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Korg Volca Modular

Semi-modular Synthesizer
By Rory Dow

Korg Volca Modular

Korg bring West Coast modular synthesis to the masses with their most ambitious Volca yet.

The Korg Modular will be the Japanese giant's eighth addition to the Volca series. Each one focuses on a particular task. So far we've had bass, keys, analogue drums, samples, FM, kick drums and mixing. The latest adds something you might not have seen coming: West Coast modular synthesis.

Coast Vs Coast

Bob Moog and Don Buchla were both developing synthesizer technologies in the 1960s on different sides of the USA. Moog started his work in New York, whilst Buchla was over in California. They both had distinct styles and their geographical polarity gave them the monikers, East and West Coast. Moog's style centred around subtractive methods involving the now ubiquitous oscillator, filter and VCA topology. Buchla's techniques employed wave folding and frequency modulation to control harmonics, and used low-pass gates and function generators instead of filters, envelopes and LFOs.

The huge popularity of Moog-style East Coast synthesis means we all know how an 'analogue synth' sounds and functions. West Coast techniques on the other hand have remained relatively underground and exist almost exclusively in the modular domain. High prices and the less pragmatic, more experimental nature of Buchla synths made them less common. Korg must be commended therefore for choosing the less obvious route for the new Volca Modular.

I'm sure we're all familiar with the Volca format by now. The plastic case, built-in speaker, battery compartment for six AA batteries, touch-sensitive keyboard and on-board sequencer are all present. Connections along the top include a 9V DC power input (as with other Volcas, the adaptor is not included) as well as mini jacks for Sync in and out, a CV input and the main audio output.

Being a modular, there is of course a need for many more inputs and outputs — 24 inputs and 26 outputs to be precise. The size of the Volca means that Eurorack mini jacks are out of the question, and so Korg have opted to use small pin connectors. A generous bag of mini patch cables is included. Each cable has a sharp pin on each end which slots neatly into the sockets spread around the front panel. This works well enough, although I found it all too easy to bend the pins when moving pots or making additional connections in an already crowded pin matrix. Inputs and outputs, both audio and CV, are helpfully marked on the front panel and every connection has either a symbol or a guideline showing you which control it's connected to. If you have failing eyesight, or like to work in dark studios, you may find yourself squinting a lot.

As with many of the previous Volcas, any control which can be modulated is given a clear plastic control through which a red LED shines in order to show you the current value, useful when you patched something days ago only to return to it wondering what on earth is modulating what.

How Many Modules Can You Fit In A Volca?

Korg have packed a lot in: a dual oscillator, capable of wave folding and frequency modulation, two function generators, two low-pass gates, a utility module, a 'Woggle', a splitter, a sequencer and a digital effect simply known as 'Space Out'. Many of the modules are internally connected, allowing the synth to be used without pin cables.

The dual triangle oscillators are arranged for frequency modulation; one is the carrier and the other the modulator. The Ratio control affects the relative pitch between the two and Mod changes the amount of frequency modulation. The result is passed through a wave folder, which is controlled with the Fold knob. All three controls have CV inputs, in addition to another for the main pitch control. Both oscillators are available on separate audio outputs. This oscillator setup, simply named 'Source', is one of the main features of a typical West Coast synthesizer. Without a filter or even any additional waveforms, there's a huge range of harmonic possibilities.

Low-pass gates (LPGs for short) combine the functions of a voltage controlled amplifier and a low-pass filter. The signal level at the input dictates both the amplitude and the frequency content of the signal at the output. Both low-pass gates are identical. The first is internally connected to the output of the Source section, but this can be overridden using the patching points. Each low-pass gate has inputs for audio, CV and a signal output.

The final piece in the audio signal path is the Space Out effect. It's described in the manual as a "digital spatial effect". It sounds to my ears like something between a spring reverb, a BBD delay and big old plate reverb. Any signal put through it instantly sounds like something from the Forbidden Planet soundtrack. It doesn't come with any control other than wet/dry, which can be controlled by CV if you wish. It won't always be what you're looking for, but it's a nice thing to have and some cool feedback tricks can be achieved by patching its output to an input further upstream.

West Coast Modulation

The two function generators look very similar on the surface, but they operate slightly differently. The first is an AHD generator. It creates a control voltage with three phases: attack, hold and release. There is a gate input and CV inputs to control the attack and release stages, which are also adjustable via the front panel controls. The outputs provide both a positive and negative version of the envelope and a third output sends a trigger when the release phase has ended.

The second is a rise-fall generator. It goes up and it comes down. The Shape control balances the ratio between rise and fall times whereas the Time control changes the combined time it takes for both the rise and fall to occur. Both controls have a corresponding CV input. Unlike the AHD generator, the rise-fall generator doesn't need a gate input because it doesn't have a hold section, but a trigger input is supplied instead. At the output there is again a positive and negative CV and a trigger output at the end of the cycle.

