Emu Systems Modular (2003)

Upper Row in 2003

Overview This is the first analog synthesizer I built (after 1974) and was a replica of the original E-mu Systems Modular synthesizer that was manufactured in California by E-mu Systems from 1972 to 1980. Over 125 originals were built, and the last model was given to Scott Wedge when he left E-mu Systems in 1993 – he still has it. The E-mu Systems modules were updated with new circuit ideas during their life time, and Dave Rossum exploited SSM chips in many of the later module revisions from 1976 onward.

Some of the circuits are unique designs, not available from any other manufacturer. For example the Resonant Filter and the Universal Active Filter (an improvement over the ARP 1047 filter in the ARP2500 Modular).

My workshop 2003

Why Build a Clone? The idea of attempting to build a E-mu Systems Modular clone really took hold when I was in a motel in Scotts Valley in February 2002. I had just visited E-mu Systems, and met up with Scott Wedge and fired up his mint Modular. I was very impressed with the build quality and magic sound, and whilst buying one was not an option in terms of availability and cost, building one was a vague possibility.

A few days later I met up with Riley and Ed at E-mu Systems and realised that they might have some schematics, as they were both into Eu Modulars. I didn’t manage to get any details whilst in the USA, but a few months later when back in the UK both Riley and Ed shared some schematics with me over the Internet. In October 2003 I bought a set of additional Modular schematics from Martin Newcombe (remember the UK Synthesizer Museum?).

The Challenge  Cloning a set of 25 year old analog circuits is NOT easy, even if they were designed by a genius like Dave Rossum. The first stage was to get the schematics onto paper and touch them up so they could be read. The next step was to see what kinds of transistors and IC’s were used, and try and locate them. Whilst there are some easy 2N5828′s and 2N4250′s, there are also rare SSM chips and ultra rare dual matched transistors.

Most of the Op Amps are still around, like the trusty 741 used in control paths, whilst the obsolete 556 can be substituted for. It was soon clear that I would need to replicate the circuits exactly and only once a module was working could I move onto substitution with modern parts. That meant a six month trawl of the Internet looking for rare components…and piece by piece I have managed to acquire every rare part in sufficient numbers to build a large modular!

In its new home

Design Confident that I could at least find the necessary electronics, I could now plan the physical format. The original physical design was based on high quality electronics and mechanics, and I set the same objectives albeit with some compromises and changes: The original modules were 6″ high and 3″, 6 or 12″ wide. I am using a height of 4U  and a width of 90 and 135 mm. This provides more space for the panel layout and enables the modules to be rack mounted. The aluminium front panel designs stick closely to the original, but with some tidying up of layout and the omission of the blue painted surround. Black lettering is etched into the 3mm thick panels (the originals were 1/8″). Two cabinets built in MDF and painted blue. Each cabinet can hold up to 10 modules within a 19″ racking system.  The separate sub-module and module concept of the original has been ditched in favor of one circuit board. An Oakley MIDI interface has been added, so the beast can be controlled via a keyboard.

Outcome  The synthesizer was a great re-introduction into designing and building electronics, and it worked well, even if rather non-standard in panel size and jacks! With limited room in my studio in 2013 it meant that it had to move on and I sold it  to a close friend of mine, here it is in his studio in 2017. Since 2003 I have built a number of Emu Modular modules in the original form factor and a small number of these go on sale in our web store from time to time.

AM2140 PCB

AM2140 Resonant Filter This is the 2 pole state variable filter from the Emu Systems Modular. It is built around the SSM2020 VCA chip and provides LP, BP and HP outputs simultaneously and they can be mixed together. The SSM2020 chip is expensive and hard to locate nowadays but the filter is amazing and its worth tracking down a SSM2020 to build the filter.

I have attached a picture of the completed PCB, this was my first commercial PCB design in 2003 and the PCB’s are still available from Synth Cube here.  I plan to re-invent the circuit using a modern SSI2164 chip, with voltage controlled Q.

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