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Cwejman Sound S1 MkII

Semi-modular Analogue Synth By Gordon Reid
Published August 2004

Cwejman Sound S1 MkIIPhoto: Mark Ewing

Swedish company Cwejman have recognised that there's no way to build a cheap semi-modular analogue synth for mass-market sale these days — if there ever was. Enter the premium, but meticulously crafted S1 MkII...

It's not often that SOS gets to review Swedish semi-modular analogue synths designed by Polish engineers, but improbable as this may seem, the S1 MkII is one such product. The Polish engineer in question, Wowa Cwejman (pronounced, I'm told, 'Vohva Svymen'), first began designing analogue synths in the early '70s, although these never became commercial products. During the '90s, following the revival of interest in all things analogue, Cwejman applied himself to developing a commercially viable analogue monophonic synthesizer, drawing upon his 20 years of industrial engineering experience to improve upon his earlier ideas. The result was a unit that looked and felt more like a piece of equipment from a large corporation than the home project that it was.

It took several years for Cwejman to find manufacturing facilities in Sweden (his adopted homeland) which met his exacting construction standards, and the initial release of the S1 in 2003 was followed by a design re-think. Nonetheless, the S1 MkII has finally arrived, and it seems it was worth the extra trouble — you only have to look at it to know that it's a serious piece of kit.

Getting Started

The S1 is a 5U module, painted in battleship grey, and is supplied with a pair of full-length rack ears so that you can mount it in a conventional 19-inch rack. This is just as well, because a wide range of inputs and outputs on the rear (including the mains power input) mean that you can't use it as a desktop unit.

The rear panel should be the first port of call for anybody using the S1. Alongside the standard IEC mains socket, there's a voltage selector, and you must check how this is set before switching on. The S1 incorporates a universal power supply that accepts 115V or 230V, and 50Hz-60Hz mains power, but the switch must be in the correct position, or something may go 'bang'. To the left of these, you'll find two audio outputs. One is a balanced XLR output. The other — which carries the same signal, and is duplicated as a 3.5mm socket on the control panel — is an unbalanced output carried by a standard quarter-inch jack socket.

The S1 MkII's power supply is capable of running off different voltages, but the required one has to be set on the back panel manually. Note also the balanced XLR output on the left — another example of Cwejman not doing things by halves.The S1 MkII's power supply is capable of running off different voltages, but the required one has to be set on the back panel manually. Note also the balanced XLR output on the left — another example of Cwejman not doing things by halves.Photo: Mark EwingTo the far right of the rear panel lie the MIDI In/Out/Thru, together with a four-way DIP switch that allows you to select the main MIDI channel to which the S1 will respond. Underneath this switch lies an LED that lights up when a MIDI message is received. This is a curious place to position the LED since, in normal operation, nobody will ever see it!

The centre of the rear panel is dominated by four analogue inputs and 10 analogue outputs derived from the incoming MIDI signal. The inputs comprise the expected 1V-per-octave pitch CV, Gate and Trigger, plus the unexpected bonus of S-Trig for die-hard vintage Moog aficionados. The outputs are CV1, CV2, CV3, CV4, Master (pitch CV), Gate1, Gate2, Trig1, Trig2, and S-Trig, which we'll discuss in greater depth below. In addition, there are eight calibration trimmers that allow you to adjust the range and scale of each of the oscillators, as well as the range and scale for the synthesizer as a whole. As shipped, the review S1 was perfectly set up, and did not drift. If you need to tune yours, the calibration procedure is included in the manual.

Having connected power, a MIDI In (or CV/Gate if you prefer) and a signal output, you're ready to return to the front panel. The upper three-quarters of this is densely populated with 59 knobs and more switches than I care to count, but avoids appearing cluttered through a clever choice of layout and legending. For example, all the CV outputs are revealed by a red surround. Similarly, where a CV input is pre-patched internally, its source is shown by a red legend inside a white box. These little touches make the S1 far more comprehensible than it might otherwise have been. I suggest you refer to the full front-panel picture at the end of this review to locate the various controls and connections I'll be describing throughout this review.

The S1 also boasts dozens of 3.5mm patch points arranged along the lower part of the panel. This is a neat arrangement previously used on the mighty Korg PS3200 and, although it means that sockets are positioned away from the knobs and switches that control their functions, it's a boon when the S1 is mounted vertically.

