FOXX: Tone Machine, BE Mods 2026

Updated Foxx Tone Machine layout on 0.15" vero.  This was inspired by the Aion mods - if you are unfamiliar with the Aion Vulcan, it's a Tone Machine with a modded EQ section (which is great) and an additional bypass option on one of the diodes - also a cool addition. 

I've tweaked a few values to suit my taste - this is not a stock Tone Machine.  

FOXX TONE MACHINE - BE 2026 V1

ADDITIONAL FOXX TONE MACHINE INFORMATION

Credit where credit is due - most of this information is from Aion build documents, which are excellent (go buy a kit, it will be easier than this...)

Transistors

The earlier Blue FTM used 2N3565 transistors with a hFE of around 230 to 245.   

The Red FTM used 2N3565 transistors with a hFE of around 450 - 550 

*I've also seen BC237B listed on the JD Sleep schematic from 2002.  

Treble Capacitor 

The earlier Blue used 3n3.   The Red used 2n7

Tone Control

Yes, it looks a bit like a Big Muff.   Can add a resistor after the treble cap to ground for BMP-like results.

The 4k7 resistor on the bass side of the treble control limits the range of the pot - jumper or remove for a tiny bit more range on the bass side.  

And of course, there is the mid-switch - basically adding more capacitance to the 3n3 treble cap, to boost mids.  I like a little bit of this action, but not too much.  15n is too much for me...  

Q3 bypass cap

Noted as 10uf on the schematic, measured at 22u, which does make a small difference to the bass response (more).  Basically, a 10u cap that is out of spec.

Additional Resistor

Red version had an extra 12k series resistor before the sustan pot, shaving a bit of level off.

Diodes

Use matched diodes in the octave section - originals used generic 1N34A diodes.  Matching just gives a better octave.   

Coupling Caps

Apart fromthe 100n on the input, the original used 10uf coupling caps.  They can be trimmed down to 1uf with no discernible difference.  

Optional Extras

The CBS Arbitier Doubler has a 10uf bypass cap on the emitter of Q1 - but is more gain here really needed?

Can add a 22u cap on the emitter of Q4 to bring the level up, as it can be a bit low.