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MonoVoice

A SID based MIDI Synthesizer !

Courtesy/Thanks to: Buchi

Description: From the site:

After my efforts of connecting a Commodore SID chip to the PC parallel port, i had several people asking how to interface that thing to a sequencer or keyboard. So i had to write some kind of MIDI loopback driver for it; but i did not like that idea and built a standalone box instead: the MonoVoice.


My first idea was to make it 3-voice polyphonic beacuse it has 3 independent oscillators, but then i changed to the idea of a monophonic synth with a three-oscillator voice.


The SID chip is connected to an AVR AT90S8515 Microcontroller running at 8 MHz. The clock signal for the SID comes from a separate 1 MHz crystal oscillator. 16 output lines of the AVR are enough to create a complete 6502 state machine: 8 data lines come from one port, and another port carries the control signals: Reset, Read/Write, CS and 5 address lines. (Further explanation is done by studying the WRITE_SID and RESET_SID functions in the source code.


Warning to all people building stuff with the SID chip: the SID´s output is very delicate. I managed to zap 3 SID chips during development by simply inserting the cable from the MonoVoice into my amp´s jack - the extremely short short circuit duting insertion can do that. So use an opamp buffer to save your SID !

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Added 7/31/2010 2:20:43 PM by mulch

I've just blown my second SID chip.... he's right!!! be careful... although I wouldnt know how to save it with an op-amp buffer IC.... muLch :]

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Files
MonoVoice1.jpg
   Picture of the MonoVoice Synth
MonoVoice1.jpg
   Picture of the MonoVoice Synth
Schematic.gif
   Schematics for the MonoVoice SID synth.
ScreenShot.gif
   Screenshot of the program for programming the MonoVoice.
MonoVoice_sourcecode.txt
   The Sourcecode for the MonoVoice synth. To be used with an Atmel processor.
MonoVoice.zip
   The MonoVoice editor program including visual basic code.
Links
www.buchi.de/MonoVoice
   MonoVoice Infopage
Parts used
SID 6581
   Sound Interface Device
1N4148
   High speed Switching Diode
6N138
   LOW INPUT CURRENT HIGH GAIN SPLIT DARLINGTON OPTOCOUPLERS
BC237
   NPN general purpose transistors
7400
   Quad 2-Input NAND Gate
AT90S8515
   8-bit AVR microcontroller with 8K bytes in-system programmable Flash