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Emu Modular [Retrozone]

Modular Synthesizer By Simon Lowther
Published July 2000

Emu Modular Synthesizers (Retro)

Emu Systems have been synonymous for so long with samplers and sampling that it may surprise some to learn that they started out making analogue synthesizers — and that through the '70s and early '80s, they produced some of the biggest, most sophisticated modular synths ever made. Simon Lowther gets out his patch cords...

Dave Rossum started Emu Systems in 1971 as a true garage operation in the best American tradition. His first product was called the Emu 25, of which he claimed to have sold a grand total of two! History is unclear on exactly what the Emu 25 was, but it seems to have been a sort of cross between a Minimoog and ARP 2600 with some patch sockets on the back panel. Quickly tiring of prepatched machines, Rossum decided that a modular instrument would be much more interesting to design. He also reasoned, probably quite astutely, that there was a market for this type of synth not just amongst hobbyists but, more lucratively, amongst universities.

Joined by college friend Scott Wedge, Rossum set about building a synthesizer that would be top‑notch in every way. The company literature of the time suggested that they felt more like craftsmen than manufacturers, aiming for the state of the art using the highest‑quality components. If Emu had an advantage over the established players it lay in their knowledge and awareness of the latest technologies, including the emerging possibilities of computer control, and their willingness to incorporate those ideas into a musical instrument. They made no secret of the fact that that they looked at what the competition had to offer before setting about designing their modules — but their naiveté showed when they took the sometimes over‑optimistic spec sheets of competitors at face value and worked hard to improve on them!

Climbing The Walls

Emu Modular Synthesizers (Retro)

The wood cabinets that house the Emu modular are very classy (read expensive, and worryingly South American rain forest in appearance), and the knobs and aluminium front panel are unusually solid. I wasn't sure about the brushed‑aluminium look when I first saw an Emu in the '70s, when everything in the synthesizer world was supposed to be black and moody, but today an Emu modular actually looks rather modern and trendy — almost like a Doepfer's big brother.

The individual modules themselves are six inches high and multiples of three inches wide, so systems grow at an alarming rate — any Emu modular worth its salt will be very large indeed! The panel layout also rather lacks the cohesive approach that Robert Moog put in to his designs. Emu suggested starter systems but offered no standard models like Moog's IIIC or 55. Instead, the Emu modular was based around a series of '1000‑series' submodules (potted plastic‑encapsulated modules), which are used to form the '2000 series' of modules (the front panels), which then form the '4000‑series' systems (the synthesizer itself). However, Emu seemed to spread modules around without following any logical layout; the arrangement of modules makes no effort to reflect the conventional signal flow of VCO, VCF, VCA flowing from left to right as many analogue synths do.

Bird Song

The dual envelope generator module, with initial delay time control to delay the onset of the envelope.The dual envelope generator module, with initial delay time control to delay the onset of the envelope.

Most older analogue synths have a characteristic sound, and Emu's are no exception. They put out a very solid, precise, clear and full sound, right across the frequency spectrum from a thundering, rather than pounding bass to whistling highs. Emu aimed to achieve a wide dynamic range with low distortion, and the resulting sound has the bright bite of an ARP, but with a lot more power and weight reminiscent of a Moog or early Oberheim. A quick comparison showed that in terms of power and fullness of sound, one Emu VCO can make multi‑VCO offerings from quite a few other analogue manufacturers sound rather unimpressive!

The actual synth pictured opposite, which I played at the EMIS Synth museum in Bristol while writing this retro, is intriguing. The unknown original owner who specified the modules seems to have had some interesting ideas about digital control and patching which suggest he required live control and sequencing functions. The EMIS synth is quite modest in size for an Emu modular, comprising three VCOs, a noise generator, sample and hold, a low‑pass VCF and resonant multimode VCF, a single VCA (which many would find limiting), dual ADSR, VC clock and sequencer. There are also some multiple panels, a quad quantiser, dual LFO, ring modulator, quad inverter, and a sequencer disguised as a programmer and memory address module. The number of modules is not huge — in synthesis terms it is similar in scope to an ARP 2600 — but what it does and how it goes about it is very different.

