Analogue Systems RS Integrator

Once upon a time, all synths were like this — discrete analogue sound‑generating and sound‑processing modules, connected in any configuration the synthesist cared to dream up. If you like that idea, Analogue Systems are providing a new alternative to expensive antique systems. Chris Carter does the time warp again...

If the rumours are to be believed — and, according to a record company exec I had a chat with the other day, they are — a Britpop/guitar band backlash is just around the corner and electronic music is the Next Big Thing, just in time for the millennium. Many of you reading this magazine will say that electronic music never really went away — it just got absorbed into Dance, Trance, Ambient, Electronica and all their mutant hybrid variations. But if, like me, you enjoy making electronic music the old‑fashioned way, by patching and twiddling banks of knobs, the Analogue Systems RS Integrator modular synthesizer is like manna from heaven — controls and sockets galore!

Before I get into the meat of this review, it's worth directing anyone who is not familiar with modular synths to the helpfully titled 'What is modular synthesis?' box on page 110. Those who already know their Inverters from their Voltage Quantisers may read on...

Bursting At The Seams

Following a growing trend, Analogue Systems have designed the RS Integrator around a standard Eurocard Sub‑Rack system, with two types available: the 3U‑high RS10 and 6U‑high RS15. Each 3U case will hold six or seven modules, depending on size. In theory, this means that you could install additional synth modules made by other manufacturers conforming to the same Eurocard width standard (see 'Building And Expanding' box). Currently, around 20 different modules are available from Analogue Systems, with another seven or so in various stages of design and production.

For this review we were supplied with two racks bursting with modules. The first is a standard RS Integrator 'off the shelf' configuration called System 1, comprising:

• RS15 case
• RS90 VCO (x2)
• RS100 VCF
• RS110 Multi‑mode VCF
• RS180 VCA (x2)
• RS60 ADSR (x2)
• RS80 VCLFO
• RS20 Ring Mod/Multiple jack link
• RS40 S&H/Noise/Clock
• RS160 Mixer (Lin)
• RS160 Mixer (Log)
• RS230 CV Buffer
• RS170 Multiple jack link.

The second rack we were supplied with is a customised unit comprising:

• RS10 case
• RS30 Pitch‑Voltage/Envelope Follower
• RS70 Pre‑amp/Inverter
• RS50 Trigger Generator
• Pulse Shaper/Level Shifter
• RS80 VCLFO
• RS110 Multi‑mode VCF
• RS210 Filter Bank

Living In A Box

The Integrator modules and racks have a slightly unfinished look about them, being plain brushed aluminium with black screen printing, smallish 'soft feel' knobs and mini‑jack sockets throughout. To assist with programming, the knobs are colour‑coded: white for audio/signal paths; grey for CV/control; blue for frequency/clocks; red for ADSR; green for waveshape/width; yellow for res/slew/pan; and orange for anything else. A set of similarly coloured patch cords is supplied with each system, which is a nice touch. Both the RS10 and RS15 system cases include a built‑in power supply with power input socket and mains switch on the rear panel (which could be an annoyance if the unit were mounted in a rack or transit case). Overall, construction quality is high, everything feels solid and well built, and the units would probably take life on the road quite easily. However, I'm not sure I like the current vogue for aluminium with a semi‑industrial appearance — it looks a little cheap to me.

Block By Block

Because of the number of different modules that can make up an RS Integrator system, I won't be describing every single feature of every single module (and some functions are quite self‑explanatory anyway), but I will try to give as much detail as I can on the most relevant modules. Unfortunately, an instruction manual wasn't available for the review, so I had to make the odd educated guess or resort to my ageing oscilloscope for some of the specifications.

One feature common to both the VCF and VCA modules in the Integrator system is the inclusion of two audio inputs, each with a level‑control knob. This is welcome, as it cuts down on the need to feed signals into the mixer module first, which would just add to the number of patch cords hanging around (literally). Also, most of the CV modules have a direct 1V/Oct input (for keyboard or sequencer) and a variable CV input with level knob (for modulation).

