Consistent octave up fuzz question?

[Esppse]

Hello,

I'd love to build an octave up fuzz like this.

https://m.youtube.com/watch%3Fv%3DSyxHHjRn_oo&ved=2ahUKEwjbhP69qM_fAhUGUt8KHdu8Ci4QwqsBMAJ6BAgLEAo&usg=AOvVaw0aYeyRWxvuMWu1y6m8PYAx

It seems that they managed to get the octave up consistent through the whole fretboard, that's amazing. I've never seen one that does that.

Does anyone have any recommendations on how to mod an existing build to respond to normal playing the way that octave pedal does? Or are there any other Vero layouts that do the same?

Thanks

[Mark Hammer]

Most octave-up fuzzes do exactly what they are told, and double the frequency of whatever they are fed.  HOWEVER, the challenge lies in making the doubling they provide result in an audible octave; that is a pronounced fundamental that is twice the input.  The reason why a great many octave-up fuzzes don't seem to result in a strong octave unless one is picking above the 7th or even 9th fret, on the unwound strings, is because the circuit doubles everything, including the stuff you're not interested in.  As a result, it's not until the string is rendered so stiff and uncompliant that the fundamental sticks out enough to be prominent in the doubling.  Thicker, shorter strings, will result in a better octave sound.  That's also why the received wisdom is to use the neck pickup, and roll back the guitar tone control; both reduce the harmonic content and allow the fundamental to stand out more prominently.  Finally, because guitar strings produce most of their harmonic content when you pick, and then settle down to produce mostly fundamental shortly thereafter, at a much lower level, many octave-up fuzzes will stick a back to back pair of diodes on the output to serve as a crude peak limiter, creating the impression/illusion of an octave that maintains a fairly constant level.

I find the most robust analog octave-up is the Foxx Tone Machine.  This seems to arise from its front end which emphasizes the frequency range where guitar-note fundamentals are most likely to be found.  I've also found that I prefer to use Schottky diodes for octave doubling, due to their much lower forward voltage.  But that's me.  Whatever you use, the goal is to provide for two equal-amplitude signals coming from the phase splitter.  The octave is created in combining two equal-amplitude copies.

[pinkjimiphoton]

+1 on the foxx tone machine.

but

check out gus smalley's octave up sick box. tracks the whole neck, and more sheer balls than the foxx pedal. no transformers or unusual parts required. make sure your pots are grounded or it may oscillate to the point of total instability if ya breadboard it. tons of fun.

that said, i use a FTM on my live board for the rare times i need an octave up. it has a consistantly beefy octave that really cuts thru well. and enough output, where ya can feel the boost if ya need it, unlike many that seem quiet due to cancelling the fundie-mental

[Esppse]

Ah thanks for the recommendations, Ive got both built, very nice circuits, the sick box has a nice folding sound. The screech got me because it sounds so close to a synth sawtooth wave. I've been looking for that sound for a while, a very singing, rich upper harmonic sound.

[Mark Hammer]

Using Schottky diodes, I find I can get a clearly audible octave down to around the 4th fret, though stronger above the 7th.

Dino Tsiptsis  has advocated for inserting a small-value resistor between the clipping diodes and ground.  This retains the limiting aspect, without introducing unnecessary additional harmonic content from hard clipping.  One can improve this even a little more by sticking a cap to ground, in parallel with that, to roll off the fizz.