The Main Modules

Unlike most synth designs, Emu laid out their circuit boards parallel to the modules' front panels.Unlike most synth designs, Emu laid out their circuit boards parallel to the modules' front panels.

The VCO has individual jack outputs for sine, sawtooth, triangle, and variable‑pulse waveforms, and there is an onboard mixer to mix them to a single jack output if desired. Of course, you also get PWM and sync. Emu's modules often incorporated novel design features, and the VCO provides both exponential and linear inputs for frequency control, which is fairly unusual (traditionally, linear inputs are used when control voltages are passed though for a smooth response, while exponential are preferred for audio applications). Most synths have an exponential input, which allows you to use an LFO for normal vibrato duties. If you speed the modulation up into the audio frequency, however, things become a harmonic mess as lots of unpredictable frequencies are generated. Linear control gets around this and is good for getting tuneful FM sounds, because the harmonics and sidebands generated are in tune — and remember we are talking about an instrument from the early '70s, way before the DX7! The actual pitch stability of the VCO is pretty good: although it's obviously an analogue design, it doesn't take too long for the pitch to settle down, and it doesn't wander all over the place. Emu also thoughtfully provided their VCOs with selectable keyboard control switches for those customers with two keyboard controllers.

Another notable module is the noise source. It has a knob to sweep the output from white through to pink, using a 6dB filter, and onto lower frequencies for those burbling random modulation sounds (a bit like smoothed sample and hold). This module produces a very musical, smooth white noise. You might be forgiven for thinking that all noise generators are the same, but hearing this is a bit like first hearing an expensive digital reverb: from then on others just don't cut it.

Following the signal chain, we come to the VCF — always one of the most interesting modules for rabid synth fanatics! Emu gave their VCF coarse control for sweeping the cutoff frequency, and also a fine frequency control for critical adjustments. This filter does have its own sound, as it's based on Emu's own design. It has a glorious and dangerously vicious resonance sweep and smoothly goes into self‑oscillation, but also has the ability to wreck lesser speakers once oscillating. If you listen carefully you can hear it picking out harmonics very precisely when swept, which is very pleasing.

The synth I used also has a resonant multimode filter, with mixable band‑, low‑, and high‑pass outputs. This provides cutoff frequency and resonance knobs, but no modulation inputs, so the output is static unless you turn the cutoff frequency knob in rea l time. It seems overly simple, but I like to use it to create a sort of formant to feed back into the VCF for more complex filtering. Emu, in fact, suggested using multiple units for this purpose, and also made a multimode 12dB filter offering high‑, low‑, band‑pass and notch modes simultaneously.

The VCA offers both linear and exponential modes, which is nice, as each setting takes on a different character. You get plenty of control inputs, plus an initial gain control knob if you want to leave the VCA open for those cosmic drone moments.

The Supporting Cast

The controls for the digital sequencer on the innovative 4060 digitally scanned keyboard.The controls for the digital sequencer on the innovative 4060 digitally scanned keyboard.

Most of the other conventional synth modules are as you would expect. The envelopes are DADSR designs — basically a standard ADSR with an additional variable delay for delaying the start of the envelope cycle. An additional module allows voltage control of the times and levels too. The LFOs are quite basic, with square and triangle outputs: each has a gain output, but disappointingly no CV inputs. Of course, if you want more complex modulations you can use a VCO in low‑frequency mode. There is a ring modulator, which is of high quality and sounds smooth.

I was surprised to find that there were no general‑purpose mixers on the synth I used. This is not a disaster, as most outputs have attenuators, and quite a few inputs have them too. But quite how you are supposed to mix VCOs... Emu did make a few different mixers, however, from sophisticated voltage‑controlled modules down to a 3‑into‑1 unit found in their 'Pot Pourri' multi‑purpose support module, which comprised an LFO, voltage source, mixer disguised as a summing amp, inverter and comparator (a type of voltage switch).