RS90 VCO

Currently, Analogue Systems only produce one VCO module, but it contains most of what you'd expect to find, plus a few surprises. There are five controls (Frequency, CV input level, Waveform shape, CV input (X2), and Range) and five inputs (1V/Oct in, Variable CV in, Square wave shape CV in, Sawtooth shape CV in, and Sync in). The sawtooth output shape can be adjusted from a rising ramp, through a triangular waveform, to a falling ramp. The sawtooth shape is voltage controllable, as is the square wave shape, and some nice fattening effects can be achieved by modulating these two independently. The range of the VCO is a respectable 0.3Hz to 17kHz (about 20 octaves) and I found it to be stable, with no drifting.

Next to the Frequency knob is a 3‑way switch for Wide, Tune or ‑2 Oct. At the Wide setting the frequency can be swept in one continuous turn (a nice touch), while the Tune position allows the VCO to be fine‑tuned by approximately a fifth. The ‑2 Oct control is similar to the Tune control, but also reduces the pitch by two octaves. In its lower ranges, the VCO can be used as an additional LFO (Low Frequency Oscillator). There are control inputs for 1V/oct (for keyboard or sequencer) and variable CV (for modulation), and a Sync input is also available for resetting the cycle of the waveform to another VCO signal, to get those great edgy lead synth sounds.

RS100 Low‑Pass VCF

Unlike most VCFs made in the last 10 or 15 years, which are usually designed around Curtis chips, this filter uses a traditional Moog design, the so called 'ladder' resistor type. While this may not be a bells and whistles, state‑of the‑art filter, it is, according to the designers, about as close to a Moog filter as you can get without buying a Moog. Controls are kept to a minimum and comprise only Frequency, Resonance, and input‑level controls for audio and CV signals. There are no fancy features — this is just a bread‑and‑butter low‑pass filter. But what a filter! The sound is what you might call sweet with musical overtones, and, I must admit, very 'Moog sounding'. By my measurements, the frequency response isn't as wide as some other filters (including Analogue Systems' own RS110) but who cares when a VCF can sound as sexy as this? Feed it with a couple of VCOs and the world is your lobster — beautiful bass lines, screaming lead lines, growling pulses, resonant saws... You name it, this filter can handle it.

RS110 Multi‑Mode VCF

This is an extremely versatile filter with four simultaneous outputs: Notch (phase), Band‑Pass, High‑Pass, and Low‑Pass. The frequency range is approximately 20Hz‑20kHz, and with the resonance control turned fully clockwise the filter self‑oscillates and turns into a very nice sine wave VCO. Where you might normally expect to find a voltage‑controllable resonance, this filter instead has a unique separate resonance output with a corresponding resonance input. This is an 'insert' point in the resonance path which allows you to send the resonance signal to an external modifier, such as a filter bank, second VCF, VCA, or even a delay line or effects unit. The results can be quite exciting and can change the characteristics of the filter pretty dramatically, and sometimes a little unexpectedly. An eye has to be kept on the position of the Resonance knob when using some configurations, as it's quite easy to overload the VCF, but once you've tried this unusual feature you tend to find yourself thinking of more and more devious routes for the resonance to take. The overall character (or timbre) of the filter falls a little short of the RS100, but that's just a subjective impression, and considering how talented the RS110 is, this slight failing is forgivable.

RS180 VCA

Like the modules above, this is another essential 'building block' module. Apart from audio and CV input level knobs, the only other control is for Initial Level. This control lets you add an offset voltage to the CV inputs, which 'opens' the VCA output and allows you to hear an audio signal even if no other control voltage is present. Interestingly, this VCA allows for both Linear and Logarithmic voltage control simultaneously. Rather than getting bogged down in explaining the theory of Log/Lin control, I'll just say that Log inputs sound better with dynamic voltage‑control signals such as ADSR envelope generators, while Linear inputs perform better with traditional CV signals such as LFO waveforms and keyboard voltages.

