PM-DCASThe Post-Moog Digitally Controlled Analog Synthesizer

Group Members

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

Project Summary

Technical Objectives Create a modular audio synthesis system Support MIDI input Create an innovative user interface Support storage and recall of presets Maintain a low material cost

Motivation Target hobbyist musicians and synth

enthusiasts Recreate classic analog sounds

Financial BreakdownProduct Cycle

CostsQuantit

y Unit Price Price

VCO 1 $18.00 $18.00

VCA 3 $15.00 $45.00

VCF 1 $17.00 $17.00

Noise Source 1 $15.00 $15.00

Digital Control Board 2 $30.00 $60.00

System Interface Board 3 $20.00 $60.00

Interface Knobs 12 $6.00 $72.00

Shipping 3 $30.00 $90.00

Greg's Hours 136 $25.00$3,400.0

0

Logan's Hours 136 $25.00$3,400.0

0

Robert's Hours 136 $36.00$4,896.0

0

Toan's Hours 136 $25.00$3,400.0

0

System Design

Digital Control Board

System Interface

Board

Analog Synthesis Hardware

User Interface

MIDI Keyboard

Debug Monitor

Output Amplifier

User Interface

P1 P2 P3 P4

Save

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

Level

Duration

Attack, Decay, Sustain, Release(ADSR Control)

RKA – Rotary Knob Assembly

Each digital rotary encoder is read by a dedicated microcontroller (PIC16F87)

LEDs indicate position of knob to user Display can be reset by master

microcontroller to indicate new position

PICTURE HERE

DCB - Digital Control Board

PICTURE HERE

MIDI Input

Master Microcontroller(PIC24FJ64GA002)

Debug Port

Rotary Knob Connectors

SIB Connector

DACs

Master Microcontroller

Microcontroller reads inputs: MIDI from external music device Rotary knob positions through I2C Debug commands from serial port

Microcontroller sets outputs: LED positions using I2C LED drivers Analog control voltages using I2C DACs

All digital control occurs on two I2C busses

Digital Control Scheme

MIDI Keyboard

MasterMicrocontroll

er

Slave Microcontrolle

r

I2C DAC

…

I2C DAC

…

VCO Control

Filter Resonance

Other Control Voltages

…

LED Driver

…

Debug Monitor

LED Driver

VCA6

VCA1..4

VCA5

SIB – System Interface Board

VCO

VCF

Noise

Output

+I’m a big picture of the SIB

• Receives control signals from the DCB

• Connects to the power supply• Routes all signals between the

analog boards• Mixes the intermediate signals

Analog Signal Flow

VCO

VCF

VCA1..4

VCA5Noise

Output

VCA6

+

VCO – Voltage Controlled Oscillator

VCO

VCF

VCA1..4

VCA5Noise

Output

VCA6

+VCO

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

• Sine wave• Sawtooth wave• Rectangular wave with

PWM• Triangular wave

• Each output has corresponding VCA

I’m a big picture of the VCO

Noise Source

VCO

VCF

VCA1..4

VCA5Noise

Output

VCA6

+Noise I’m a big picture of the noise

source

• White noise• Adjusted through a VCA

before mixing with other signals

VCA – Voltage Controlled Amplifier

VCO

VCF

Noise

Output

+VCA1..4

VCA5

VCA6

I’m a big picture of the VCA

• Logarithmic amplitude control voltage• Three boards with two amplifiers each• VCA1..4 modulate VCO outputs• VCA5 is dedicated to the noise source• VCA6 output connects to final

synthesizer output

VCF – Voltage Controlled Filter

VCO

VCF

VCA1..4

VCA5Noise

Output

VCA6

+• Voltage-controlled

resonance and center frequency

• Multiple Filter Outputs• High Pass• Low Pass• Band Pass

I’m a big picture of the VCF

VCF

Analog Signal Flow

VCO

VCF

VCA1..4

VCA5Noise

Output

VCA6

+

Task Status

Component Completed

Tested

Voltage Controlled Oscillator

Voltage Controlled Amplifier (x6)

Voltage Controlled Filter

Noise Source

System Interface Board

Digital Control Board

Master Microcontroller Software

Rotary Knob Assembly (x12)

Slave Microcontroller Software

Chassis/Panel

Issues Encountered

Shipping problems Solder flux disaster Old SIB revision sent for fabrication Post-fabrication board modifications Pin size mismatches on DCB

Planned Demonstration

MIDI input from a music keyboard Auditory verification of audio parameter

manipulation Visual verification of user interface correlation

with audio parameter adjustment Saving and loading of presets

Questions?

?