The two function generators could be thought of as an envelope and an LFO. But that would be missing some of the flexibility. With the rise-fall generator, patching the end-of-cycle trigger to its own trigger input will create a looping rise-fall cycle which is essentially a triangle LFO. But there are other ways to combine the functions. For example, you can create longer, complex envelope shapes by using the end-of-cycle triggers from one function generator to trigger the next.

Other modulation sources include the Woggle — an important part of every Boy Scout's uniform! In this case however, it is a rather silly name for a Sample & Hold circuit. Without any cables connected, it samples an internal pink‑noise generator every time a note occurs, but pin inputs for the sample and trigger can be used to Sample & Hold anything you like. The Woggle offers two outputs, one stepped and one smooth. The smooth output is identical to the stepped, but glides between each value at a fixed rate.

Of course, modulation is no fun unless there is some way to scale it. Have no fear, the Utility module is here. There are three inputs, labelled A, B and C, and two outputs which mathematically combine and attenuate the signals in different ways. C is used to attenuate B using either its input or the corresponding knob. The result is then added or subtracted from A, depending on which output you use. The inputs will accept audio signal as well as CV signals. The Utility module is a jack-of-all-trades: manual attenuator, VCA, mixer, ring modulator, DC offset and I suspect many more that I haven't figured out yet. It is potentially the trickiest module to master but to help you on your way Korg have included some excellent patching examples in the owner's manual. And I'm sure online communities will be sharing further knowledge and patches soon enough.

The last piece of the modulation puzzle is a handy Split module, known in many modular circles as a multiplier. It can be used to either duplicate an input to two different outputs or in reverse to mix two inputs to one output. The Split module will cope happily with either audio or CV signals.The Volca Modular shares the same physical format as its siblings, but lacks the MIDI input found on other models.The Volca Modular shares the same physical format as its siblings, but lacks the MIDI input found on other models.

Sequence Me

The sequencer section will be familiar to anyone who owns a Volca already. Record, Play, Memory and Function buttons work in tandem with the 16 keys on the touch strip to allow both live and step recording, as well as pattern selection and a host of other functions. There are 16 pattern memories and each one can be 16 steps long. A pattern is selected by pressing the Memory button and selecting one of the 16 keys. They can also be chained by selecting a start and end pattern, which will cycle around the patterns in the range in numeric order.

Each sequencer pattern can make use of Active Steps, which allows for turning individual steps on and off. Motion Recording is also present, allowing knob movements to be recorded into the pattern. One of the fun things about the Volca series is that each one approaches sequencing slightly differently. The Volca Modular is no exception and brings some interesting new features to the table. First up is Bounce mode. It causes the sequencer to play forwards and then backwards, bouncing endlessly between the two. To add further interest to your patterns there is also a Stochastic mode. When enabled, the sequencer will randomly choose the next step from four choices: forward, skip one forward, backwards or repeat. This causes an unpredictability in the next step whilst still retaining some forward movement. Bounce and Stochastic modes cannot be enabled at the same time but they are nonetheless useful for adding some non-linearity to basic patterns.

The sequencer is internally wired to the Source oscillator's pitch and the first of the two low-pass gates. This allows it to function without any patch cables connected. A small row of six sockets gives you modular connectivity in and out of the sequencer. The single input lets you control sequencer speed, although I was a little disappointed to find it only adjusted the speed by ±20 bpm, not the full range of 56 to 240 bpm. Outputs are provided for gate, half‑speed gates, third‑speed gates, quarter‑speed gates and pitch. Using these clock divisions to trigger various modules can bring all manner of additional rhythmical complexity to your sequences.

Micro Modular Microtune

Not content with the Bounce and Stochastic additions, Korg have also included scale quantising and microtuning. Fourteen different scales are available including major, minor, pentatonic, Exotic, Japanese and even a Chromatic Reverse mode, which inverts the pitch tracking of the keyboard. Selecting a new scale will remap the keys to only include notes from that scale. Changing the tonic will transpose the keyboard so that the tonic of the scale is always in the same place regardless of what key you're in. Changes made to the tonic and scale will affect the recorded pattern and will also be saved with the pattern. This makes experimenting with melodic variations of the same pattern a breeze and it's very easy to come up with interesting melodic progressions and key changes using different patterns.

Microtuning seems to be a feature that Korg are championing of late. It's not uncommon to find microtuning features in more expensive synthesizers, but its inclusion in Korg's budget Monologue synth (lobbied for by none other than Richard D James) has been met with much approval. And here it is again. You can fine‑tune each note of the currently selected scale by holding the note and using the Microtune knob to adjust by ±100 cents. A handy Clear function is available to reset all the adjustments. As microtuning implementations go, it's a fairly basic one. There are no microtuning presets and no way to import or export microtonal scales. So if you have hopes of tuning the Volca Modular to match some other equipment or your favourite scale, you're in for a potentially long and manual process, done by ear. Having said that, tuning adjustments are saved with the current pattern so, if you do tune up a killer scale, at least you can recall it later on. Sadly the microtuning will only work with the on-board sequencer. If you decide to sequence from an external source, then the microtuning and scale/tonic settings will have no effect.

In the spirit of adventure, Korg have also included some randomisation functions. You can randomise the current pattern notes, the active steps and the microtuning. There's no undo here, so be sure before hitting the button. The remaining functions available via the Func button are utilitarian. Octave up and down for the keyboard, clear active steps and clear all.

Conclusion

The Volca Modular sounds wonderful. It is capable of a huge sonic palette and it positively encourages experimentation. Of course, without inserting any patch cables, the basic configuration will only produce basic results. Judging it without inserting a patch cable would be doing the Volca Modular a disservice. Once you get busy making connections, you will be rewarded with a vast range of interesting and unusual sounds. In just a few days, I stumbled through beautifully soft basses, alien drone textures, radiophonic bleeps and bloops, kick drums from hell, electro percussion sequences, nostalgic warbly leads and more. Close your eyes and you could be listening to a modular system 10 times the size and 20 times the price.

We do have to talk about the size; the (miniature) elephant in the room. The Volca Modular does feel cramped. The biggest problem is getting to the controls when there are lots of patch cables plugged in. Some of the inputs and outputs are very close to the knobs and often on more than one side. Getting clear access with all but the slenderest of fingers can be troublesome — pins can get bent. I can't help feeling that putting all the modular connectors at the top of the unit would have eliminated this problem, leaving the knobs free for unfettered twiddling.

Ultimately, however, the size doesn't matter because I found myself having fun and making great sounds. If you love analogue synthesis, but crave something a little different, then the West Coast approach will deliver. I suspect the Volca Modular will be many people's first taste of West Coast synthesis, and possibly modular synthesis full stop. There isn't anything else at this price that can give such a genuine taste of those two worlds and that's fantastic, although if you get bitten by the modular bug your bank manager might disagree. The fact that Korg have even attempted to fit a modular environment into the Volca still astonishes me. What's even more astounding is that they've pulled it off.

Click and check out the SOS Tutorial video course on the Volca Modular.

Alternatives

A couple of similar synths come to mind. The first is the Bastl Instruments Kastle, (reviewed in July 2017 by Paul Nagle). It's even smaller and cheaper than a Volca, at €84. It uses the same patch‑cable pin system, and whilst it's not exactly West Coast synthesis, it comes close by using phase distortion and waveshaping. It has far fewer modules and features than the Volca and is completely digital, but it's open source and hackable if that's your thing.

The Make Noise 0-Coast (reviewed again by Paul in October 2016) does offer West Coast synthesis in a desktop format, but at a higher price ($499). It isn't exclusively West Coast, hence the name, but elements such as the low-pass gates and function generators are certainly there. The 0-Coast boasts MIDI connectivity, full Eurorack compatibility, a solid metal case and dual arpeggios, but misses out on the Volca's sequencer, reverb effect and battery operation.

The Outside World

The Volca works on a voltage system of -3.3V to +3.3V, making it incompatible with Eurorack, which uses higher voltage ranges. So even if you could get special cables made up, you're unlikely to be patching your favourite big-format modular directly into the signal chain. Korg haven't left you completely isolated, though. There is a single Eurorack CV input jack which converts to two pin‑style outputs. The mini jack allows you connect two CV inputs by using a stereo‑to‑mono splitter cable (not included). The left channel takes the incoming Eurorack CV (clipped at ±5V) and converts it to ±3.3V. The right channel expects a 1V/oct signal and converts it to the Volca's internal pitch voltages. If a mono cable is used instead of a splitter cable, the same signal will be passed to both pin outputs.

This is great news for any one who wants to sequence the Volca externally. You simply use the two inputs for CV and gate. Sadly there's no equivalent Eurorack‑compatible CV output, so you're not going to be using the Volca's sequencer in the outside world. If you were hoping for MIDI connectivity, then you're out of luck.

Pros

  • A West Coast modular in a Volca. Wow!
  • It sounds fantastic.
  • The Volca sequencer: now with scale quantising and microtuning.
  • Battery operation.

Cons

  • Patching is inevitably fiddly.
  • Limited modular connectivity with the outside world.
  • No MIDI.

Summary

Korg have attempted something brave — a modular synth in a Volca package. It maintains all the sonic possibilities of modular without the size or the overdraft fees. All hail the Volca Modular!

information

Price is yet to be confirmed at the time of going to press, but expected to be comparable with other Volcas.

www.korg.com

Price is TBC at the time of going to press, but expected to be comparable with other Volcas.

www.korg.com

Published February 2019