Salen-Key VCF

This is a voltage controlled low pass filter with three control voltage inputs and three audio inputs.  Designed for 9V but could be higher.  This design has not been tested so use at your own risk.

Chaotic Circuits

Ian Fritz has a number of chaotic circuits on his page that look really interesting.  I thought I would start with one of the simpler ones.  This is my drawing of the Driven Damped Well chaotic oscillator.  Unfortunately this does not seem to make any sound when I power it on so I need to trouble shoot it.

Update: I did some trouble shooting but it still does not behave as expected. (chaotically) it seems to be passing the original sound to the output.  I am monitoring the NL output so I think I will switch over to the X output.

Update 2: I did more trouble shooting and switched the output to X and now it does indeed behave chaotically although in a not very usable fashion at the moment.  One thing I love about chaotic systems is that they depend on prior initial conditions.  So as you turn the knobs the circuit may not be making any sound, then you pass a point and here a blip, as you tweak around the blip you gradually bring it into oscillation.  Suddenly the oscillation goes away and you get silence again.

I have been feeding the output of an Atari Punk Console in to drive this circuit.  At some settings it has been making some overtones and clicks but they are difficult to find.

Current DIY Projects

 These are some pictures of some current DIY synthesizer projects.  This first one is a 10 step sequencer with a 555 clock.  I used different colored LEDs for each step (not sure if this will mess up functionality yet).

The next one is my DACPOD.  This will be mounted in a case and combines a simple resonant VCF with an Atari Punk Console and my blinking light circuit to give it two flashing LEDs.

 This circuit is supposedly a snare drum but it needs a couple of capacitors and a transistor yet.

This is a Rossler Attractor chaotic oscillator circuit.  Should have put some caps on the outputs for this one.

This circuit combines (left to right) a control voltage mixer, a voltage controlled resonant low pass filter, and a NANDsynth oscillator as well as blinking LEDs along the top.  This circuit ended up as my Steam Drone box.

MFOS Alien Screamer

Ray Wilson has come out with a new circuit the MFOS Alien Screamer:

I really like the sound of this thing and possibly more importantly I like how such a complex sound can be generated by such a simple circuit.  Ray has done a great job of extracting the most functionality out of the fewest components here.  The only thing missing is an appropriate filter to go with it.  I have been working with a couple of VCFs including Ray's Odd Filter from the Weird Sound Generator but I think for this one a LM13700 filter is more appropriate.

Atari Punk Console

This is my layout for my Atari Punk Console.  This is about as compact as you can probably make this device without going to surface mount.  The + and - go to a switch to the battery.  The P+ supplies the positive voltage to the two pots (right side), the PP goes to the wiper of the Pitch Pot, the PM goes to the wiper of the Mod Pot, CvR provides a voltage to the two control voltage RTS 1/4 jacks and should connect to the ring of both jacks.  This will allow you to use an expression pedal to sweep pitch or mod.  Note the resistor presents too much current from flowing if you short out the connection.  The CvP goes to the tip of the pitch control voltage quarter inch, and the CvM goes to the tip of the mod control voltage quarter inch jack.  The output goes to the tip of the 1/4 right of an audio pot 10k-100k.  The wiper goes to the tip of quarter inch jack.  The sleeve of the jacks should all be connected together and grounded.

This design makes use of both modulation connections on the 556 chip so you can modulate pitch and wave shape.

This setup has the following additional components:

2 stereo 1/4 inch jacks for control voltage or expression pedal input
1 mono 1/4 inch jack for output
2 500k - 1M linear taper pots (either work) for pitch and wave form modulation
1 10k-100k audio taper pot (either should work) for volume
1 SPST toggle switch for on/off
1 battery clip or 9V supply connecter (or both)
1 case of some type, a lot of options here but I like the "Really Useful Box" series from Office Depot because they are easy to drill holes in.

Here is a video demonstration of this device:

You can use this to make a PCB.  You will have to scale to the correct size.  The spacing between the pins on the chip should be 0.1 inch.  The output will be the contact on the far right.