These are my build notes for the nonlinear circuits Sandy Freckle module.
It's a eurorack module.
It's main use is as sound source .... a burp/fart generator .
The design was based on a old 1980's circuit from a Australian company called Dick Smith.
I loved the old ads ... the slogan went something like... "they don't call me the electronic dick for nothing".
(Probably wouldn't get away with that today.)
I might still have some of those old books packed away somewhere.
If youre interested in exploring ancient history the link to those old books are here:
I think they are still useful today. There is a synth project at the end of book 3.
Anyway, this circuit uses transistors to build multivibrators.
They are loosely connected (via resistors) causing them to influence one another.
They run at different speeds creating different pitches.
Then they get mixed up.
The 3 pots adjust the frequencies. I don't think they sounds much like farts.
More like deep base drones .... rather unpredictable and hard to repeat.
You can feed gates & envelopes to trigger the module.
The last video below uses a ramp LFO as a trigger
You can think of this module as a random pulse generator.
If you feed it audio rate signals and it becomes a waveshaper/distortion module.
The name of the module comes from an old Australian comedy show called "Kath & Kim"
Sandy Freckle was a villain played by actor Rock Hampton. Maybe Villain is too strong a word.... bumbling crook?
Links
+ Wiki
+ BOM..
You'll need 6 transistors in the build ... BC 847
and one op-amp TL072
The rest of the components are standard caps & resistors.
Feel free to use different values for C1, C2 & C3
I'm using these values:
C1 100n
C2 10u
C3 1u
I'm using a 10R resistor for power protection. It's the worst option as it only protects your module by burning up if you plug the power in backwards .... but I don't have any rectifiers.
So just don't plug it in back to front OK.
For the RL resistor I'm using a 1K .
Just experiment.... Andrew recommends 2.2k ... but it all depends on your LED's brightness.
The LED needs to be really bright to shine through the panel.
When you're putting on the resistors be careful not to mix up the 100k with the 100R
Caps next
The pots are all 1M
Jacks
The LED next
When you run it for the first time without any inputs you should be able to hear a deep drone from the output. You can also see the LED flashing in sync with your drone. (sorry, no sound in the video)
The second video below has a LFO plugged into the input of sandy.
You get the idea.
It's done.
A nice easy build to start off 2024
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You can find more NLC builds here.
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