Shoebox fractalSynth

This is how fractalSynth looks like:

And this is how it sounds (a little tape delay added)

I had once stumbled upon Catweazle's fractal synth. In the circuit benders forum it seemed that the project had come to a halt. But recently I realized that it was going on elsewhere.! Here.
Also, the files can be found in the forum or in
There are two schematics and lots of mp3 samples if you want to hear how it sounds.

I decided against building a PCB in eagle and then etching, soldering, etc. and went for the perfboard. It is a very simple schematic and I pulled through it with relative ease. Just remember to leave a little space around the MicroChip so as to put the simple filter and the voltage stabilizer (a simple 7805 with two capacitors, nothing special).

The schematic mentioned 10K pots but since they are used as simple voltage dividers you can go (as I did) up to 100k with no apparent malfunction. I used a lot of female pin headers on the board (as you can see) and connected the pots and buttons with male pin headers. This is rather flimsy as a connection. You might not be able to go live with such a thing but, it is quick and easy.

The underside of the perfboard is all connected with solder. A difficult to correct method but again, it is quick and I can't wait :)

I used a cardboard box because it was the only thing I could find around me at the time. I had some aluminum panels lying around but I would make noise and the kids would wake up. I have mentioned again the problem I have, making panels for my stuff.

Now I have a noisemaker in a shoeBox :)

I added a simple voltage stabiliser with a 7805 and two electrolytic capacitors and fed the voltage to the chip.

The pots were mounted on the cardboard (a tedious and dangerous job because the cardboard was thin and there is always the risk of ripping it appart.) and soldered with wire and pin headers.

Some special attention was given to the 7-segment LED that connects to the chip. I used 150 Ohm resistors instead of 200 Ohm mentioned in the schematic. The difference is not a big issue. (It would be if 10 Ohms where used for example). The resistors where directly soldered on the led pins because I wanted no other things than the led on the top side of its board in case I wanted to glue it on the cardboard.

So it looked like this:

The whole thing was put in the box after determining which pin of the led went to which pin on the chip. This made the wiring a bit of a rat's nest.

So the final "product" was firmly closed to hide the ugliness of it's interior.

The first tests were a reality.. And it WORKED!!!!!

The next step was to figure how it was working.!!

A big thanks should go here to Catweazle (you can find him in forum) for releasing the source code as well as the schematics. I put a programming header on the board so as to try some things myself.

The next thing is to put the shoeBox fractalSynth through my MC 909 and make a tune out of it !!


Anonymous said...

Excellent! My kids have grown up and moved out, but they were used to strange noises coming from the basement. I built a fraktal synth also, you can check it out at:

Aris said...

I know your site!! I almost etched the PCB you had made but I couldn't find such a seven segment display around. That's why made it on a perfboard. Glad to know that there are more wacky fathers around :)