Yet, despite its patching capabilities, the S1 is not a modular synth; it is semi-modular. This means that all the internal units are connected in sensible ways so that you can obtain conventional sounds without using patch cables. Some people have compared it to the MS20, but that's not a fair comparison; the Korg is far too limited for this to make sense. Comparing it with the ARP 2600 is more realistic, both in terms of flexibility and complexity, but there's only one synth to which I think I can truly compare the S1, and that's the Synton Fénix, which was even more flexible than the the S1, but had no internal patching, and was less intuitive in use.

MIDI Matters

The S1's MIDI interface was not included in the original design by Wowa Cwejman, and when an interface was first added, it had a basic specification. The one included in the S1 MkII is well specified, but the relative complexity of editing its functions betrays its origins as a late addition to Cwejman's design.

I'll start my tour of the facilities on offer in the Master CV section, where three switches and four sockets determine the action of the envelopes and, therefore, the response of the instrument to MIDI Note On and Note Off messages. At first sight, these are far from intuitive, because Cwejman have designed the S1 to respond to not one, but two MIDI channels; the selected MIDI channel and the one numerically 'above' it (so if the selected receive channel is 4, the S1 also responds to 5).

Things start simply enough; the Gate generated by the main MIDI channel is hard-wired to EG1. This means that, whenever you play and hold a key, EG1 will progress through its Attack and Decay stages, and then sit at the Sustain level, as normal. However, if you want to retrigger EG1 while the Gate is present, you must set the appropriate switch, which determines whether an EG1 trigger is generated by the main MIDI channel, the next channel 'above' it, or not at all. Setting this to position '1' (the main MIDI channel) means that each new note will be retriggered and articulated, even if you play legato or overlap notes. However, if you set it to 'Off' or to position '2' (the next MIDI channel 'up' from the main one), you can play legato without retriggering. To be fair, there are other synthesizers that offer independent triggers and gates, but none that I can recall allow you to separate them in this fashion.

Alongside the EG1 trigger switch lie two others. The first of these determines whether EG2 is Gated by the main MIDI Channel or the one 'above' it, while the third determines whether EG2 is also Triggered by the main MIDI Channel, the next channel up, or neither. All of these Gates and Triggers are accessible from the rear panel as CVs, and you can also override them by presenting signals to the four Gate and Trigger inputs at the bottom of the Master CV section.

Although complex and initially confusing, this architecture is rather useful, especially when used creatively with the envelope routing and mixing options. Cwejman suggest that you use the second Trigger+Gate pair to create rhythmic patterns that overlay your playing, but this is only one possibility.

The key priority is set within the MIDI-CV converter, and this proves to be last-note priority with an interesting twist. When a new note is pressed, the new pitch CV is generated, a Gate is generated, and a Trigger pulse is sent out. However, if a previous note is still held when you release the new note, the pitch CV reverts to the previous note and another trigger is generated so that the previous note is re-fired in its entirety. Up to five notes — all with pitch CV, Gate1, Gate2, Trigger1 and Trigger2 — are stored in the converter's memory, making the S1 extremely playable. Fast runs and arpeggios sound far more competent when played on a synth of this nature, and briefly clipped wrong notes become the correct ones when you release them.

Above the Trigger and Gate input sockets, you'll find a row of output sockets that provide four MIDI-generated CVs. These are CV1 (master pitch), CV2 (Note On Velocity), CV3 (continuous controller #1, or mod wheel), and CV4 (channel aftertouch). There are two further CVs derived from the MIDI signal, but these are not accessible from the panel. The first of these, CV5, is pre-programmed for continuous controller #5 (portamento time), while the second, CV6, is pre-programmed to respond to the pitch-bend wheel.

The six CV functions are well chosen, and I can imagine most users being happy with these. Nonetheless, the S1's MIDI-CV converter is programmable, and you can replace the CV2, CV3, CV4 and CV5 functions with others, such as breath control. Unfortunately, the method for resetting the MIDI behaviour requires intimate knowledge of NRPN Coarse and Fine messages, and the system is so arcane that I expect few players to attempt it, especially since the manual contains a number of errors and omissions that make it even harder to work out what's happening.

As explained above, this is due to the way in which the MIDI features of the S1 developed later than the rest of the synth. By the time the fully featured MIDI interface was added, there was no front-panel room left to give it physical controls, and so Cwejman have settled for the NRPN control system that the S1 MkII suffers today.

