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 sounds  Use modular analog components  Support MIDI input  Store and recall presets  Maintain a low cost

VCOVCFVCA1 VCA2Noise Output MIDI Microcontroller

VCOVCFVCA1 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

VCFVCA1 VCA2Noise Output MIDI Microcontroller I’m a big picture of the noise source White noise Adjusted through VCA2 before mixing with VCO signals Noise

VCOVCFVCA1 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

VCOVCFVCA1 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 interface  Analog feel  Digital 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

P1P2P3P4 Save AttackDecaySustainRelease Pulse Width Resonance Vibrato Mode ModulationVariance CenterVolume Filter Options Filter LPF BPF HPFFixed Sine Tri Noise Sine Saw Rect Tri

 Microcontroller reads inputs:  MIDI from external music device  Rotary encoder positions through a MUX  Microcontroller controls outputs:  LED position displays using an I 2 C LED driver  Analog control voltages using I 2 C DACs  Mixing levels using I 2 C potentiometers  All digital control is on a single I 2 C bus!

MIDI Keyboard Microcontroller LED Driver 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 untested  Control board layout not complete  Part 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 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