DIY DSP

for musical applications

This site aims to inform friends about an "open source" Do It Yourself project.  Its a wonderful and rewarding opportunity to explore the musical application of Digital Signal Processing.  Its purpose is to collect resources in a central location, explain how to get started, and provide a means to showcase our work in this field.  

You may have thought that the investment required to begin experimenting with DSP technology would be prohibitive to all but the most wealthy of companies, but with this system, you can get started coding your own algorithms, on a real DSP, for under $100.  

The DSP board itself is fully self contained, with power supply, stereo audio inputs and outputs, and a removable memory chip.  Its available for about $89.00 from many electronics distributors, and is made by Analog Devices, Inc.  The resources below will show you how to take this commercially available DSP evaluation board and add flash memory, midi in/out, battery power, and your own custom synthesis and effects algorithms, effectively turning the DSP into a portable, midi controlled, custom synthesizer or effect, at a price any musician can afford.  

Ever heard of a synthesizer by called the "Nord Modular"?  Its a DSP in a box with some keys and knobs.  It costs about $2000.  Code for it is generated by a host computer and downloaded to the machine's memory.  The Nord then runs this DSP code, synthesizing or manipulating sound, while under midi control.

This project is just like that, but in this case, instead of connecting preprogrammed "modules", you can create your own algorithms from the ground up.  The DSP can then be reprogrammed with your own code. This means you can program this device to manipulate sound any way you can imagine. You can program that effect you've always wanted, or create a completely unique synthesis engine, with sounds never before heard.  

I made this page to get more people interested in this project and expand its user base.  I'm hoping to help people curious about programming sound apps get started, and let musicians know about the potential of this system.  The more people developing for this machine, the more effects and synthesizers will be available for the community.  Its not easy, but much of the work has already been done for you.  If you want to help, or want to know more about this completely custom synthesizer, mail me at christian@dslab.com.

ALIENOPERA.MP3:
alienopera.mp3
Tony asked me for an example of some of the synths on this page. This is something I did some time ago. It contains SNYTH on the 'melody' (if you can call it that, its more of a drone), KS on the 'percussion' (the clicks, noise hits, and plucked string sounds) and a shortwave radio through REDUX for the other wierd noises. Its all run through an alesis wedge for delay and reverb effects.

My first DSP effect "REDUX":
Source code: redux.dsp
2181 executable: redux.exe
Its a bit quantising and sample rate decimation effect.

My first DSP synthesizer "SNYTH":
Source code: synth.dsp
2181 executable: snyth.exe
A new form of delay line synthesizer somewhat akin to bowed string physical modeling... maybe.

My second DSP effect "SVF2":
Source code: filter2.dsp
2181 executable: filter2.exe
A state-variable filter w/ selectable output band and Q controls... a modification of Shifty's SVF code.

My second synth "KS":
Source code: ks.dsp
2181 executable: ks.exe
A Karplus-Strong plucked string synthesis engine by Ethan Bordeaux modified for midi control by me.

"DELAYS":
Source code: delays.dsp
2181 executable: delays.exe
A second Karplus-Strong plucked string synthesis engine by Ethan Bordeaux modified for midi control by me. This one has an 8-tap filter instead of the simple averaging filter in the feedback loop of the delay line. Each tap's values are controlled by a midi controller... pretty wild.

"BEEP":
Source code: beep.dsp
2181 executable: beep.exe
I came across a neat little oscillator type by accident a while ago... I've incorporated it into a synthesizer with some new looping envelope code I wrote which allows FM of the filter from sub-audio to audio rates, and AD envelopes. This and the strange oscillator make for a pretty cool new synthesizer I call 'BEEP'.

in the pipeline currently...

• Ok... this is wierd. I came up with this idea for a wavetable type synth where the wavetables arent static, but calculated on each new cycle of the waveform by some simulation of a physical system. My first idea was an IKA based system where complex interdependent pendulums are set in motion on each new note, and as the note decays, the pendulum dies down. Imagine if you will, a pendulum. This simple system can be described mathematically in a computer. Now imagine that pendulum system turned on its side, so that its top is at the left and swinging bottom at the right. This simple system forms the waveshape for the wavetable. With only 1 pendulum, the output is a simple amplitude modulated sawtooth wave... but several interconnected pendulums, a complex 'mobile' of sorts, this waveshape would be: 1. complex 2. variable over time 3. easy to calculate 4. sound pretty cool. I had some other ideas for simple physical systems that would give similar results... The most intriging of which I named "SPROING", a system in which rotational springs were added to the pendulums as a way to put different forces on each segment, in addition to gravity, arm length, and mass. Here's the wierd part. I was researching how I was going to do this... model these physical systems... and I put some stuff in Google and I came across this page: Scanned Synthesis It turns out that Verplank, Shaw, Mathews, Cook, and Smaragdis have already implemented something very similar in CSound circa 1998. They called in Scanned Synthesis... it works basically the same as my concepts, but they definately explain it better. Anyway, I've set out to recreate this in my 2181... IN REALTIME... I'm almost there... I'll keep you posted... :)

To learn more, follow these links: