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Polivoks Pro

Analogue Synthesizer
Published April 2018
By Gordon Reid

Polivoks Pro

The original Polivoks is rare, iconic, nasty and fabulous in equal measure. So how does a modern-day reincarnation compare with the classic?

The original Polivoks was a remarkable synthesizer, which I covered in some depth in the July 2010 issue of Sound On Sound. Although sometimes dubbed ‘the Russian Minimoog’, there’s little or nothing about its architecture that’s reminiscent of the Moog (that honour belongs to the rarer and, to be polite, less original Estradin 230) because it offers two VCOs with cross-modulation, a dual-mode VCF, two ADSR contour generators with AD looping modes, and a dedicated LFO. And, while it can sound fantastic, its gnarly character is quite different from the creamy smoothness of the Minimoog or, for that matter, almost any other monosynth.

Unfortunately, it has at least two significant deficiencies: despite looking like it could survive an encounter with a medium-sized tank, parts of it are very fragile, and it has the shallowest and possibly the worst keyboard action ever to have had the misfortune to find itself attached to the front of a professional synthesizer. I was therefore rather excited when, a couple of years ago, I heard about a project to recreate the old beast as a desktop module. Called the Polivoks Pro, this promised to be neither a modern interpretation nor a virtual analogue emulation, but a genuine reissue of the original with the same facilities, layout and, of course, sound.

My first reaction when the Polivoks Pro arrived was amazement at how small it is (it’s approximately 17 x 7 x 3 inches and weighs around 3kg) and I wondered how the manufacturers could claim that it’s based upon the original schematics and recreated using original Soviet components. Clearly it can’t be using the back-plane architecture of the Polivoks nor the original board layouts, so I asked Ruslan Neguch, the Project Manager at Polivoks Pro, how it was done. He told me: “When the original Polivoks was designed, the Soviet electronic board tracing technology was quite poor, so the component density could not be high. This caused a lot of problems. We redesigned all of its boards into a single board with a high density of electronics, which also allowed us to improve the oscillators’ stability and make many other improvements. As for the components’ originality, we used the same transistors, filter op-amps, VCAs, and even resistors as before. Some of these were manufactured in the 1980s, some in the 1990s, but they have all the same nominal values and electrical qualities because they were manufactured at the same plants and factories. We have incorporated 85 percent original Soviet NOS (new old stock) components that are no longer being produced, which is one of the reasons why we are only making 100 units.”

But despite this attention to historical accuracy and being described by Neguch as ‘an authentic re-issue’, it was immediately apparent that, from a functional point of view, the Polivoks Pro isn’t a replica; there are knobs, switches, inputs and outputs where none existed before. Neguch continued, “We have tried to preserve the primary functions and parameters of the legendary synthesizer, with all of its charisma. But our recreation of the Polivoks also allowed us to introduce a series of modifications and improvements. Unlike its predecessor, the Polivoks Pro doesn’t drift out of tune, while its new functions expand the creative possibilities available to musicians.”

None of this dampened my enthusiasm to try the Polivoks Pro — quite the opposite, in fact. A stable Polivoks with additional functionality, smooth knobs, clean switches, MIDI and multiple CV control options sounds very attractive to me, whether or not the circuitry has been implemented using 30-year-old components. So the first question to answer is how closely does the Polivoks Pro emulate its inspiration?

