender AB763). Its just a single channel pedal and will have a bass, middle, and treble controls. I want to do some mods to the tone stack, including the ones in this pic






I am wanting to get slightly less bass and slightly more treble out of the tone stack overall. 
I was either going to replace the mid control with a switch to go between the .022 and .047 or just use the .022 as the mid cap and keep the mid control. Overall, I think it could be a little better suited for guitar.

Any suggestions would be appreciated.


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## Nostradoomus (Oct 30, 2020)

You could use a tone stack calculator such as this http://www.duncanamps.com/tsc/download.html to see if you can tweak it to your liking without modifying it.


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## megatrav (Oct 30, 2020)

Thanks!


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## HamishR (Nov 1, 2020)

You say you will have a bass/mid/treble tonestack but those are only bass and treble. In the Super Reverb and Twin Reverb (also AB763) the 6K8 resistor to ground is replaced by a midrange pot. It's easy to implement and the schematics are all online. I'm not a huge fan of the AB763 tonestack, especially for dirt sounds. If that's the sound you are chasing then that's cool but it may end up sounding a bit harsh.

There are loads of mods for these tonestacks. To get a fuller sound you can lower the value of the slope resistor (the 100K) and to get less bass boominess use a .022µF or .047µF for the bass cap.  Try a 500pF silver mica treble cap.


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## Dan0h (Nov 1, 2020)

Nostradoomus said:


> You could use a tone stack calculator such as this http://www.duncanamps.com/tsc/download.html to see if you can tweak it to your liking without modifying it.


Dude, this looks amazing going to download it today.


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## Dan0h (Nov 1, 2020)

Nostradoomus said:


> You could use a tone stack calculator such as this http://www.duncanamps.com/tsc/download.html to see if you can tweak it to your liking without modifying it.


This is what I’ve been looking for. This is the single best learning resource I’ve seen, in relation to how changing components changes the actual sound response and what the component placement does. Thank you so much again.


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