This VCA performs as you'd expect — cleanly and transparently, with no artifacts. Also bear in mind that it's quite happy handling control voltages through its two audio inputs, which can allow for some complex mixing and controlling of CV signals from other CV sources.

RS60 ADSR

This envelope generator has the usual Attack, Decay, Sustain and Release knobs, plus an output level knob. This is adjustable from normal output (+V), though zero (centre position) to inverted output (‑V). There are two 3‑way function switches: one provides Hold, Standard, and One Shot triggering options, while the other activates a very useful built‑in trigger LFO whose options are Gated Repeat, Standard, and Auto Repeat. In Gated or Auto Repeat mode the internal LFO rate is adjusted by the Release knob, and if the switch is in the Auto position the LFO constantly triggers the ADSR function. If it's in the Gated position, the LFO only triggers the ADSR when an external control signal is present at the gate/trigger inputs. An LED shows the rate of the LFO or the presence of an external gate/trigger. I haven't seen a facility like this built‑in trigger LFO since the EDP Wasp. It's a brilliant little featurette and makes it dead easy to set up funky, syncopated triggering effects when using the ADSR with a sequencer or another LFO.

The RS60 ADSR also has a voltage control option which, while welcome, is a bit limited, as it only offers simultaneous control over Decay and Release time.

RS80 Vclfo

Regular readers of SOS might know of my love of LFOs — you can never have enough of them, I say. This one is pretty well specified, with a frequency range that extends from sub‑sonics into audio (0.02Hz to 1.4kHz, in two ranges), and an LED indicating the LFO rate. There are four waveforms (sine, triangular, square, and a variable sawtooth, with rising or falling ramp). All are available simultaneously and all except the sine have output‑level controls. The waveforms don't exhibit any uneven swings or lumpiness, and the LFO sounds perfectly stable. It's worth noting that although the RS80 doesn't use a 1V/Oct CV input it will track a Hz/Volt CV signal, which could be useful if you have an old Korg or Yamaha analogue synth.

A Reset input allows you to sync the LFO waveform cycle to keyboard or sequencer trigger control, or, alternatively, lets you sync it to a VCO. With the right settings the LFO can track a VCO over a wide range, making it a perfectly serviceable audio oscillator. It would be nice if a variable delay was included (for fading up the waveform), but this is an effect that can be patched together with a spare ADSR/VCA.

RS20 Ring Modulator/Multiple Jack Link

There are no controls on this module — just sockets and a great sounding ring modulator. As is usually the way with ring modulators, it's tempting to do all the clichéd effects — Daleks, metallic sounds, FM‑type stuff — but this module also tolerates control signals and, unlike some ring modulator designs, responds well to slow‑moving control voltages, to produce classic 'bowing' effects of the type which are characteristic of the vintage EMS VCS3 synth. This is logical, because the RS20's design is based on the type used in EMS synths. Another interesting 'scrambled' effect can be achieved by feeding a complex signal (such as a guitar, MIDI synth, or even a mix) into both inputs simultaneously. But I must admit to being mildly disappointed with this module, as it has only one ring modulator section and four interconnected mini‑jacks, for making multiple connections from one connection, extending links when your patch cords are not long enough, and so on; personally I think they should have included two ring modulators and left out the extra sockets.

RS40 Noise/S&H/LFO

This is another useful module, containing a white noise generator, which produces a basic white noise signal at control level, with a single knob for output level (to get other types of noise, sometimes referred to as pink or red noise, you'd need to feed the noise signal into a VCF or filter); a Sample & Hold circuit with an external source input, a One Shot push button and an output level knob and socket; and an LFO/clock, which produces a basic square wave output (with LED and Rate knob) covering a few Hz. I must admit to a few minutes of initial head‑scratching with this module. Usually (in my experience) a Sample & Hold circuit would be internally connected to the noise generator and LFO/clock, to produce a random CV signal as a default setting without any patching. However, to produce any meaningful results with this module you need to patch the noise generator output into the S&external source input and the LFO/clock output into the external clock input. This patch produces a basic, stepped random voltage at a rate set by the LFO/clock. However, you can substitute the noise signal with any control voltage and the internal clock signal with any LFO or gate‑type control.

