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The Post-Moog Digitally Controlled Analog Synthesizer
Group Members
•Robert Estelle
•Toan Ho
•Greg Hartl
•Logan Snow
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What:
 Digitally Controlled Analog Synthesizer
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Why:
 Flexibility of digital control
 Recreate classic analog sounds
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Who:
 Hobbyist musicians
 Synth enthusiasts
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Cost:
 Low-cost digital and analog components
 Totaling less than $200
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Synthesize traditional analog sounds
Use modular analog components
Support MIDI input
Store and recall presets
Maintain a low cost
MIDI Microcontroller
VCO
Noise
VCF
VCA1
VCA2
Output
MIDI Microcontroller
VCO
• 1V/Octave control input
•At least 3 Octave range
•Several Outputs:
Noise
•Sine wave
•Sawtooth wave
•Rectangular wave
with PWM
•Triangular wave
•Outputs are mixed before
entering VCF
VCF
VCA2
I’m a big picture ofVCA1
the VCO
Output
MIDI Microcontroller
•White noise
•Adjusted through VCA2
before mixing with VCO
VCO
signals
VCF
VCA1
I’m a big picture of the noise source
Noise
VCA2
Output
MIDI Microcontroller
•Voltage-controlled
resonance and
center frequency
•Multiple Filter Outputs
•High Pass
•Low Pass
VCO
•Band Pass
Noise
VCF
VCA2
VCA1
Output
I’m a big picture of the VCF
•Logarithmic control voltage
•Single
board with two amplifiers
MIDI
Microcontroller
•VCA1 is dedicated to filter output
•VCA2 is dedicated to noise source
•VCA1 output connects to final synthesizer
output
VCO
VCF
Noise
VCA2
I’m a big picture of the VCA
VCA1
Output
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Intuitive interface
Analog feel
Digital control
 Interface must be readable by microcontroller
 Interface must be writable by microcontroller
(in order to support preset recall)
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Digital rotary encoder read by the
microcontroller
LEDs indicate position of knob to user
Display can be reset by microcontroller to
indicate new position
•Noise
•Sine
•Saw
•Tri
•Rect
Attack
Decay
Pulse Width
Sustain
Release
Vibrato
Resonance
Center
Mode
Modulation
Variance
Options
Filter
Filter
LPF
HPF
Fixed
BPF
Tri
Sine
P1
P2
P3
Save
P4
Volume
…
LED Driver
MIDI
Keyboard
LED Driver
…
Microcontroller
I2C DAC
VCO
Control
…
I2C DAC
Filter
Resonance
…
Other Control
Voltages
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Demonstration Requirements
 Will support adjustment of audio parameters
 Will support saving and loading of presets
 Will support MIDI input and produce audio output
Basically – we will play some groovy music for
the class!
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Analog Component Level Testing
 LabView to generate analog test signals
 Oscilloscopes to verify waveform properties
 Circuit tuning and analysis by ear
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Digital System Testing
 Logic analyzer for synchronizing digital signals
 Serial connection for debug output
 Internal status LEDs
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Analog boards are built but untested
Control board layout not complete
Part inventory is incomplete
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(24 Oct.) Complete control board layout
(27 Oct.) Test each analog component board
(31 Oct.) Acquire control board components
(Nov.) Construct control interface board
(Nov.) Program microcontrollers
(1 Dec.) Design and construct enclosure
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Nearly all parts have been received
Voltage controlled boards have been
constructed (VCO, VCF, VCA, and noise
source)
User interface board has been laid out
Working on laying out digital control board
and developing microcontroller software