The S1's PC-based MIDI Editor, with CV4's Function Select menu open.The S1's PC-based MIDI Editor, with CV4's Function Select menu open.

The company clearly recognise that the control system is arcane as it stands, as they have now released a PC-based MIDI-CV editor for the instrument. This makes system configuration easier, but there are no plans for a Mac version, which is a shame. Ultimately, I think that it's a bit naff being unable to access all the S1's facilities from the S1 itself, and I predict that the vast majority of Cwejman owners will ignore the programmability of the MIDI interface as a result.

Oscillators & LFO

The S1 boasts three audio oscillators, of which one (Osc1) can be switched to perform low-frequency duties. Each oscillator offers seven waveforms: sine, triangle, sawtooth, saw+triangle, pulse+triangle, saw+pulse, and variable-width pulse, with a nominal duty cycle range of 5 to 95 percent. The pulse wave responds to pulse-width modulation in all three of the waves to which it contributes, and in the pulse+triangle and saw+pulse waves you can modulate it to 0 percent at one extreme and 100 percent at the other to reveal the unadulterated triangle and sawtooth waves. In other words, these are true mixes of the component waves, not approximations generated by waveshaping.

Each oscillator offers fine-tuning of ±6 semitones, and a range control that allows you to shift it across seven octaves, from the equivalent of MIDI note C2 to MIDI note C8. The only difference between the oscillators is that in low-frequency (LF) mode, the range control can also shift Osc1 from approximately one-eighth of a Hertz to 8Hz.

Where Osc1 has its LF switch, Osc2 and Osc3 offer 'sync' switches that hard-sync them to Osc1 and Osc2 respectively. To the right of these, each oscillator also has a Frequency Modulation Level control. On Osc1, this is internally patched to the LFO for conventional vibrato duties, but on Osc2 and Osc3 they are patched to Osc1 and Osc2 respectively. Given that you have seven waveforms as starting points, and five sync and FM routes, the flexibility afforded by this arrangement is enormous.

This is a convenient point to introduce the Master CV Controller section, because it determines the response of the oscillators to incoming signals. At the top of the section, you'll find four easily understood controls: the master Modulation Level (which is pre-patched to the LFO), Glide, a Master Transpose with a range of ±3 octaves, and a Master Fine Tune of ±3 semitones.

Next, you come to six small switches, three of which disconnect the audio oscillators from the incoming pitch CV. These are useful if you want to use the VCOs as controllers, modulators or carriers that do not track the pitch as you play up and down the keyboard.

Below these lie three CV inputs, one each for Osc1, Osc2 and Osc3. As shown by the legending, and as demonstrated by the FM depth controls described above, these are pre-patched to the LFO, Osc1 and Osc2 respectively. This, however, is where you can break the internal patching and insert any new modulation signal of your choosing. Alongside these, there's a fourth input which allows you to disconnect the LFO from the master Modulation Level and insert another signal.

Safely tucked away at the back of the S1 MkII, in addition to the CV inputs, the three MIDI ports and the CV output jacks from the MIDI-CV converter, are various 'set and forget' switches, such as the calibration pots for the Oscillators, Master Scale, and main CV input, and the four-way DIP switch with which the receive channel for the built-in MIDI interface is adjusted. Thoughfully, the 16 possible combinations are silk-screened onto the panel, so you don't have to go hunting through the manual if you ever want to change the main MIDI receive channel.Safely tucked away at the back of the S1 MkII, in addition to the CV inputs, the three MIDI ports and the CV output jacks from the MIDI-CV converter, are various 'set and forget' switches, such as the calibration pots for the Oscillators, Master Scale, and main CV input, and the four-way DIP switch with which the receive channel for the built-in MIDI interface is adjusted. Thoughfully, the 16 possible combinations are silk-screened onto the panel, so you don't have to go hunting through the manual if you ever want to change the main MIDI receive channel.Photo: Mark Ewing

This is not the end of the possible connections you can make to the oscillators. If you look at the bottom centre of the S1, you'll find a panel marked Level/PWM CV, and the six sockets presented here allow you to affect the oscillator output level and pulse width of each oscillator. This sounds simple enough, except that two of these — the Osc1 PWM input and the Osc2 PWM input — are pre-patched to the outputs from the CV Mixer. This is a two-input, two-output mixer with level controls for the input signals. The pre-patched inputs are the LFO triangle wave and the output from Envelope Generator 1, but you can override these by inserting patch cables into the associated sockets. The two outputs (which, as just mentioned, are pre-patched to the PWM inputs of Osc1 and Osc2) are the sum of the attenuated inputs, and an inverted version of the same signal. You can direct the output CVs to any input of your choice, but it's not hard to see why these choices were made. With input level 1 at a non-zero value, but level 2 at zero, the mixer outputs the LFO in positive and negative polarities. Directing these to the pulse width of the two oscillators then sweeps them in opposite directions, which offers some pleasing sonic possibilities.