RS70 Inverter/Preamp

This module is used primarily for interfacing with the outside world. The Preamp section has a low‑level input suitable for microphones and guitars, and a high‑level input for line signals, though line‑level signals can also be fed into the low‑level input for overdrive effects. The Inverter section is unusual because it performs different functions according to whether the input is an audio or control signal. There are two control knobs, labelled Level and Slew. When used with an audio signal, the Level knob's null centre position mutes the output. Turning the knob clockwise results in a normal but boosted audio signal (maximum gain x10), while turning it anti‑clockwise produces an out‑of‑phase signal. In this context, the Slew control acts like a simple low‑pass filter and attenuates any high frequencies. If a control voltage rather than an audio signal is passed through the Inverter, the Level knob allows the signal through unchanged in the null position, boosts it when the knob is turned clockwise, and boosts and inverts the voltage in the opposite direction. This function is useful for phase reversing LFO waveforms, for panning‑type effects, and for inverting sequencer notes (although you can achieve a similar function using the RS230 CV Buffer module, which also contains an inverter). When it's used with control signals, the Slew knob slows down (or smooths out) the changes between stepped voltages, and is handy for adding glide or portamento to a keyboard or sequencer CV signal.

RS30 Pitch‑To‑Voltage & Envelope Follower

Like the previous one, this is another module for interfacing with the outside world. The envelope follower works by analysing an input signal and producing an envelope control‑voltage based on the amplitude of the signal. It works well with most sources, but I found that regular audio signals (off‑tape, guitar, mic, sampler, and so on) needed to go through the Preamp module first, to get a decent drive level. A useful Slew knob allows transient signals to be smoothed out, but I would like to see an LED to show when an input and/or output signal is present.

Don't expect too much from the Pitch‑to‑Voltage section of this module: it's basic, functional, and monophonic. To get any sort of usable results you need to feed it a non‑complex, monophonic signal (otherwise the results will be random gibberish) and patch the control output signal into a VCO CV input. When I used the Pitch‑to‑Voltage facility to follow a VCO square wave signal, it tracked over approximately half an octave before drifting out of tune, but it fared better when fed a basic four‑note synth bass line.

RS50 Trigger Generator/Vc Pulse Shaper/Dc Level Shifter

With this module, things start getting a little esoteric, and Analogue Systems inform me that they have plans for more weird modules in the future.

The Pulse Shaper can take a signal (audio or control) and produce 10V gate pulses derived from the peaks and transients the signal contains. This works well, and is useful for syncing analogue sequencers and envelope generators to bass lines, drum machines, or other sequencers. It also features a knob for varying the pulse (gate) width and a voltage controllable pulse‑width input.

The Level Shifter section is for transposing CV or trigger/gate signals by +/‑10V, using a variable control where the centre null position allows the CV signal through unaffected. The Shifter also produces a +/‑10V control voltage output without any input signal present. This could be useful for manually sweeping or controlling multiple CV sources simultaneously from one knob.

The Trigger section is one of the most innocuous‑looking parts of this whole system, with just an input socket, output socket, and an LED. Yet it's capable of performing all sorts of weird and wonderful functions. Its primary purpose is similar to the Shaper — to output a 10V trigger pulse from an input signal, which it does admirably. However, while the Shaper literally strips out the input and replaces it with a series of on/off trigger pulses, the Trigger works by detecting pitch changes in the signal, with altogether different results. Its input doesn't have to be audio, either, as it can detect changes in CV signals also — such as keyboard and sequencer patterns or joystick movements. When you feed in a complex audio source and monitor the control output as if it were an audio signal, the control output 'adopts' (for want of a better word) the characteristics of the input signal. The sound is like a cross between a ring modulator and a fuzz box. Because there are no controls for this section, you need to use a pre‑amp or a source with a variable output level to get manageable results — the slightest change in level can dramatically alter the sound. I had great fun trying out different sources, including tapes, samples, bass lines, and drum machines, and I got some outrageous effects. Taking things a step further, some interesting results can be achieved by feeding the control output into other voltage‑controllable sources and modifiers.

