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AVR Synth


MyCo

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I've been working on my version of an AVR Synth. Now it looks like this:

synth1.jpg

synth2.jpg

The only addition to get it running is a power supply, I've built my own:

supply.jpg

Total investment: 16 Euro and ~100 hours til now

The AVR is an Atmega644 running at 20MHz (the crystal and its caps are under the chip), so now I've 64kB of Flash memory and I use 16kB of it for a wavetable. At the moment it sounds like nothing. I'll come back when I've got something to listen to it  ;)

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Very cool!! I've been thinking of building one of these but don't want to spend the $ for the kit from Elby Designs. Are you planning on posting schematics, code etc? If so I'd really be pleased. Elby doesn't provide the schematics to my knowledge. What are you using to program the processor?

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Yes, I make it open source. But at the moment I don't have a schematic, because it is so simple, that I draw the connections directly in a PCB-Layout programm before I built it  :)

To program the AVR, I use an In-System-Programmer (Flat cable on the left) with PonyProg, and AVR Studio 4 to write/compile the Assembler. All of this parts are Open Source / Freeware, too.

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So, here is the first preview. I've finished my first attempt to build in a filter...

http://yedey.com/other/filtertest.mp3

It demonstrates the filter (cutoff & resonance) and wave morphing from saw to square. It already has 7 different waveforms and it can morph between all major waveforms (sine, saw,square triangle). The filter introduces a lot of noise, which I tried to kill in the DAW.

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ok, here is the version without postprocessing (except normalization):

http://yedey.com/other/filtertest_org.mp3

20% of the noise in there is from my PC (I use the soundcard from the mainboard, which is noisy)

the other 80% are from the synth.

I found out, that most of the synth noise comes from the midi input, that means, as soon as I send a midi message, I can hear a noise. The clip above uses 3 automations, so there are a lot of midi messages which generate a lot of the noise. I think I've to put some more capacitors on the board to filter the voltage drops of midi in optocoupler...

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