krüe :: avrsyn


front overhead shot of avrsyn in desktop case


avrsyn is a digital synthesizer designed by Jarek Ziembicki. It uses an Atmel atmega16 and a 16bit discrete r2r DAC. PCBs and kits are available from Elby Designs. I used a stock board but swapped the original atmega16 and 8MHz oscillator for an atmega32 and 16MHz oscillator.

sound samples


I've built my board into a desktop style case made of sheet aluminum with poplar end panels. Here is a diagram/drilling guide for the front panel:

I didn't label the pots and switches because I think of the avrsyn as a "poor man's chameleon". The hardware is very generic: just a microcontroller with digital and analog inputs, and an audio output. It is easy to write code that changes the synth architecture.

Here are some pictures of the completed case:


I've been steadily adding features to the original avrsyn code. It's very much a work in progress, but you can download what I have so far. Remember that this code assumes an atmega32 running at 16MHz. The current version is avrsyn-2007.12.22.asm.



Since there are not enough controls available on the front panel, some functions are controlled via MIDI continuous controller messages.

pot parameter
0 lfo frequency
1 lfo level
2 dco b detune
3 dcf cutoff
4 arpeggiator threshold
5 arpeggiator rate
6 portamento
7 dcf env level
cc parameter
$30 dca env attack
$31 dca env decay
$32 dca env sustain
$33 dca env release
$34 dcf env attack
$35 dcf env decay
$36 dcf env sustain
$37 dcf env release
$38 dco a level
$39 dco b level
$3a dco a waveform
$3b dco b waveform
$3e dcf resonance
$3f fm depth
switch parameter
$00 xor distortion
$03 dco b enable
$04 dca mode (gate/env)
$05 transpose (down/up)
$06 transpose dco a (down/up)
$07 transpose dco b (down/up)
$08 lfo mode (dco/dcf)
$09 lfo wave (tri/squ)
$0a dcf keyboard tracking
$0c dco a noise
$0d modwheel enable
$0e lfo keyboard sync
$0f lfo random enable
$10 dcf type (lp/hp/band/notch)
$12 arpeggiator enable

Jarek Ziembicki created the orignal syn8535.
Paul Maddox had the idea to update the design to an atmega16 and have a run of boards made.
Laurie Biddulph took the project over from Paul and offers pc boards and full kits.