The Oscillators

The Polivoks Pro’s dual oscillators appear to duplicate the original synth’s, with each offering five waveforms — triangle, sawtooth, square and two further widths of pulse waves — with footages ranging from 32’ to 2’, LFO pitch modulation (vibrato), cross-modulation of Osc1 by Osc2, and a fine-tuning control on Osc2 with a range of approximately ±14 semitones. As on the original, the generated waveforms are only approximations to their names, which is one of the things that gives the Polivoks its character. Starting with their Osc1 triangle waves, I compared the Polivoks Pro to the original and was surprised by how much brighter the original was, although the triangle generated by its second oscillator was much closer to that of its predecessor. I later discovered that this is intentional; Osc2 on the Polivoks Pro has an asymmetrical waveshape that it closer to the original’s, whereas Osc1 produces something that is tonally closer to the ideal. The sawtooth wave was a much closer match, exhibiting the mildly distorted character that is a characteristic of the original. Likewise, the square wave was a close match, although the reissue sounded ‘hollower’. Given that the Polivoks Pro was calibrated a few weeks ago, while my Polivoks last saw the business end of a screwdriver a few decades back, I can’t say that I was surprised. Likewise, the duty cycles of the other two pulse waves were different from the vintage synth’s, with the consequent differences in tone.

Perhaps the first major functional difference between the two synths is the addition of pulse-width modulation of Osc2. This is controlled by a switch and a knob sited on an extra panel found where the plastic cover concealing the oscillator tuning and scaling trimmers sits on the original; the switch selects the modulation source (either the LFO or the VCA contour) while the knob increases or decreases the amount of the effect. Strangely, PWM not only affects the rectangular waves, but also the triangle wave, skewing this from side to side so that the waveshape oscillates or glides between a sawtooth wave at one extreme and a ramp wave at the other.

The second big difference is the provision of a ring modulator whose inputs are the pulse waves generated by Osc1 and Osc2. In truth, this isn’t a genuine ring modulator, but rather a digital XOR circuit of the type found in the Korg MS20 and some other synths of that era, and which performs the same function as a ring modulator. It generates all manner of timbres that were unavailable on the original synth, which is good, but it does show up a deficiency; the oscillators don’t stay in tune when you switch between waveforms, nor do they track identically. This means that the timbre can shift dramatically as you play up and down the keyboard or if you switch waves, and it made me realise that the Polivoks Pro offers no accessible trimmers to adjust the scaling, which is a problem.

The Polivoks Pro’s front panel measures 43 x 18 cm.The Polivoks Pro’s front panel measures 43 x 18 cm.

The Mixer

Whereas the Polivoks’s mixer offered levels for Osc1, Osc2, Noise and any signal presented to the audio input, the reissue offers Osc1, Osc2, the signal generated by the ring modulator and Noise. Nonetheless, there’s still an external signal input, and this has its gain control next to the PWM controls in the new panel. But with no cable inserted, this knob acts as the gain for the third significant addition — an internal feedback loop. Depending upon the signal being generated by the synth, the result of winding this up can range from gentle thickening of the tone to sonic chaos.

As on the original, the mixer distorts at high signal levels and, as well as imparting grittiness to the cyclic waveforms, it gives the noise a granular character at high amplitudes. The noise spectrum is much redder than that of the original but, while it’s not authentic, that’s not necessarily a bad thing.

The VCF & The VCA

Its dual-mode, resonant 12dB/oct filter was in many ways the defining element of the original Polivoks. It had a harsh character and distorted easily but, while these characteristics may not have seemed desirable at the time, they have found much favour in recent years. Like the original, the Polivoks Pro filter offers low-pass and band-pass modes, both of which will oscillate when asked to do so. As before, there’s no keyboard tracking so, without the use of external CVs, modulation of the cutoff frequency is limited to that provided by the LFO and by the dedicated ADSR contour generator. But, as a bonus, the Polivoks Pro offers a bipolar amount control so that, unlike on the original, you can invert the contour’s effect. The contour also retains a loop mode whose shape is determined by the Attack and Decay Settings provided that the Sustain level is set to, or close to, zero. Experimenting with this demonstrated that the minimum contour times are shorter on the reissue than on the original, which is another bonus.

The VCA section features another dedicated contour generator with the same single-shot ADSR/looped AD architecture as the filter’s, and the gain can again be modulated by the LFO. The special feature here is a switch that defeats the contour and holds the VCA open at its maximum level for drones, effects and processing external signals.

