Guitar Synth Pedal

Statement of Purpose

I’m going to build a guitar synthesizer/distortion pedal using a 4046 Phase Locked Loop.

Background Research

I’ve been wanting to do an effects pedal like this for a while (the ideas been brewing in my head for over a year, I’ve drawn out schematics multiple times but not gotten to actually building it)., it’s loosely based on the oscillator design for voice cards for an analog polyphonic synthesizer I designed in high school, and most of the design is original. That being said, it’s basically switchable between a phase locked loop and class D amplifier with waveshaping capabilities

Block Diagram / Flow Chart

System Overview

It’s really complicated, but basically we have two modes:
First has a phased lock loop oscillator attached to the guitar signal. This signal is shaped in a few ways, including comparators, and mixers, and then is put out.

The second uses the VCO in a high-frequency mode (60k-100khz), outputting a variable waveform. This signal is then put into a comparator with the original signal and lowpass filtered to get rid of frequencies above 20khz. If the output of the VCO is a saw or triangle wave, this will exactly replicate the signal. But, if the output of the vco is a variable waveform, this will cause waveshaping of the original signal.

Parts

Provide a list of parts that you may need for your project. You should include details such as the quantity, model number, purpose, vendor, and price (excluding taxes and shipping) for each part. This list may change as you work on your project. 

Parts list:

4046 PLL chip (already own)

Op amps (hopefully no more than 2 quad op amps, and an extra dual op amp for buffer)

Smattering of resistors, diodes and capacitors

3spst switch (already have)

Enclosure

Potentiometers for knobs.

¼ inch jacks (already have)

Dual power supply converter (from 9v battery, maybe)

I’m not sure of the total price, but besides the Pots, we’re talking under 20 dollars. The pots could get expensive, but I can’t imagine it being that bad.

Possible Challenges

Please list some of the challenges that your group foresee in working on your project.

Phase locked loops are kinda finicky. I have a circuit that’s pretty reliable from my previous project, but I’m going to have to troubleshoot it a lot more considering we’re using a guitar signal. 

Shifting between the two modes is going to be interesting, I'll probably have to use dual pots, it'll be a challenge to get the values to line up.

Getting a reliable pulse width square wave out of the guitar signal will be hard. I'm probably going to use a really strong LPF, and a schmitt trigger.

References

List all references you used in your proposal. This is important, you do not want to be blamed for plagiarism. IEEE citation format is highly recommended. You can use citethisforme.com's IEEE citation generator to painlessly generate your references in this style.

I don’t have any specific sources, this has all been brewing in my head for over a year and a half. But here are some sources to give a general impression of what I’m trying to do. I’ve never really seen anything like what I’m doing now done before. 

[1]"X-4046 VCO", Birthofasynth.com, 2022. [Online]. Available: https://www.birthofasynth.com/Thomas_Henry/Pages/X-4046.html. [Accessed: 19- Feb- 2022]

https://www.ti.com/lit/ds/symlink/cd4046b.pdf?ts=1645171764659&ref_url=https%253A%252F%252Fwww.google.com%252F