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Revision 12 as of 2013-05-25 17:41:47

location: MidiVamp1

MIDI Vampire-I

About the MIDI Vampire-I

MIDI Vampire-I (Vamp1) is just about the smallest digital synth we could make (i'd hate to think how big the smallest analog would be!). It boils down a MIDI synth to its basics - MIDI in, processing, audio out. And, in doing so, it reduces the power consumption to the point that it can be phantomly (or vampirically) powered from the MIDI data line itself! Just plug in and play, no batteries or powersupplies.

Vamp1 is a 4 voice, polyphonic wavetable synthesizer, with a mono, PWM output at 14b, 31.25ksps. It gives control over attack, decay, wavetable selection, and has FM, AM, reverb, and bitcrusher effects. It also has a variable pulse width, square wave synth, which is not wavetable based, and can generate filter sweep type sounds.

MIDI Implementation

Vamp1 responds to Note On and Note Off messages. If 4 notes are being held, then no new notes can be played. But, if less than 4 notes are being held, then new notes can steal currently decaying notes. You can set the MIDI Channel by cutting traces on the bottom of the PCB. Vamp1 does NOT respond to Sys. Ex. or Real Time messages. It does implement running status. All of the voice parameters can be modified via CC messages.

MIDI CC Messages

CC #

Parameter

Comments

10

wavetable selection

there are 16 tables, table 1 is PWM

11

attack

12

decay

13

frequency sweep

64 is off, 0 - 63 is down, 65 - 127 is up

14

fm depth

0 is off

15

fm frequency

16

bit crush

0 is off, 127 is 1 bit

17

reverb depth

0 is off

18

PWM "cut-off"

19

PWM "cut-off" decay

64 is off, 0 - 63 is down, 65 - 127 is up

20

am frequency

0 is off

Firmware

If you want to modify your Vamp, there are plenty of fun things to do. You can put in your own wavetables, or modify the frequency ranges pretty easily. These are just done with lookup tables that can be swapped out. The code itself is written in AVR assembly, which we apologize for, but it was the only way to get so much into such a small space. We have some Pure Data wavetable creators that you can use to take .wav files and convert them into assembly lookup tables. You can also generate sounds within Pure Data and make wavetables from those as well.

Documentation

Files: Version 1.0