The full range of modules eventually made available covered most eventualities (see the 'Complete Works' box on page 268 for a full list). The panel is clearly laid out, and as long as you can actually reach the knob you want, it is straightforward to use. Today, a sampler would be a useful accessory for those moments when you need repeatability, as there are enough controls to make recreating a sound a good test of anyone's memory!

Catalogue Of Innovations

A couple of Emu's more unusual modules, the Hex Inverter and Triple Or Gate.A couple of Emu's more unusual modules, the Hex Inverter and Triple Or Gate.

Emu were notable for being one of the first synthesizer companies to explore digital control. They made analogue sequencers, but went way beyond this, producing various logic and micr oprocessor‑based modules for controlling monophonic sequences. These included a memory address generator, a memory module that records a voltage and digital codes to 6‑bit accuracy, and a programmer. You could combine these to store and play back very long strings of voltages, and a tape interface was available to store your creations. From within a sequence you can program rests, add emphasis, modify tempo, or switch sequences. You can even fire the output back into itself, to 'auto‑create' different sequences. The display runs from 000 to 377, which I find perplexing! Using the sequencer is no picnic, however, and requires a full mastery of '70s‑style computer jargon with its talk of noughts, ones, resets and lamps.

The sequencer also has a socket for voltage control of clock speed, which shows that Emu were not just thinking about 8‑note repeating riffs. I suspect the intention was that it could be used for timbre control, or maybe they did not even have specific applications in mind when developing these devices: the availability of digital memory just meant new areas could be explored. After all, it was a time when synthesis was about experimentation.

My favourite of the more unusual Emu modules is the voltage‑controlled clock. This features a built‑in LFO with mixable pulse and saw waves, of which you can control the frequency and pulse width. By messing around with the waveform levels you can gate the clocks to one of two outputs, resulting in complex alternating syncopated triggers from two outputs. This is great for polyrhymic pulsing rhythms.

There was also a series of logic modules, for use with the sequencer modules. These included a hex inverter, which was six simple inverters, and functioned more like a switch depending on what sort of pulse it received, and a 'Triple Or Gate' which logically outputs when it sees a 'logical input' (no, I don't understand it either...). A triple latch module and a pulse shaper, which is useful for converting audio to digital triggers, complete the line‑up.

With some of these modules, you suspect that the designers must have been doing things just because technology meant they could! The hex digital inverter, for example, came into being simply because a CMOS hex inverter chip became available which gave just those functions. Today, much of this digital control is really a matter of curiosity, and does not give instant unusual results. You can often obtain better results by just plugging in a MIDI interface and playing the synth!


If you look inside an Emu modular you will see some clever engineering, such as its double‑sided circuit boards, which were pretty advanced for the time. Once inside, you realise how unlikely it is that you are ever going to rearrange the modules into a more ergonomic layout for your own way of working, simply because of the way the synth is constructed. You'll also understand the reason why the modules' front panels are so big — not only to spread the knobs out on the front, but also because the circuit boards inside are laid flat against the front panel and not away from it at right angles, as on a Moog. While inside, you may also notice that some of the modules are potted in resin. This was sometimes done to protect design secrets, and perhaps to make the synth more stable during temperature changes. If this was the reason, then it seems to have worked: the Emu modular I tried is a stable synth even today. There is some crosstalk, but it is a credit to the engineering that it still works well.

Curiosity is not the only reason why you might want to open up the cabinets. Modular synth users have always complained when patch leads eventually obscure everything, and Emu responded by allowing users to create favourite custom routings internally, wired using small jumper cables. You could internally connect modules and custom modulation to hard‑wire your most frequently used routings. It's not something you will change very often, though, as you must take the back panel off with a screwdriver. The ability to do this was a big selling point, which Emu called "patch over firmwire", though the layout doesn't lend itself to guessing what is wired to what! Later Emu developed this further, with prepatch modules that allowed you to switch between a few internally selected routings at the turn of a knob. This was very useful for live performance.

