Fulltone Ultimate Octave

[Petethefuzz]

In it's core it's a slightly modded Foxx Tonemachine I think. I really dig the switch that alters the tone though and the external foot switch for the octave. I know the schematic is well known but I haven't yet tried to build any thing that wasn't done on a pcb

 

[ICTRock]

Fuzzy Fox Ultimate Octave Recipe taken from the really old schematic over at musikding https://ibb.co/h9h3g5z :
R1 - add 10p in parallel
C1 - 47n
Q1-Q4 - 2SC828
C2 - 47n
C5 - add 10K series resistor between C5 and Sustain lug 3 (or whichever has continuity with C5), I usually just remove the pot leg and replace with resistor.
Sustain - 100KB with 100K parallel between lugs 2 and 3 ... you could just leave this 50K tbh
C9 replace with switch(DPDT ON/ON) switching between 15n and 1n
C10 - 100n
Tone - 100KB
Volume - 100KB

If you want the octave to be a stomp, use half a DPDT stomp switch instead of the toggle, using the other half for the additional LED switching. I'd use schottky diodes for the octave generation (D1. D4) and germanium for the hard clipper/limiter section of the circuit (d2,d3) ... and honestly, you're not going to tell the difference between 2sc828 and 2n5088 in this circuit until drastic changes are made in the clipping section.

The 10K resistor between C5 and the Sustain pot means the Ultimate Octave does not generate as much fuzz as the original foxx tone machine. I feel like that needs to be pointed out in case you were looking for ways to simplify this build.

 

[Petethefuzz]

Fuzzy Fox Ultimate Octave Recipe taken from the really old schematic over at musikding https://ibb.co/h9h3g5z :
R1 - add 10p in parallel
C1 - 47n
Q1-Q4 - 2SC828
C2 - 47n
C5 - add 10K series resistor between C5 and Sustain lug 3 (or whichever has continuity with C5), I usually just remove the pot leg and replace with resistor.
Sustain - 100KB with 100K parallel between lugs 2 and 3 ... you could just leave this 50K tbh
C9 replace with switch(DPDT ON/ON) switching between 15n and 1n
C10 - 100n
Tone - 100KB
Volume - 100KB

If you want the octave to be a stomp, use half a DPDT stomp switch instead of the toggle, using the other half for the additional LED switching. I'd use schottky diodes for the octave generation (D1. D4) and germanium for the hard clipper/limiter section of the circuit (d2,d3) ... and honestly, you're not going to tell the difference between 2sc828 and 2n5088 in this circuit until drastic changes are made in the clipping section.

The 10K resistor between C5 and the Sustain pot means the Ultimate Octave does not generate as much fuzz as the original foxx tone machine. I feel like that needs to be pointed out in case you were looking for ways to simplify this build.

Thank you so much - Maybe it's time I get my feet wet when it comes to not just building kits from musikding.de They have there own take on the Foxx and it looks like a good starting point though. Fuzzdog has a cool kit of the Ultimate Octave but since brexit it's quite expensive to shop from the UK when you live in Denmark (EU) like me.