The Post-Moog Digitally Controlled Analog Synthesizer

Group Members

•Robert Estelle•Toan Ho•Greg Hartl•Logan Snow

What: Digitally Controlled Analog Synthesizer

Why: Flexibility of digital control Recreate classic analog sounds

Who: Hobbyist musicians Synth enthusiasts

Cost: Low-cost digital and analog components Totaling less than $200

Synthesize traditional analog soundsUse modular analog componentsSupport MIDI inputStore and recall presetsMaintain a low cost

VCO VCF VCA1

VCA2Noise Output

MIDI Microcontroller

VCO VCF VCA1

VCA2Noise Output

MIDI Microcontroller

I’m a big picture of the VCO

• 1V/Octave control input•At least 3 Octave range•Several Outputs:

•Sine wave•Sawtooth wave•Rectangular wave with PWM•Triangular wave

•Outputs are mixed before entering VCF

VCO

VCO VCF VCA1

VCA2Noise Output

MIDI Microcontroller

I’m a big picture of the noise source

•White noise•Adjusted through VCA2 before mixing with VCO signals

Noise

VCO VCF VCA1

VCA2Noise Output

MIDI Microcontroller

VCF

•Voltage-controlled resonance and center frequency•Multiple Filter Outputs

•High Pass•Low Pass•Band Pass

I’m a big picture of the VCF

VCO VCF VCA1

VCA2Noise Output

MIDI Microcontroller

I’m a big picture of the VCA

•Logarithmic control voltage•Single board with two amplifiers•VCA1 is dedicated to filter output•VCA2 is dedicated to noise source•VCA1 output connects to final synthesizer output

VCA1

Intuitive interfaceAnalog feelDigital control

Interface must be readable by microcontroller

Interface must be writable by microcontroller(in order to support preset recall)

Digital rotary encoder read by the microcontroller

LEDs indicate position of knob to user

Display can be reset by microcontroller to indicate new position

P1

P2

P3

P4

SaveSave

Attack

Decay

Sustain

Release

Pulse Width

Resonance

Vibrato

Mode

Modulation

Variance

Center

Volume

Filter

Options

Filter

LPF

BPF

HPF Fixed

Sine

Tri

•Noise•Sine•Saw

•Rect•Tri

MIDI Keyboard

Microcontroller

LED Driver

I2C DAC

…

I2C DAC

…

VCO Control

Filter Resonance

Other Control Voltages

…

LED Driver

…

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!

Analog Component Level Testing LabView to generate analog test signals Oscilloscopes to verify waveform properties Circuit tuning and analysis by ear

Digital System Testing Logic analyzer for synchronizing digital

signals Serial connection for debug output Internal status LEDs

Analog boards are built but untestedControl board layout not completePart inventory is incomplete

(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

Nearly all parts have been receivedVoltage 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