After all this helpfulness it might come as a bit of a shock to find the following statement in the manual: "We have deliberately avoided calibration marks on the panels, with the intent that the user could add them as he wishes..."


Emu's keyboards were also innovative: they lacked expression controllers, with no wheels or ribbons, but they did offer the original digital scanning keyboard around 1973. The range evolved to include a monophonic unit and a 5‑octave polyphonic unit, featuring split and voice‑allocation modes. Emu later improved on this design and added a built‑in 2000‑note digital sequencer operated from a keypad with a breakout box for the numerous connectors. Called the 4060, the sequencer was expandable to a 6000‑note capacity (astonishing for the time) and featured portamento, transpose, hold and unison for each half of the split point. It was externally clockable and even included a tape interface for storing sequence data. You could create a number of sequences for playing back simultaneously, but editing seemed limited to tempo and erase. For its time it was amazing. Emu had a nice sideline licensing out some of this keyboard technology, firstly to Oberheim for use in their SEM‑based synths and later to Sequential for the Prophet 5.

See You Later, Emulator

Although Emu were still a small company in the mid‑'70s, they had carved out a niche for a high‑end specialist product and were very well respected amongst those in the know. They invented and licensed out their keyboard technology and had a hand in developing SSM music chips, but they really only had one product, which from a business viewpoint must have made their longer‑term viability and survival very doubtful.

A quick chat with Derk Hagedorn at Emu confirms the reason why they moved away from the modular. It wasn't that Emu discontinued it but, like much analogue technology, it simply fell out of demand in the late '70s and early '80s. Orders just dried up as pop musicians discovered more affordable programmable synths and academics moved into new digital sound manipulation techniques. Emu needed a new product badly: seeing an opportunity, they moved into sampling with the Emulator I and the future was set.

The Emu Modular systems shown in this article are housed at the EMIS synth museum in Bristol (0117 956 1855). Thanks to Andy Horrell for photos and assistance.

Where Are They Now?

Emu never had a particularly high profile compared to Moog or ARP, but they did have a dedicated following. Frank Zappa had a large system, which apparently he had set up as a five‑part brass section for most of the time. Patrick Gleeson did a couple of LPs using mainly Emu modules — I've got Rainbow Rising in my record collection and there is the unmistakable sound of Emu all over it. Amazingly, Gleeson took the whole thing out on the road: I've never seen a picture of his full system but it wasn't small, reportedly containing 96 VCOs. Tangerine Dream had some custom Emu equipment and YMO were confirmed users. Vince Clarke has one tucked away somewhere, as does Hans Zimmer. You can see one at the Turnkey Sample Museum in London, there is one at Emu's synth museum, and quite a few universities have them. About 100 were made in total.

If you want to buy an Emu modular today, remember that they are quite rare, so shopping around is not easy. They vary in size a lot, and you are not, realistically, going to be able to negotiate buying just the bits you want! The one in the EMIS museum could sell for around £5,000, while a larger one easily could be £10,000‑plus. If you want the sound of an Emu modular without spending this sort of cash, you'll find a couple of samples in the Emu Vintage Keys module. There are also some seriously large samples locked away in the vaults of Emu R&D, but they have yet to, and may never, make an appearance on a module.


It would be unfair to mention the Emu modular and ignore the Audity. This was Emu's attempt to build a mega polysynth, based on expertise they had gained from the modular and the development of some large and sophisticated voice cards. In 1978, its planned spec was well ahead of the game, being 16‑voice polyphonic and programmable, with complex modulation and multimode filters. All this power, however, was accompanied by a planned price tag of more than $50,000, and consequently the machine never made it into full‑scale production, although one remains at the Emu headquarters in California (see the Emu feature in SOS October '95).

The Complete Works

The complete list of all the modules and submodules available to those buying an Emu modular was pretty comprehensive...