Modulation & Other Facilities

The LFO itself is a simple affair offering seven waveforms including noise and sample & hold, plus a rate control. This embodies more advances over the original synth, which only offered four waveforms. Perhaps more significantly, you can now control the LFO rate using three additional sources. Firstly, you can do so by presenting an external CV to the modulation input. Alternatively, you can flick the left-hand switch on the extra panel to its MIDI position, whereupon the upper note that you play on a connected MIDI keyboard will affect the rate. (The higher the pitch, the faster the LFO.) Finally, you can flick the switch to its Filter Contour position. The rate will then be affected by that contour, with the depth and polarity determined by a knob marked Modulator that sits where the headphones level control sat in the master panel on the original. (In the other three cases, this knob acts as an offset for the LFO rate control.) Interestingly, you can use MIDI control or the VCA contour simultaneously with the external CV input. If there’s a good use for this, I’m sure that someone will find it.

Sharing the master control panel, you’ll find additional knobs for the portamento rate, master tune and master level. But there’s also a switch here...

Round the back there’s a handy translation for those whose Cyrillic is a little dusty... Round the back there’s a handy translation for those whose Cyrillic is a little dusty... Like the ARP Odyssey and one or two other synths of the era the Polivoks was duophonic, but offered a switch to select between monophonic and duophonic operation, the latter of which allowed you to play the oscillators independently; Osc2 was always the lower note with low-note priority, while Osc1 was always the upper, with high-note priority. Furthermore, portamento (if used) was only applied to Osc1, which meant that in duophonic mode you could play synth solos with portamento while any changes in the lower note were instantaneous. The implementation on the Polivoks Pro is slightly different, with portamento applied to both oscillators in monophonic mode, but to Osc1 alone in duophonic mode. (This is different from what is described in the fledgling manual, which describes the same implementation as the original synth.)

In Use

The Polivoks is a very straightforward synthesizer and, to the extent that the Polivoks Pro imitates it, the same is true, not least because the control panel is based closely upon that of the original, and is both nicely designed and a pleasure to navigate. The behaviours of the additional functions are perhaps less obvious, not least because there’s no proper manual as yet. But, printed on its underside, there’s a translation of most of the terms used on the synth, which is useful when it’s not plugged in (although, for obvious reasons, much less so when you have a host of cables hooked up to it). To assist still further, there’s an English overlay provided on the company’s web site. I printed this out as a cheat-sheet and, after a few hours, never needed to refer to it again.

As you would expect from something shiny and new, the Polivoks Pro’s switches are positive and its potentiometers are crackle-free, so when I placed it on top of a high-quality MIDI controller to play it, the experience was very satisfying. I also played it using the CV+Gate outputs of my SH101, and the same remained true. But if the programming and playing experience is rather different from that of the original, the sound is not, and the essential Polivoks-iness has survived. The Polivoks Pro remains superb for aggressive ‘synth’ sounds and, if you direct appropriate CVs to the velocity, aftertouch and modulation inputs, it breathes new life into what was already a powerful lead instrument. As for deep, aggressive and sometimes just plain nasty basses, it’s second to none, and the new ring modulator takes it even further than the original in this regard.

Delving a bit deeper, you can still use the two contour generators in their looping modes to obtain strange, cross-rhythmic effects, and you can still obtain the wicked screams of the original. There are differences, of course. For example, the maximum modulation depths have been increased across the instrument, which is in general a good thing. One interesting consequence of this is that increasing the cross-mod depth increases the pitch of the sound. On the original, the maximum depth was insufficient to make this obvious, so I had never noticed it before. Mind you, using cross-mod on the Polivoks was always an exercise in serendipity, so I think it’s fair to say that it remains much the same on the Polivoks Pro, only more so.

