Is this Insane?

[nelson]

For a Fuzz Pedal I mean.

I posted an older version of this a while back. My laptop hard drive moofed out I lost the files. So, I have decided to revisit the idea.

http://electroconducive.googlepages.com/CVGlitchshifterV1.2.pdf


So, you have the front end of the blue box feeding a PLL, in the loop you have a 555 set up as a variable frequency divider. That should equal variable pitch shift upwards. Now, what the 555 divides by and therefore increases the pitch by is controlled by Q1 and Q2 set up as a variable resistor, the frequency division is a product of the time constant of C11, R12 + Q1, when the cap is 2/3rds charged it instructs the 555 to trigger at the next pulse from the output of the VCO. Altering this time constant alters the frequency division.

This is controlled by one of two voltages: The LFO or the sequenced voltage coming out of the 4017. So, in theory, heavy square wave pitch shift and Arpeggiation should be possible.

The 4046 has a variable tracking control (Glitch) that will also trigger the internal VCO to start pumping out a frequency determined by the OSC pot. So, it could get pretty noisy and crazy. To ensure that the arpeggiation/pitch shift doesn't happen till you play I've employed a Jfet based gate on the LFO feeding the 4017 and to ensure that you don't get oscillation from the 4046 VCO when not playing I'll probably hook up the inverted gate signal to the Inhibit pin of the 4046. It's still very much an idea. I'm suffering a bit from feature creep on this one.

Conceivably you could hook up any CV to this and vary the pitch of the squared signal.

I guess I'm posting waiting for someone more knowledgable to tell me it'll never work and that I'm insane.

[R.G.]

You're not insane; at least not provably from this info! 

That info seems to hold together as far as you've presented it. The 4046 will indeed lock onto any signal in it's VCO range when used with phase comparator II, and a divider in the feedback loop will indeed put out a multiple of the lock frequency. The 555 does act as a frequency divider when set up properly. The only part that may be tricky is ensuring that the 555 divder is working like you want.

[StephenGiles]

Not half as insane - it seems as my Space Filter

[nelson]

You're not insane; at least not provably from this info! 

That info seems to hold together as far as you've presented it. The 4046 will indeed lock onto any signal in it's VCO range when used with phase comparator II, and a divider in the feedback loop will indeed put out a multiple of the lock frequency. The 555 does act as a frequency divider when set up properly. The only part that may be tricky is ensuring that the 555 divder is working like you want.

Yay! I think I may put this on a certificate, just incase I get sectioned.

About the 555; I'm sure you're holding back. Do you have any advice regarding utilising it to divide the frequency range in question?

[earthtonesaudio]

Wow, Nelson.  That is damn impressive.

I don't really understand all the features of the 4046, so I don't know if I can help, but I really like the "core idea" you have here, with the 4046 and 555 in some sort of crazy duel.

[Wales]

Insanely Great! The electronics are about twenty feet over my head (i just starting to step out of the copying phase and into the creating phase) but the idea of the pedal is great. i hope you get this working so you can sell me one, preferably cheap

[Transmogrifox]

Looks fun.  Have you done any transient simulations on it to see how it responds to nice sines and triangle waves?  You can also feed it a wav file.  There's actually quite a bit you can do to test and tune your theory in spice.

[nelson]

Looks fun.  Have you done any transient simulations on it to see how it responds to nice sines and triangle waves?  You can also feed it a wav file.  There's actually quite a bit you can do to test and tune your theory in spice.

I'm just picking up spice just now. I've not done any sims yet, I have had bits of it on the breadboard. I need to get to grips with Spice, I'm sure it would save me a lot of time.

[MoltenVoltage]

It just so happens I made a PLL-based distortion last week and got some pretty crazy sounds out of it (controlled by MV-52 tap chip).

It made some unique square wave distortion at times, and at other times it sounded like a sitar with all sorts of weird overtones.

At certain settings (I was randomly putting the signal into different pins and the clock control to other pins), the guitar frequency would change the output frequency of the square wave proportionally and I got some crazy deep bass (2 octave down) sounds, but they would only track for about half an octave.  It worked even better with a simple transistor pre-amp for the guitar input signal.

After a while it just gave me a brain bruise, so I tore it apart.

I think there is lots of potential in using a PLL for distortion and other strange harmonic generation if you are willing to suffer for your art!

I highly recommend using an oscilloscope to really see whats happening.

[MannequinRaces]

I'm too much of a newbie to understand the theory, but the idea sounds awesome!

[Taylor]

I'm curious if you ever built this up or got anywhere further with it. Very intriguing indeed.

[reubster]

After a while it just gave me a brain bruise,

Surely there is a market out there for that!

[mr.adambeck]

Did this ever get finalized?  Any sound clips?  Anything?  It sounds like such an interesting idea!

[joeloek]

wow this sounds freakin epic!
also:

Looks fun.  Have you done any transient simulations on it to see how it responds to nice sines and triangle waves?  You can also feed it a wav file.  There's actually quite a bit you can do to test and tune your theory in spice.

what software would you use for this?^^^^

[tref_h]

Spice.  http://en.wikipedia.org/wiki/SPICE

It's an old friend of anyone who's studied electronic engineering, certainly in the last 15 odd years...

[amptramp]

I can see the possibility of "spoofing" the phase detector in the 4046 where the harmonics become greater than the fundamental.  Since the pickups are at a fixed position, as you change frets, the pickup is at a varying proportional length of the active string.  This will cause various harmonics to be greater in amplitude at different fret positions.  Thus, you will get a "wolf note" where the frequency will go up or down an octave.  (And this does not take into account the effect of having six strings).  This corresponds to what MoltenVoltage has found.

Rather than use the comparator output (of IC1B) as the input to the 4046, you may want to add additional filtering ahead of this output for the summing function and the input of the 4046.  If you play one string at a time, this could be made to work, but with six strings, you may have to use a pickup with six outputs, one for each string and build six of these circuits with separate passbands for each.  Or you could use a graphic equalizer with one of these circuits per frequency, but that would not resolve multiple strings or fret position.