Computers speak digital signal. Analog synths and modulars speak control voltage. (It’s sort of a “men are from Mars, women find these metaphors insulting” kind of situation.)

What if you could bridge the two elegantly and graphically, using a drag-and-drop, modular interface with calibration and control features? MOTU has developed a solution called Volta. It’s a plug-in that turns your audio interface into a control voltage device. It works with all MOTU audio interfaces that have quarter-inch outputs, and MOTU intends to make it work with any 3rd-party audio interface with DC-coupled quarter-inch outs.

In other words, one software plug-in does more than what a similar module would do, more easily, more elegantly, all from your Mac. It makes your computer a powerful tool for analog synths in a way that it hasn’t been before – arguably in a way that even digital synths can’t approximate.

I’m pleased to welcome Matthew Davidson of MOTU in a CDM exclusive on Volta’s launch. He describes in detail what Volta is about, and why MOTU developed it.

All photos courtesy MOTU.

A video demo follows, as well.


What is Volta?

Volta is software; a virtual instrument that turns your audio interface into a voltage control interface. Anything with a control voltage (CV) input can be automated from your DAW with Volta. This includes modulars, analog mono synths and even effects processors like the moogerfoogers.

Volta provides access to the automation system of your DAW through ramps. You can draw in whatever whacky timeline based automation you desire and use this high resolution data to control anything with a CV input. No stair-stepping or zipper noise. You can also route any MIDI controller to control voltages. Volta provides audio-rate rendered software LFOs, step and trigger sequencers.

Each instance of volta supports up to 24 slots of outputs, and you can have as many instances of Volta as your hardware allows. For example, a MOTU PCI-424 system with four 24io interfaces provides 96 channels of output.

Of course, you can also use Volta to send note information. MIDI information goes in, and control voltages go out. All control signals are running at audio rate, and MIDI note playback is pre-buffered. This provides sample accurate timing of your external hardware.

Volta First Look from Matthew Davidson on Vimeo.

(Click through to Vimeo for HD video)

How did Volta come about?

The limitations of hardware CV-MIDI converters are pretty frustrating. Their workflow…these things are programmed though tiny LCD windows and they’re designed to be a ‘set up once and forget’ type of affair. So, you spend an evening with the manual in your lap (an abridged version, translated from German) and create what you think will be a good ‘general purpose’ patch. So, as long as you stick to that and nothing else, you’re set. Only… that never turns out to be the case. You want to reassign controllers. You want to turn an envelope into a trigger. You want to move outputs around. Total nightmare.

But usability is only one issue. There are annoying technical limitations to hardware MIDI to CV convertors. Resolution. Why should we be limited to 8-bit controllers? Why can’t we leverage the awesome automation system in our DAW? Latency/lag; it is critical to have events occur at the points you specify in your sequence. If an onset occurs before a massive controller jump, the results are disastrous.

We had a hunch that a software solution could solve all these issues, so we hatched a plan than became Volta…

Tell me about the calibration feature.

The calibration feature came about as a direct result of ensuring Volta would work on non-MOTU interfaces. In our research, we found output levels varied not only from model to model, but interface to interface and even output to output. We were nearly ready to give up by this point until we came up with the idea of a closed-loop calibration system. Most oscillators have multiple outputs, so why not plug one back into the interface and measure the frequencies coming out of it? Then you can create a complete profile that addresses any non-linearities in both the interface and the oscillator. You can even tune self-oscillating filters this way.

I’m curious if some non-tracking oscillators like the livewire Dalek modulator and the Blacet dark star chaos will track with Volta. We will test that out. You can walk away from your modular and come back hours later, hit ‘calibrate’ and you’re back in tune. It is like the tune button on a Prophet 5. Volta not only tunes and scales your oscillators, but when you hit a C4, you get a C4.

Some of my personal impressions of using Volta

It feels like a combination of some of the programming conveniences from MX4, like using multiple host-synced LFOs to create rhythmic effects, combined with everything I like about analog. As I write this, I’m modulating a filter with one Volta LFO, and modulating the waveform morph feature on a Plan B Model 15 VCO with another synced LFO to create a percolating effect. This really wasn’t easy or possible before.

Things I didn’t expect

The chicklets display at a glance what is assigned to what outputs. A hardware MIDI to CV convertor is a black box with no visual indication of what is coming out where. If you’re used to tracing cables with your eyes and fingers, this was an unexpected workflow bonus.

I can’t emphasize enough what a revelation it is to have everything in sync with your project. Syncing an LFO in the analog realm to your DAW usually involves sending a sync trigger to reset the onset of the LFO, then you have to manually tweak the period of the LFO to line up with the sync point. With Volta, you just drag on an LFO, set the metric period and you’re done.

The audio output of your modular gets returned back into the Volta instrument plug-in so you can easily apply host-based effects to the output. This naturally leads to a whole world of host-synced effects processing with delays, things like Automaton, etc. You can put real time MIDI effects on the MIDI input, like an arpeggiator.

So, in a nutshell, complete, accurate, precise digital control of your modular from your DAW via a virtual instrument interface. I would be curious to hear your reaction to what I’m describing.

How much is Volta?

Pricing has not yet been announced.

Do I need a MOTU audio interface?

Volta will work with any audio interface with DC-coupled outputs. All MOTU interfaces (PCI, Firewire and USB) with 1/4″ outputs will work.

Do I need Digital Performer?

No. Volta is an AU plug-in, so it will work in Logic, Live, Garage Band, Digital Performer – anything that supports AU instruments. Some features like sample-accurate timing require a sample-accurate host.

Will Volta work with 1.2v/oct gear?

Volta’s calibration feature supports different oscillator scaling standards.

Where can I buy Volta?

Visit for further info. You can sign up for an email alert when Volta is available.