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Revision 7 as of 2013-05-25 18:02:36

location: MidiVamp2

MIDI Vampire-II

About the MIDI Vampire-II

MIDI Vampire-II (Vamp2) is the next logical extension from Vamp1. You have a synth, now you need a drum machine. And just as Vamp1, Vamp2 is also phantom powered from the MIDI data line, so no batteries are needed.

Vamp2 is a 4 voice drum synthesizer, with 8b, 31.25ksps PWM sound generation, and independent outputs for each voice. The output is sent to 2 stereo 1/8" jacks. If only 1 jack is used, 2 sounds will be mixed on each channel. Depending upon which jack you choose, you can get a different stereo mix. Vamp2 gives control over attack, decay, release, wavetable selection, and has FM, bitcrusher, and frequency sweep effects. It also has comb-filtered noise source with swept resonance, and controllable cutoff frequency.

MIDI Implementation

Vamp2 responds to Note On messages for note numbers 32, 33, 34, and 35. These trigger voice 1, 2, 3, and 4, respectively. A currently playing note will be retriggered if a new Note On message is received. You can set the MIDI Channel by cutting traces on the bottom of the PCB. Vamp2 does NOT respond to Note Off, Sys. Ex., or Real Time messages. It does implement running status. All of the voice parameters can be modified via CC messages.

Voice 1 (Note On #32 - cymbals)

CC #

Parameter

Comments

12

attack

13

decay

14

release

15

pitch

16

frequency sweep

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

17

bit crush

0 is off

18

wavetable selection

0 - 63 is hi-hat, 64 - 127 is ride cymbal

19

wavetable boundary

pseudo loop point for wavetable

Voice 2 (Note On #33 - wavetable synth)

CC #

Parameter

Comments

20

attack

21

decay

22

release

23

pitch

24

frequency sweep

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

25

bit crush

0 is off

26

fm depth

0 is off

27

fm frequency

28

wavetable selection

there are 8 tables

Voice 3 (Note On #34 - filtered noise)

CC #

Parameter

Comments

75

attack

76

decay

77

release

78

cut-off frequency

79

resonance start

when decay is 0, this controls resonance

80

resonance stop

when decay is 0, this does nothing

81

resonance decay

0 is off

Voice 4 (Note On #35 - wavetable synth #2)

CC #

Parameter

Comments

82

attack

83

decay

84

release

85

pitch

86

frequency sweep

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

87

bit crush

0 is off

88

fm depth

0 is off

89

fm frequency

90

wavetable selection

there are 8 tables

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