Directly above the CV Mixer, you'll find the first half of the LFO. This has a wide range of approximately one-sixtieth of a Hertz to 60Hz, which means that it is capable of generating sweeps lasting a minute... if you can be bothered to wait that long to experience them. An LED gives a visual indication of the LFO rate, and its brightness tracks the shape of the LFO waveform. However, it was while watching this — without any modulation depth being programmed into the sound — that I noticed something strange: the LFO triangle and square waves run at half the frequency of the other five waves (which are sawtooth, ramp, S&H, slewed S&H, and even more slewed S&H). I can't remember having encountered this LFO behaviour before, and I'm not sure what use it might be, but I'll give Cwejman the benefit of the doubt, and assume that this was the result of a decision, not just engineering expediency.

The other half of the LFO lies below the CV Mixer. This comprises a 1V-per-octave frequency control input, an amplitude CV input, plus a Gate input with an associated switch that allows you to 'sync' the LFO waveform to MIDI Gate1, MIDI Gate2, or an input CV. Oh yes... and there's also an output. The sync option is interesting, not just because it allows you to reinitialise the LFO wave, but because it allows you to direct the LFO output back into itself as the sync source, which leads to some interesting chaotic effects.

The DC-coupled ring modulator is another section related to the oscillators. The manual tells you that the signal inputs are pre-patched to the sine waves generated by Osc1 and Osc2, while the legending suggests that they are those generated by Osc2 and Osc3. The panel is correct! A third input affects the output level of the modulated signal, and the output socket allows you to direct the result elsewhere. I would have preferred the RM to be AC-coupled, because this guarantees that the input signals are eliminated from the output, but there appear to be no DC offsets in the input signals, so the same result ensues.

If you want to tap the oscillators' signals directly, there's an output panel that offers individual outputs from each, as well as three noise signals: white, red, and 'low', which is a random signal much like a slewed S&H. However, it is far more likely that you will want to combine the signals in the two mixers that determine the inputs to the two filters...

Filter-input Mixers

The S1 offers two filters. One is called the Low-pass filter (or LPF — but this, as we shall see, does not tell the whole story) and the other is the MMF, or Multi-mode Filter. Each filter has five audio signal inputs. As pre-patched, the five for the LPF are Osc1, Osc2, Osc3, the RM, and the output from the MMF. The five for the MMF are Osc1, Osc2, Osc3, the Ring Modulator, and White Noise.

Each level control is calibrated from zero to 10, with nine of them showing the figures '9' and '10' in red. This indicates that, at these levels, this signal is overdriving the relevant filter's input stage. You can also reach saturation by using multiple inputs of lesser level. The exception to this is the MMF input to the LPF, which saturates at just '7' and upwards (again, the manual shows this incorrectly, but it's a minor point).

You'll find a small panel with two sockets lying underneath the control strip for each filter. On the LPF, this includes an high-impedance audio input that allows you to input an audio signal in place of the output from the MMF. The MMF knob in the LPF mixer then controls the external signal level. Likewise, the MMF has a socket that replaces the pre-patched white noise with another signal of your choice, whereupon the White Noise knob in the MMF Mixer controls its level. The second socket in each of these panels is a filter output, thus allowing you to direct the filtered signal to destinations other than the pre-patched VCA input.

The Filters Themselves

I've already hinted that the LPF is misnamed. This is because it actually offers three modes, four-pole (24dB-per-octave) low-pass filter, six-pole (36dB-per-octave) low-pass filter, and four-pole (12dB-per-octave high and low) band-pass, the last of which is obviously not a low-pass topology. The cutoff frequency knob allows you to determine the cutoff (or, in band-pass mode, the centre frequency) from a claimed 16Hz to a claimed 16kHz. The Q-Peak knob below it varies the filter resonance from flat to self-oscillation. The resulting oscillation is close to a sine wave, and sweeping this through a signal analyser demonstrates that the range of the LPF's cutoff frequency is actually 9Hz to more than 22kHz.

