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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Let the circuit bending/blending begin
Dr. Cockroach • 11/23/2020 at 15:48 • 0 comments

I have decided to begin blending the Patrick oscillator and other circuits to the keyboard. The circuits are mounted and just need the interconnects added.
Where is this heading????
Dr. Cockroach • 10/28/2020 at 21:20 • 0 comments

October 28, 2020 - I am at a bit of a crossroads with this project. I will continue to explore just how much I can expand the range of sounds with this oscillator but now I also want to build a multi voice drone similar to what Sam from Look Mum No Computer fame has made at https://www.lookmumnocomputer.com/
If you have a moment then check out his projects. All are Mad Good but I really love the Drone of his and I think I can make at least a 5 to 10 voice example. Check out his Megadrone https://www.lookmumnocomputer.com/projects#/1000-oscillator-megadrone
And if I make a batch of oscillators then I could have a basic and messy polyphonic system in its beginning stages.
Testing the Theremin effect and a LFO
Dr. Cockroach • 10/25/2020 at 13:01 • 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 • 5 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 9 project logs

Discussions

emel25396 wrote 05/08/2021 at 06:33

its looks interesting project and very similar to mine you can see here https://www.soundboxlab.com/ the similarities of my project.

Are you sure? yes | no

Yann Guidon / YGDES wrote 10/27/2020 at 03:00

I'd love to build a polyphonic one...

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Dr. Cockroach wrote 10/27/2020 at 10:42

Actually, I have already started on that. All I need for the single octave is one oscillator for each note. As long as I keep it simple XD

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Ken Yap wrote 10/25/2020 at 05:12

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

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Dr. Cockroach wrote 10/25/2020 at 09:43

Now that would be cool :-)

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Dr. Cockroach wrote 10/25/2020 at 09:44

Light work.... Ooooooooo

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Dr. Cockroach wrote 10/27/2020 at 10:42

Light Work, I love it :-)

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Yann Guidon / YGDES wrote 10/25/2020 at 00:50

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

Are you sure? yes | no

Dr. Cockroach wrote 10/25/2020 at 09:43

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

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Hari Wiguna wrote 10/24/2020 at 23:38

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

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Dr. Cockroach wrote 10/25/2020 at 09:38

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?

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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

Let the circuit bending/blending begin

Where is this heading????

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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