FOXX: Tone Machine

One of my favourites - the Foxx Tone Machine.  I've posted a couple of layouts, one stock, the other is the Aion FX Vulcan.  The Aion FX mods make the Foxx even better - I prefer it with the mid switch mod.  

The mid switch mod really gives this circuit a lot more range.  The diode switch is also interesting - with the octave off, one diode remains in the signal path.  The diode switch bypasses this diode for a slightly different sound.

Apart from the 10uf from Q3 to ground, all other capacitors can be replaced with 1uf electrolytic or poly caps.  Might save some space, or maybe you prefer polys over electrolytic in the signal path.

My only disappointment with making the Foxx, is that I can't replicate the incredibly seventies looking velour stompbox enclosure.

FOXX TONE MACHINE - VERO LAYOUTS

Or something a little more traditional in terms of size and where the wires leave the board.  I could have made the board smaller, but I was going for something with plenty of room around components.  

FOXX TONE MACHINE / AION FX VULCAN - VERO LAYOUT

Read the build docs on Aion FX for the Vulcan to find out more.

AION VULCAN - TONE MOD

Here's what the responses look like on LTspice (distortion mode), with the tone control set to 50%.  

Increasing the 15n cap to 47n flattens the scoop, and the 1n and 2.2n can also go up a size if you prefer a flatter mid-range (not shown in responses below)

This is with the additional 22k resistor

Without the additional 22k resistor

FOXX TONE MACHINE - LTSPICE

Stock Tone Machine, no mods as a reference

Output in red, plus the response on either side of the tone pot on the distortion setting.  Mellow is blue, and bride is green.

Same again on the octave setting

STOCK FOXX SCHEMATIC

FOXX ON THE SCOPE

This is straight from the first boost stage