There are three LPF cutoff frequency-modulation knobs. These allow you to control the cutoff frequency using the output from EG1 with either positive or negative polarity, the output from EG2 with either positive or negative polarity, and the selected LFO waveform and rate, or the triangle-wave output from VCO1. The first two of these will sweep the cutoff frequency through its full range of 10 octaves, in either polarity. The third sweeps it by ±5 octaves. Either way, this is a far greater range than you should ever need.

You can extend the LPF's patching using three CV inputs at the bottom of the filter strip. The first of these affects the cutoff frequency, and replaces the pre-patched Osc1/LFO input, allowing you to use the Osc1/LFO knob to control the level of any external signal you present to this input. The second controls the gain of the signal(s) being filtered, but appears to have its effect at the filter's output, because it has no effect on the overdrive/saturation at the filter input. The third affects the filter resonance. Bravo... voltage-controlled resonance!

The MMF is the more flexible of the filters, offering two-pole, four-pole and six-pole slopes (12dB-per-octave, 24dB-per-octave and 36dB-per-octave) in both its low-pass and high-pass modes. It applies the same filter stages in band-pass mode, offering high and low slopes of six, 12 and 18dB per octave. In all other respects it is identical to the LPF except that its bandwidth extends from less than 3Hz to more than 22kHz. Whether this is a full amplitude response, or whether it is attenuated at such extremes, I can't say, but these are remarkable results by any standards.

Both filters have controls in the Master CV section. The two knobs control the cutoff frequency tracking, and allow you to set the filters to track the master pitch CV from 0 percent to 200 percent. Each filter also has a switch that, as well as an 'Off' position, allows MIDI CV3 (mod wheel) or MIDI CV4 (aftertouch) to affect the cutoff frequency.

Envelopes & VCA Stage

Next come the two envelope generators. These are five-stage devices, each with a Delay before the ADSR contour. The minimum Attack, Decay and Release times are quoted as 500µs which, if true, is astonishingly rapid. The minimum Delay is quoted as 1ms, which — since you cannot remove it from the equation — slightly takes the shine off the Attack figure, but in no way detracts from the 'snap' of the envelope when it opens. The maximum time for each of the envelope stages is 20 seconds.

Each EG has two outputs: positive and negative, the first of which are directed to an Envelope Mix control just below the VCA itself. This allows you to mix the two contours in any proportion from 100-percent EG1 to 100-percent EG2. What's more, a switch allows you to toggle between a linear envelope mode (20 percent of full range per volt) and a logarithmic mode (15dB per volt or 16dB per volt, depending upon which bit of the manual you believe). These make it possible to create some complex contours, especially since you can delay the onset of one envelope with respect to the other. What's more, each of the envelope stages has CV-input sockets, and there's even a level CV for each contour, making a total of 12 envelope CV inputs. This is stunning stuff.

The VCA itself has two pre-patched inputs, these being the outputs from the LPF and the MMF. However, in line with the philosophy employed elsewhere, you can remove the LPF from the mix by presenting an external signal to the Ext Input socket. You balance the contributions from the MMF and the LPF/External signal using the Filter Mix control, and determine the loudness using the Output Level control.

The final knob on the S1 is the VCA Overdrive, which acts as a distortion control, modifying the signal from clean at one extreme, to heavily boosted and clipped at the other.

Below the VCA, you'll find a single socket and a switch. You can direct any signal to this socket, but it is pre-patched to MIDI CV2 (MIDI velocity) and when the switch is 'On', this makes the amplifier velocity-sensitive. This introduces us to the S1's MIDI interface, which you can read more about in the 'MIDI Matters' box on page 106.

In Use

In the weeks that I have had the S1 to hand, I have never veered from two conclusions. Firstly, the thing is astonishingly flexible, offering more potential than almost any other monosynth, particularly when you take advantage of its patching capabilities. Secondly, it may be compact, but it is sonically a heavyweight synthesizer, with a ballsy sound.

In addition, it has a character that sets it apart from other 'serious' synthesizers such as the Minimoog, the OSCar, the Crumar Spirit and so on. The difference is hard to quantify, but seems to me to be one of precision. This is a weird concept, and hard to put into words, but the S1 does exactly what you ask of it, neither colouring nor enhancing the sound beyond what you ask it to do. Curiously, this means that it is equally at home producing the sounds of a vintage American synth as it is the fizzy, squelchy sounds of many Japanese instruments. Let me offer some examples...