I have long held that a stable Polivoks with improved connectivity could be an excellent addition to many studios and live rigs and, despite being a tad more polite than its inspiration, the Polivoks Pro fits this description well. However, there are two caveats. Firstly, there’s the issue of the inaccurate oscillator scaling and the lack of accessible trimmers to correct it. This needs to be addressed, perhaps by better factory calibration but also by providing end-user instructions on how to do so. Secondly, Russian products have long had a reputation for unreliability, and the designer of the Polivoks, Vladimir Kuzmin, has long since admitted that it could suffer problems as a consequence of poor components and manufacturing errors. I had hoped that the Polivoks Pro would be immune from this, but the review unit had an intermittent fault. Twice during the course of the review, pitch CV1 (which drives both oscillators in monophonic mode and Osc1 in duophonic mode) disappeared. The first time that this happened, I was controlling the Polivoks Pro via MIDI, but when I tested it using the analogue inputs, everything was fine. A while later, CV1 became unresponsive to both MIDI and the pitch CV input. Then, the following day, everything was fine. A week or so later, it became unresponsive again, but then recovered and has been fine ever since. I suspect that this is nothing more than a dodgy cable, a dry solder joint, or perhaps a component on the edge of its tolerance, so I’m not overly concerned... these things happen. Whatever the cause, it should be a simple repair but, had I been an end-user rather than a reviewer, it could have caused no little concern and annoyance.

Final Thoughts

When it was announced, the Polivoks Pro was due to be priced at $2000, with a planned price rise to $2400 after the first few units were sold. However, something then went wrong, and serious disagreements between the technical team and the commercial side of the company ensued. During this period, a number of units were sold at auction, most at the starting price of $1850. Happily, the internal issues now seem to have been resolved, and the company are again talking about developing further products. Following my correspondence with Ruslan Neguch, it appears that the Polivoks Pro is currently available directly from the manufacturer for €1650, which seems fairly reasonable for a hand-built labour of love. Sure, you can buy a second-hand Polivoks for less than half of this, but it will probably have dodgy switches and pots, will lack the six CV+Gate inputs, will lack MIDI and the other enhancements of the Polivoks Pro, will have no warranty, and may require servicing before it can be put to use.

It’s interesting to speculate what the price of the Polivoks Pro could be if the company decided to go into larger-scale manufacturing. If the sound could be retained, many players might be keen. But for the moment, I think that the Polivoks Pro will remain an obscure but very desirable bit of kit, retaining much of the nasty character of its inspiration. Nasty, but fab. I like it.

Alternatives

There have been a handful of suggested improvements for the Polivoks, with schematics for things such as CV+Gate inputs appearing at sporadic intervals. But increasing interest and demand for its sounds has now created a mini-industry of Eurorack products inspired by various sections of the original synth.

Perhaps the most prominent of these are the kits and modules manufactured by Erica Synths in Latvia, which include VCOs, VCFs, VCAs and modulators, as well as a complete 84HP system in which all the modules draw their inspiration from the Polivoks. Alternatives are available from The Harvestman (now renamed Industrial Music Electronics) and other, more obscure sources that you can find on the web.

The Rear Panel

Polivoks Pro rear panel.

The rear panel of the Polivoks Pro has been greatly enhanced when compared with that of the original. In addition to the audio input and output and the MIDI In and Thru sockets with their associated Reset button (which allows the synth to recognise the channel of an incoming MIDI signal), there are now six CV+Gate inputs. These start with the Gate input (which is called Envelope Trigger) followed by two CV inputs for the VCA Gain and the filter cutoff frequency. The latter of these isn’t calibrated for 1V/oct, so you can’t play the filter chromatically, but it’s welcome nonetheless. These are in turn followed by 1V/Oct CV inputs for Osc2 and Osc1. (If monophonic use is selected on the control panel, only CV1 is used.) The last of the control inputs affects the LFO rate. Power is supplied by an external 15V AC PSU using a barrel connector without cable stress relief. Come on manufacturers... at least use a locking plug!

Published April 2018