Review: MOTU Volta

Rather than hitting you with a longwinded history lesson, I’ll do my best to keep this brief: Once upon a time synthesisers didn’t have MIDI ports. That’s right, there was no such thing as a standard protocol like MIDI for synchronising drum machines or layering sounds. Consequently, every electronic instrument manufacturer had its own system for executing these tasks. So say, for example, you wanted to layer sounds from different synthesisers – and let’s face it, you really had to in the days of eight-note polyphony – you’d generally have to stick to the same synth brand. These instruments were typically voltage-controlled devices, with voltage-controlled oscillators, envelopes and filters – the same machines that are generally referred to as ‘analogue’ nowadays.

As you may well be aware, a somewhat cultish following has built up around these instruments, both for their sound, and their hands-on programming immediacy. So much so, that there are now manufacturers building contemporary versions of the good ol’ analogue synthesiser this very day. Like their forefathers, these ‘modern’ instruments don’t have MIDI ports either, so sequencing and sync’ing these devices requires the use of a MIDI-to-CV (Control Voltage) convertor.

So, to cut an about-to-become-long story short, a dual-channel MIDI-to-CV convertor will cost you about 500 bucks. Such a device will drive a couple of synths, chew up additional electricity, and take up physical space in your rack or on your desktop. Mark Of The Unicorn’s Volta plug-in is set to change this, driving as it does a number of CV driven synths – dependent upon the number of spare outputs your audio interface has. It uses no extra studio real estate, sucks up no more electricity than your DAW computer currently uses, and costs a good deal less than the majority of MIDI-to-CV hardware units. Sound too good to be true? Not at all. Volta can drive your analogue machines as effectively, or possibly better than, a hardware convertor. Let’s check out how.

HIGH VOLTAGE

The first thing to consider before purchasing Volta is whether your audio interface can cope with sending voltage signals correctly to your synths. The other slight danger is damaging your audio interface. The prerequisite for correct operation is that your audio interface uses DC-coupled circuitry in its DAC outputs. DC-coupled circuits don’t use capacitors among their components as this style of circuit design can lead to outputs becoming slightly different in timbre as the capacitors degrade over time. As it happens, the majority of MOTU interfaces do use DC-coupled circuitry in their audio output circuitry, the exceptions being the original 2408 and the 896mk3.

Fortunately, I had at hand a MOTU 828Mk2, which handled the job admirably. I took MOTU’s advice (printed in the Volta manual) and soldered up a pair of leads specifically for the task. The manual suggests using TRS (tip, ring, sleeve) jacks at the interface end, and TS (tip, sleeve) jacks at the synthesiser end, with the ring wire ‘floating’ (floating means disconnected, by the way). MOTU has comprehensive instructions about which cables should be used for all its interfaces, but I can’t help thinking it’d be nice if MOTU supplied a couple of cables correctly wired to kick things off, at least so reviewers don’t have to solder up cables! However, MOTU does provide information on how to test your interface to check for DC-coupled circuitry. This information is also on MOTU’s website, along with an audio file to represent Volta’s audio output. So yes, you can test your interface for compatibility before shelling out your hard-earned for Volta.

RETRO REVERSAL

Volta is pretty simple to drive once you’ve got your cabling sorted out. Installing the software side of things is the typical Apple install regime. Copy protection is by virtue of an iLok USB key so is relatively bulletproof and easily transportable. Being a MOTU plug-in, Volta is available as a Digital Performer specific MAS plug-in. It’s also available as a CoreAudio specific Audio Unit plug-in. That’s as far as compatibility extends – there’s no Windows VST version, nor is there an RTAS version for ProTools users. This is odd considering MOTU supplies the majority of its plug-ins in most Windows flavours, including 32- and 64-bit Vista. Windows users do have an alternative in Expert Sleepers’ comprehensive Silent Way, which will pull off similar tricks as Volta. This is also an option for Cubase users on the Mac platform, as Expert Sleepers builds a VST version for OS.

Once you’re up and running, operating Volta is pretty simple to drive. Instancing and opening the plug-in reveals 24 output slots. These slots correlate with the outputs you may have available in your audio system. You’ll need at least two outputs for each monosynth: one for pitch voltage and the other for gate signals. If you need to control four CV/Gate monosynths then you’ll need eight spare outputs. This isn’t a big ask these days as extra outputs are easy to add to most systems, but do be aware of the physical output requirements. Each instance of Volta will address 24 physical outputs, which is, quite frankly, a lot of control sources for a modular synth setup. If you need more, you’ll need another instance of the plug-in and further physical outputs.

Configuration of Volta is largely a drag-and-drop affair: you drag a round ‘Voice’ designated image from the bottom of the plug-in up to one of the slots and you’re ready to go. This process will place two items onto two slots of the 12-slot interface: one for pitch and the other to gate. Clicking on each will then change the bottom area of the plug-in to the relevant parameters for each. The CV or pitch parameters allow you to set up portamento and the length of slide recovery times, legato behaviour, and keyfollow and pitch offset. The envelope, otherwise known as ‘gate parameters’ in the second item, accesses the amplitude envelope behaviour of the gate signal. The envelopes are adjustable to an extremely fine degree; attack for example having 2000 increments available – remember these are voltages we’re dealing with, not MIDI with its paltry 128 steps. If you want to get carried away, and have the modular synth inputs to utilise, you can tie up to three envelope generators into the same group of settings – outputs permitting, of course. There’s also the option to add an LFO at this point.

Beyond these most basic of voltage generation systems are some more esoteric voltage generators. Firstly, there’s a Trigger Sequencer that can be set to between two and 32 steps. Here you also have control over the beat division (speed in other words), swing value, and duration of the note. The Trigger Sequencer can be used in tandem with the Step Sequencer. This can also be used to produce stepped voltages to modulate filters and the like – again, this has control over swing value and speed, along with an octave range menu for spreading the output over 10 octaves. There’s a Clock module that can be added to the mix, again you’ll need another physical output. This can send beat-clock info to devices that accept such voltages (drum machines or the trigger input of a Roland SH101, for example), with the number of pulses per quarter note adjustable from 24 to 1024 – 96 is the usual setting so you can imagine the shenanigans you can get up to with this. A MIDI control generator allows you to assign any MIDI controller to output a control voltage; handy for direct MIDI control over a filter, for example. Then there’s a quite extensive LFO generator that can cycle freely, or sync directly to your DAW’s tempo. The final control option is ‘Ramp’. Ramp is interesting in that it will smooth out DAW automation data into consistent voltage information. DAW automation data is often only output in 128 steps – this fills in the gaps and provides a smooth voltage output.

PRINT & COMMIT

So, as you can see, there’s a vast array of control sources you can spit out to your analogue synth units from Volta. Where Volta becomes an indispensable tool is when consolidating your voltage controlled synth parts. The first tool within Volta for keeping the recalcitrant tuning of your analogue gear in tow is a calibration tool. This correlates the output voltages with the incoming pitch of the synth, and is probably best done at the start of sessions – it all depends how easily your analogue synth’s oscillators drift out of tune. The other nifty aspect of Volta is you can bounce your Volta tracks and lock them in as audio files for even sturdier playback, then edit those files for some innovative analogue sound design.

I must say when I first heard of Volta I thought it to be one of the most ingenious plug-ins I’ve ever seen. Admittedly, I wasn’t aware of Expert Sleepers’ efforts in this area at the time, but having seen both I’m kicking myself for not thinking of it first. As it stands, MOTU’s Volta does exactly as it says on the box – MIDI-to-CV conversion – cheaper and better than before.