Select the pulse wave on Osc1, set its width to about 85 percent, and pass this through the 12dB-per-octave low-pass filter in the MMF section, making sure that the signal level isn't high enough to overdrive the input. Now use pressure sensitivity to control the pitch modulation (vibrato) by patching a cord from CV4 to the LFO Level input, and set the Master CV Modulation Level appropriately. Next, set the filter cutoff to about '4', add a little resonance, create a fairly rapid ASR amplitude envelope, set the VCA response to linear, and add a little Glide. The result? If you've set everything as I have here, you've imitated an early, single-oscillator ARP patch with remarkable accuracy... maybe a simple ARP 2600 patch or, given the pressure sensitivity, a Pro Soloist.

Cwejman have a no-frills approach to design, but that's probably just as well — with a front panel this busy, anything flashier would look horribly over-complex. And the layout is practical, too with the order of the control sections from left to right representing approximate signal flow, and all the patching jacks sensibly out of the way of the rotary controls at the bottom of the unit.Cwejman have a no-frills approach to design, but that's probably just as well — with a front panel this busy, anything flashier would look horribly over-complex. And the layout is practical, too with the order of the control sections from left to right representing approximate signal flow, and all the patching jacks sensibly out of the way of the rotary controls at the bottom of the unit.Photo: Mark Ewing

Alternatively, select sawtooth waves for all three oscillators, tune Osc1 and Osc2 close to unison, and Osc3 to be a major fifth above these. Mix all three at maximum amplitude to overdrive the MMF, which you set to 36dB-per-octave LP mode with a cutoff of '3' and resonance of '7'. Control the cutoff frequency of the MMF using EG1, with an ADSR set to '0', '4.5', '0', and '0', with a modulation amount of about '7'. Now set the VCA Envelope Mix so that only EG2 is controlling the loudness, and set this to '0', '0', '10', and '2' (by the way, the zero Attacks have a 'snap' that you'll obtain from very, very few synthesizers). Again, add a little portamento to taste, and direct CV3 (mod wheel) to the LFO Level, with a suitable Modulation Level in the Master CV Controller. The result? Instant Moog Modular, with Emerson Lake & Palmer's 'Tarkus' and 'Karn Evil 9' pouring forth with seemingly no effort. Add some Overdrive in the VCA section, and the sound gets nasty. I know no soloing keyboard player who would not drool over this; it has a depth and character that most other analogue synthesizers dream about while lying unloved at the other end of the studio.

Finally, let's direct a moderate amplitude of a single, sawtooth oscillator to the MMF in 12dB-per-octave low-pass mode with a cutoff of '3' and a resonance of about '6'. With a filter modulation level of about '8', EG1 then provides a characteristic filter sweep, with ADSR settings of '0', '6', '2' , and '0' while EG2 controls the VCA with settings of '0', '6', '4', and '0'. Simple though this patch is, the result is almost indistinguishable from an MS20's squelchy bass — and I know, because I put it up against my MS20 to check.

Impressive those these sounds are, they are only the start, conjured within minutes of laying hands on the S1. With a little more experience, I was soon conjuring various 'formant' sounds courtesy of the dual band-pass oscillators, and all manner of percussion, much of which — due to the speed of the envelope generators — was more percussive than I can obtain elsewhere. Likewise, the copious ring modulator, FM and sync options meant that atonal and clangorous sounds were a doddle... not just simple to obtain, they had a clarity that I would have struggled to obtain on other integrated or semi-modular synthesizers.

Of course, no review of the S1 could be complete without patching it into a true modular synthesizer, and the next stage was to plumb it into my Analogue Systems RS Integrator. Both synthesizers use 1V-per-octave pitch CVs as well as positive-going triggers and gates, so patching them together was problem-free. Firstly, I used the S1 as a MIDI-CV converter, and various Integrator modules as 'extras'. This immediately demonstrated something that I find with all semi-modular synths; despite its power in other areas, the S1 has insufficient mixers and multiples. When I used the Integrator to provide these, I found that the S1 reached yet another level of flexibility. Then, adding Integrator facilities not found on the S1 — comb filtering, chorus, and so on — the sound expanded still further.

Having tried this, I then inverted things, using the RS Sorceror as the provider of MIDI and CVs, and used the S1 as an expander. Again, everything worked perfectly. As for sequencing the S1 using my Integrator's analogue sequencer... instant Tangerine Dream. Just add electricity.

