OGEE Specifications

OGEE is a combination of my own design, and circuits from the Electronotes newsletter. Schematics are provided for circuits that are my own design; for circuits out of Electronotes, the reference is given.

OGEE is built in two cabinets, on four 7" high rack panels.

 Cabinet 1  
ModuleFront PanelFeaturesSchematic
Reference
Power Supplies +/- 15 volts at 1 amp, +5 volts at one amp, in each cabinet.
VCO's 1, 2, 3 Saw, Tri, Pulse outputs. PWM and Linear FM inputs. Hard and soft sync, LFO switch. Based on SSM2033 chip
VCA 1, 2 AC and DC coupled inputs, exponential and linear control, gain control. Based on CES 3330 dual VCA chip. Schematic
ADSR 1, 2, 3 Transient Generator with Attack, Decay, Sustain, Release and Output Level controls. Gate and trigger inputs, manual trigger button. Based on CES 3310 ADSR chip. Schematic
Low Frequency Oscillator LFO with Triangle, Sine, and Pulse Outputs. Schematic
Psuedo Random Noise Source Digital psuedorandom noise source with switchable internal or external clocks, white or pink noise outputs. Digital portion based on Electronotes EN-76 design, analog portion my own design. Schematic
Sample and Hold Based on PMI SMP-10, with internal or external clock. Internal clock is a 566 based VCO. Schematic
4 pole Bandpass VCF Voltage controlled bandpass with voltage controlled Q adjustable into oscillation. Two tracking and one reverse (inverted) C.V. inputs, Q adjust, Initial Frequency controls. Based on CES 3320 VCF chip. Schematic
4 pole Lowpass VCF Voltage controlled 4 pole lowpass with voltage controlled Q adjustable into oscillation. Two tracking and one reverse (inverted) C.V. inputs, Q adjust, Initial Frequency controls. Based on CES 3320 VCF chip. Schematic
Multimode Filter Voltage controlled State Variable filter with bandpass, lowpass, highpass, and notch outputs, Q control. Based on CES 3320 VCF chip. Schematic
Balanced Modulator Four quandrant multiplier built from two summed two quadrant multipliers (OTA's). AC coupled inputs. Schematic
Voltage Controlled Pan Pans input to left and right outputs based on control voltage or Position control. Schematic
Reverb Spring reverb module. Schematic
Mixer Four input mixer with switchable stereo or mono outputs, individual attenuators and left-right gain, two line outputs and headphone output with bass boost. Schematic

 Cabinet 2 
ModuleFront PanelFeaturesSchematic
Reference
Keyboard Interface Keyboard connected by 5 pin DIN connector. This module provides multiple control voltage, gate, and trigger outputs, plus some variable (pot controlled) DC control voltages.
16 event Sequencer 16 event analog sequencer multiplexes 16 10 turn pots. Internal or external clock, Step, Single Run, and Run modes. Original design. Schematics
Envelope Follower 0db and +20db inputs, gain control, envelope, gate, and trigger outputs. Uses cascaded envelope follower design from Electronotes EN-88 and EN-89. Schematic
Multiplexer 4 input, one output MUX. Internal or external clock, rate control, single step button. Original design. Schematic
Voltage Controlled Analog Delay Line Never quite got this one working (notice the holes). Future project.
Waveform Animator From Electronotes EN-87. Sort of a PWM for saw and triangle waveforms. Output looks real interesting on a scope. Notes
Timbre Modulator From Electronotes EN-72. Schematic
Voltage Controlled Transient Generator ADSR with control voltage inputs for Delay, Attack, Decay, Sustain, and Release. Based on CES 3310 chip with added circuitry to provide voltage control. Schematic
VCO4 VCO with saw, pulse, triangle, sine, and suboctave square outputs. The suboctave has a fixed rate Pulse width modulation. Hard and soft sync, linear FM and control voltage inputs, LFO switch. Based on SSM 2033 VCO chip. Schematic
Variable Slope Filter From Electronotes EN-72. Built this without knowing what a variable slope filter would sound like. I wasn't too impressed; it sounds like a 2 pole lowpass.
Switched Capacitor (Commutating) Filter
VCA 3, 4 AC and DC coupled inputs, exponential and linear control, gain control. Based on CES 3340 dual VCA chip. Schematic

You may notice there is no keyboard mentioned. Originally I had built a 5 octave low note priority scanned keyboard with portamento and joystick controlled pitch bend, but it got trashed. Future project: Build a Midi to CV interface (probably will just buy a kit).


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