According to Analogue Systems, the Trigger can also operate as a frequency doubler, and you can plainly hear this effect if you use the right input levels on some audio material. One of their suggestions is that it could be used to transpose a Sync24 drum machine clock signal to 48ppqn (pulses per quarter note) to drive some older drum machines, although I wasn't able to check this out). Experiment!

RS160 4:1 Mixer

There are two types of mixer: Log for audio signals, and Lin for control voltages. You're not restricted to how the mixers are used, though — control voltages can be put through the Log mixer and audio through the Lin mixer. Each mixer has unity gain and a variable master output capable of producing positive or negative signals, with a null point in the centre position.

RS210 8‑Octave Filter Bank

This is a basic, single‑channel, no‑frills affair, with eight fixed bands at 75Hz, 150Hz, 300Hz, 500Hz, 700Hz, 1.5kHz, 3kHz, and 7kHz. The eight knobs simply attenuate, or pass through (without boosting) each band.

Other modules include the RS230 CV Buffer, which is used to distribute a single CV or gate signal to multiple sources and offers an inverted output, and the RS170 Multiple, which consists of two rows of five interconnected mini‑jacks.

Spaghetti Loops

I find little to complain about with the RS Integrator. I'd like to have seen an input‑ and/or output‑level LED on some of the modules (as on the venerable Roland System 100M modular synth), to help the user track down signals and rogue levels. I'd also like a few more options on the VCO, such as a sine wave output and a soft/hard option for the sync input. A few more octave steps for frequency range would be useful, as would a separate fine‑tune control, and for really complex modulations, a third CV input wouldn't go amiss either.

Including only one Ring Modulator in the RS20 module is a bit mean, and I also expected to find some form of common buss system to assist in sending keyboard CV, gate and trigger signals to modules such as the VCO, VCF and ADSR, as this would cut down on using patch cords unnecessarily.

Comparisons between the RS Integrator and Doepfer's A100 modular system (see p.12, SOS November '97) range are inevitable, as these are the main new modular systems on the market at the moment. And I'm sure it must have crossed a lot of people's minds that the RS Integrator and Doepfer 100 system look spookily alike. Well, they would, because they're based around the same rack case, and if this means the beginning of a new 'standard', that's probably a good thing. (Incidentally, the Roland System 700 and Moog Series 3 looked almost the same, but their modules weren't interchangeable.)

Euro Synth

The custom system supplied for review here will set you back about £1450 (including VAT). However, try buying an equivalent, second‑hand, 22‑module Roland 100M system and you'd probably have to pay in the region of £2500 or more. I'm not even going to consider the cost of a similar Moog, ARP or Roland System 700! (When compared to a Doepfer system using similar modules, the RS Integrator works out slightly cheaper, partly due, no doubt, to the fact that Doepfer modules have to be imported from Germany.)

On the whole, this is a superb analogue modular system — well designed, full of comprehensive features, solidly built, expandable, and reasonably affordable. Even the basic Mini System (see 'Systems' box) should be capable of producing some pretty complex sounds; at £595 it's competitively priced (though no MIDI‑CV interface is included) and makes a good place from which to start building a larger system. The oscillators are wide‑ranging and stable, and the filters are particularly well specified for this price.

The RS Integrator may not be the best choice for beginners or 'MIDI heads', but if you're an analogue purist, or analogue appeals to you and you're not too intimidated by all those knobs and sockets, it's definitely worth considering. Instruments like this also make extremely useful teaching tools because of the very graphic and obvious way signal paths and connections can be seen and implemented. Modular synthesis is, after all, what many electronic instruments are in basic form — a collection of sources, filters, modulators, modifiers and controllers. The only problem with the RS Integrator could be availability, as Analogue Systems are selling them as fast as they can make them. If I were you, I'd place my order now.