The complete list of all the modules and submodules available to those buying an Emu modular was pretty comprehensive...
Catalogue Ref. List Price (1970s) Function
1000 VCA $40   VCA
1010 DVCA $55   Dual VCA
1100 VCLPF $75   VCF (low‑pass)
1111 VCHPF $80   VCF (high‑pass)
1122 UAF $120   Universal Active Filter (multimode)
1140 AUAF $60   Audio Universal Active Filter
      lower quality than the 1122)
1201 VCO $80   VCO
1210 WC $55   Wave Converter (converts a sawtooth
      to sine, triangle, inverted saw and pulse)
1340 VCLAG $55   Voltage‑Controlled Lag Generator
1350 VCDTG $75   Voltage‑Controlled Dual Transient
1351 VCTG $65   Voltage‑Controlled Transient Generator
1400 NS $55   Noise Source
1410 S&H $60   Sample and Hold
1420 HGA $50   High‑gain Amplifier
1430 RM $45   Ring Modulator
1440 EF $60   Envelope Follower
1500 VCC $95   Voltage Controlled Clock
1540 MAG $150   Memory Address Generator
1545 MEM256 $240   Memory Module
1546 PROG $185   Programmer
1547 TI $250   Tape Interface
1900 USMB $8   Universal Submodule Mounting Bboard
1905 PSS $220   Power Supply
4003 KYBD $250   Keyboard
module in multiples of three inches. MODULES
NOTE: the number after the price relates to the width of the module in multiples of three inches.
2000 VCA $190 2 VCA
2010 QVCA $375 3 Quad VCA
2100 VCLPF $240 2 VCF (Low‑pass)
2110 VCHPF $240 2 VCF (High‑pass)
2120 UAF $400 3 Universal Active Filter
2140 RF $195 1 Resonant Filter
2145 FC $150 1 Filter Controller (allows
      2140 to be voltage‑controlled)
Catalogue Ref. List Price (1970s) Function
2200 VCO $400 3 VCO
2210 SPVCO $225 1 VCO (Saw/pulse)
2340 VCLAG $200 1 Voltage Controlled
      Lag Generator
2350 DTG $400 3 Dual Transient Generator
2355 VCTGI $125 1 Voltage‑Controlled Transient
      Generator Input Unit (allows 2350 to
      be voltage‑controlled)
2400 NS $145 1 Noise Source
2410 S&H $145 1 Sample and Hold
2420 DP $160 1 Dual Preamp
2430 RM $165 1 Ring Modulator
2440 EF $160 1 Envelope Follower
2450 QI $95 1 Quad Inverter
2451 POTP $220 2 Pot Pourri module (contains summing
      amp, LFO, inverter, comparator, digital
      inverter, ‑10V source, +10V source)
2455 MIX $195 1 Four‑input Mixer
2460 DR $255 1 Dual Reverb
2500 VCC $300 2 Voltage‑Controlled Clock
2510 8AG $375 3 Eight‑position Address Generator
2520 VSOU $495 4 Voltage Source Output Unit (the 2510
      & 2520 together form a sequencer)
2530 AS $210 2 Quad Analogue Switch
2540 MAG $330 1 Memory Address Generator
2545 MEM256 $330 1 Memory (presumably 256 bytes)
2546 PROG $295 1 Programmer
2547 TI $500 1 Tape Interface
2550 HDI $90 1 Hex Digital Inverter
2551 TO $85 1 Triple OR Gate
2552 TL $125 1 Triple Latch
2553 DOS $100 1 Dual One Shot
2800 3" BP $15 1 3‑inch Blank Panel
2801 6" BP $18 2 6‑inch Blank Panel
2802 9" BP $21 3 9‑inch Blank Panel
2905 PS $250 1 Power Supply
2906 MULT $40 1 Multiple Jack
4000 KYBD $780   Mono Keyboard
4050 PLYKBD $1020   Poly Keyboard
4060 KBD/SDEQ $3000   Poly Keyboard/Sequencer