The EHS-30 Modular Synthesizer

The EHS-30 was designed and built by me between 1990 and 1993. The design is about 50% PAiA (the CEM modules) and 50% my own design. The EHS-30 is housed in two custom built aluminum cabinets each approximately 2' x 1.5' x .5'. The interface is V/oct and V/Hz on VCO 1-3, and V/oct on VCO 4-6. All control voltage ranges are -5V to +5V. All gates, in and out, are switch triggers (to work with my Korg system).

Specifications:

The schematics for the EKX modules are compliments of PAiA

# of modules

Module

Description

Controls/connections

Schematics

6

VCO

PAiA EKX-40 (CEM3340)

Coarse freq, fine freq, CV1-3, PW/PWM, CV-bus A-C, H/S sync, tri/saw/pulse out

Schematic

2

VCF

PAiA EKX-20 (CEM3320) 24dB/oct

2 inputs, Cutoff, Reso, CV1-3, Reso CV, LP/BP switch, CV-bus A-C

Schematic 1 Schematic 2

2

VCF

Burr-Brown UAF42 + OTA, Multimode 12 dB/oct

Cutoff, reso, CV, LP/BP/HP outputs

Schematic

4

VCA

PAiA EKX-30 (CEM3330)

CV, Initial gain

Schematic

2

VC ADSR

PAiA EKX-10 (CEM3310)

A, D, S, R, 4 CV, pos and neg out, man trigger

Schematic

2

AD/R

 

Attack, release, AR or AD switch, man trigger

Schematic

2

VC Mod generator

PAiA EKX-40 (CEM3340)

Freq, CV, tri/square/pos saw/neg saw outputs, LF or audio switch

Schematic

2

Mod generator

 

Freq, Duty cycle, tri/pulse outputs, LF or audio switch

Schematic

2

Smooth Function Generator

AR envelope, Slew limiter or LFO function

Rise time, fall time, function select

Schematic

1

Envelope Follower

 

Input level, threshold, env out, trig out

Schematic

2

Analog switch

DG201, 1 to 2 or 2 to 1

A, B, common

Schematic

1

VC Phaser

Roland Phase II

Depth, rate, resonance, manual, CV

Schematic

1

VC Wave Multiplier

Josty kit fuzzbox (!) + OTA

Gain, CV, balance

Schematic

1>

Ring mod

ICL8013

A, B, out

Schematic

1

Noise generator

Reverse biased zener diode

Red, white and pink output

Schematic

1

S/H

Incl. LFO

Gate or trig input, LFO rate, clock out

Schematic

2

Diff Amp

 

+in, -in, gain, out

Schematic

1

3-input adder/mixer

 

3 x gain

Schematic

2

6-input mixer

 

6 x gain

Schematic

1

Joystick

 

Y in, X and Y out, 2 trig buttons

Schematic

10

3-jack multiples

 

 

 

Samples:

You can hear some of EHS-30īs sounds here. Everything is done in real time with no overdubbing. Only some reverb and echo is added:

Simultanious FX

EHS-30 meets ARP sequencer

 

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