S1 MkII Brief Specification


  • VCOs: Three, with FM and sync.
  • VCO waveforms: Seven, including three with PWM.
  • PW range: Five to 95 percent.
  • Portamento: 1ms to 10 seconds.
  • Noise generator (with white, red and 'low' outputs).
  • Ring modulator.


  • Range: 0.05 to 50Hz.
  • LFO waveforms: Seven.


  • Multi-mode filters: Two, with variable CV tracking from 0 to 200 percent.
  • Filter topoology: Low and high-pass 12, 24, or 36dB-per-octave filters, plus a six, 12, or 18dB-per-octave band-pass filter.
  • Two filter-input mixers.
  • One freely patchable mixers.


  • Envelope generators: Two, with voltage control of all attributes.
  • Minimum envelope time: 0.5ms.
  • Maximum envelope time: 20s.
  • Output amplifier with overdrive, logarithmic and linear EG responses.


  • Front-panel patch points: 65.
  • Rear-panel patch points: 14.


  • MIDI In, Out & Thru.
  • Patchable MIDI-CV controllers: Four.
  • Rear-panel analogue interfacing: 1V-per-octave pitch CV, Trigger, S-Trig, and Gate.


  • Input: 115/230V, manually selected.

Criticisms? What Criticisms?

Despite the eulogistic tone of this review, there are still places where Cwejman could improve the S1. Obviously, this includes the MIDI implementation (see the earlier box). I have also touched upon the inadequacies of the manual, which could do with a thorough rewrite. Sure, it's explicit, but it's not helpful, and novices will not gain much from it. Then there's the insufficiency of mixers and multiples, although of course there's no panel space to correct this... the S1 is what it is.

Before I close, I want to lay to rest misinformation regarding two 'faults' reported elsewhere. One suggested that, when controlled by MIDI, the S1 generates a loud click when you release a key, even with a slow release time. This is not the case, or at least not on the SOS review model. The other stated that the S1's MIDI input locks up if you move the pitch-bend wheel on a controller keyboard while playing rapidly. I tried to recreate this, but nothing caused even a hiccup in the S1's response.

In fact, I discovered only one real fault with the S1. When you're using the MIDI interface and you press the sustain pedal on the controller keyboard, the existing Gate is curtailed, and the sound passes into its release phase. Later notes are then sustained correctly. Likewise, when you release the pedal, a held note enters its release phase.


I feel that I have still only scratched the surface of the Cwejman's capabilities, and I think that it will be creating new sounds for years to come. As for its sonic character, everybody should be impressed by its clarity, the 'weight' of its bottom end, and the depth of the sounds that you can coax from it. Unfortunately, I can see many S1s living with their mixer inputs cranked permanently to maximum, and their Overdrive knobs cranked even higher. This would be a shame, because it produces beautiful 'clean' sounds, as well as the smooth, creamy timbres usually attributed to the Minimoog and the Voyager which, with its attendant VX351 and CP251 expanders, is perhaps the only current synthesizer to which we can compare it. Nonetheless, the S1 wins this head-to-head for at least three reasons: it's more flexible, it has greater sonic clarity, and it's cheaper. The Moog scores for having a keyboard and for being sexier, but that's still a 3-2 victory for the Swedes.

So, what about the price of the S1? There's no way of avoiding the fact that it's expensive, and it's hard to justify a price tag of over £2000 for a monosynth when a fraction of that outlay will buy you a 'virtual' analogue with umpteen voices and a gazillion memories. But the S1 is a lovely synthesizer, and it falls into that exclusive category of instruments that justify their high prices through quality and flexibility. If you can afford one without worrying too much about the price, you're probably going to want one.


  • It is capable of a fabulous range of excellent sounds.
  • It's extremely flexible.
  • It's very well engineered.
  • It's possibly the best semi-modular monosynth available.


  • Its MIDI interface reprogramming system is arcane.
  • It would benefit from more mixers and multiples.
  • Better documentation is needed.
  • It's not cheap.


There's always been a place for high-quality but expensive top-of-the-line products, be they cars, yachts or synthesizers. That's just as well, because the S1 is a high-quality but expensive top-of-the-line synthesizer, with the sound and facilities to place it at the pinnacle of the analogue pile. If your Granny offers you one for Christmas, do not under any circumstances turn her down.


£2056 including VAT.

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