Transistorless Sound Synthesizer

Description

Thanks to a circuit by Patrick Flett, I have a idea to develop his Patrick Oscillator into a mini synthesizer. This circuit uses the same Led/Cds photo resistor pairs that I use for Light Logic and Patrick shared his circuit with me in late September 2020 when we met on You Tube.

As of now, this synth is Monophonic just to keep the circuit as simple as possible.

As with my more recent projects, this one does not use any transistors but it does perform quite well as it is. It even drives my headphones to a comfortable level so no extra amp is needed.

Goal is to make a patch panel along with switches and variable pots to make use of all possible subtle sound output combinations as well as make or modify a basic piano style keyboard of one or two octaves.

Project Logs

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Testing the Theremin effect and a LFO
Dr. Cockroach • a day ago • 0 comments

October 25, 2020 - Video of current tests of the LFO and perhaps make a Passive Optical Theremin
First test scale
Dr. Cockroach • 10/14/2020 at 22:09 • 2 comments

October 14, 2020 - First test scale using the very basic keyboard. I still need to add the sharp/flat keys but this taking shape.
Tuning and Keyboard Module
Dr. Cockroach • 10/14/2020 at 15:22 • 0 comments

October 14, 2020 - Starting the layout of the tuning pots and keyboard switches.
The Basic Circuit
Dr. Cockroach • 10/14/2020 at 10:53 • 0 comments

Here is the basic circuit I am using. Pardon my poor sketch ;-)
Switches for the keyboard
Dr. Cockroach • 10/13/2020 at 21:07 • 0 comments

October 13, 2020 - I found some very small switches in my junk box that will do for a small push button keyboard. Not ideal but good enough for testing. These were from a printer/copier that my landlord gave to me so why not make use of some of those parts. This will be a single octave from C2 through to C3 plus a extra key on the left for a knob controlled tone. Right now the oscillator has a hard time reaching C4 so going with the lower octave. Besides I love the deep rich sound this circuit has down there :-)
The perfect multi-turn pot ???
Dr. Cockroach • 10/13/2020 at 12:44 • 3 comments

October 13, 2020 - I have had this old TV tuner board in my junk box for about thirty years and I think these 20K pots will be of great use in the tuning of the keyboard part of this project. These pots take about 100 turns for full range. Very fine tuning indeed ;-)
How it sounds in the raw so far
Dr. Cockroach • 10/11/2020 at 18:53 • 0 comments

October 11, 2020

This is just a sample of the deep low sound from the Patrick Oscillator. Very low frequencies and sounds great.

View all 7 project logs

Discussions

Ken Yap wrote a day ago

Cool! You should make a few and start an ensemble. As they say, many hands make light work. 🤣

Are you sure? yes | no

Dr. Cockroach wrote a day ago

Now that would be cool :-)

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Dr. Cockroach wrote a day ago

Light work.... Ooooooooo

Are you sure? yes | no

Yann Guidon / YGDES wrote 2 days ago

Doctor, you did it again !
https://hackaday.com/2020/10/24/a-transistor-less-sound-synthesizer/

Are you sure? yes | no

Dr. Cockroach wrote a day ago

I guess so but in all fairness Patrick Flett invented the circuit, I just pounced on it as a possible passive synth sound machine :-)

Are you sure? yes | no

Hari Wiguna wrote 2 days ago

Patrick Flett explains how it works in this video:
https://www.youtube.com/watch?v=fYMWZ75iO8g

Are you sure? yes | no

Dr. Cockroach wrote a day ago

Yes, I am so glad that Patrick shared his circuit with me and now I am expanding on it to where it might actually be a very flexible synth.

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Dan Maloney wrote 10/14/2020 at 18:37

I'm struggling to understand how the oscillation happens. I thought it required amplification and a positive feedback loop. Going to have to dig into this one a bit more - thanks for the head-scratcher. Like the way it sounds, BTW.

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Dr. Cockroach wrote 10/14/2020 at 21:01

I am struggling with the concept myself. My led/CdS Logic is easy enough to follow but this circuit confounds me a bit ;-)

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Ken KD5ZXG wrote 10/15/2020 at 19:33

if not inverting, perhaps just a relaxation oscillator.

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mh-nexus wrote 10/14/2020 at 17:48

Hi, interesting project.

I assume you meant this Patrick Flett: https://www.youtube.com/channel/UCdY0rnioc1twUgD6JwpuXvg

Maybe saying a bit more than providing a schematic would help to better understand how you want to make a synthesizer. Or do you just aim at making some sine wave sounds?

Are you sure? yes | no

Dr. Cockroach wrote 10/14/2020 at 21:00

Yup, same person, he found my Light Logic videos and we have exchanged some ideas and he sent me his schematic. This is my first real attempt at a synthesizer of any kind and this is the start of a very interesting build if I can maintain the transistorless aspect of it. The very simple keyboard is now working and tuned. I will post as I learn more and develop this project

Are you sure? yes | no

Dr. Cockroach wrote 10/14/2020 at 21:08

I would like to add loops and feedback as well as filtering but that will still be a step by step adventure for me :-)

Are you sure? yes | no

Transistorless Sound Synthesizer

Description

Project Logs

Collapse logs

Testing the Theremin effect and a LFO

First test scale

Tuning and Keyboard Module

The Basic Circuit

Switches for the keyboard

The perfect multi-turn pot ???

How it sounds in the raw so far

Discussions

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