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.

  • Gavin@FAW

    The most inventive and useful plug-in I have seen in a while. Really forward to hooking up my pro-one to this.

  • poopoo

    The calibrate feature is the killer here.

    I've successfully modified a cheap spdif dac to be DC coupled by shorting out the output capacitors. The output voltage is inverted and offset by +2v so I'll need a little opamp circuit to fix that.

    In the mean time, audio2control in pluggo which does a lot of what volta offers.

  • joshua g

    anyone know if the original rme multiface has dc coupled outputs?

  • poopoo

    There are some test files here…

    If you have a multimeter, hook it up to an output and play the DC test wave file. If you can get a constant voltage on the output it is DC coupled. If your voltage goes down to zero then it is not AC coupled.

  • Varn

    what output voltage is it capable of? bipolar? at least +-5v?
    looks fantastic!

  • CV!

    Wow this is promising.

    It will probably outperform my Encore Expressionist in many ways.

    I'm wondering if there will be a PC vst version available. Not that I've ever seen a MOTU product work correctly on a PC ;(

    I'm wondering what interface are DC-capable, are the Echo interfaces DC, or the cheap Behringer ADA-8000?

    It's a good price for what it does, but if you factor in the price of an audio interface some existing CV converters become competitive, price wise at least. Hardware solutions always have certain advantages as well as the inconviences noted in the article.

    It woule be great if it also syncronised old drum machines with 24/48/96 ppqn.

    I have to say that with the APC controller, Live 8 and this, this year's NAMM news feels like a dream!

  • CV! –

    You can use the clock output module to sync as many different machines as you want. Each clock instance can be set to a different PPQ. In addition to supporting multiple machines, this also serves as a built-in clock divider.

  • bliss

    I want to buy an analog modular just so that I can use Volta!

  • Don't tell this beauty is only for Mac !

  • dead_red_eyes

    Mac only Cyril!

    There's certainly a ton of awesome things for Windows that will never make its way to Mac, so it's nice to have something cool and boutique like this.

    Congrats on the great product Matthew! I'm sure you're going to get a lot of love for this.

  • Great idea. Congratulations!

    Have you considered adding a mode where a modulated AC is sent out instead of DC? Then I think a really simple DIY rectifier box could make Volta usable with any interface.

  • BirdFLU

    This is really the most revolutionary thing to come out of NAMM. I can't wait for it to be released.

  • I'd probably do it the cheapo way by using software I already have (Reaktor) + an existing sound card that I'd mod. I'd like to have an opinion from people who have DC coupled their cards… I assume that a stock card will only have a range above ground (Ie 0-5 V when DC coupled) Anybody have experience? Of course this can easily be fixed with an opamp circuit as poopoo pointed out.

  • CV!

    @ Matthew Davidson
    thanks for your reply, It's great that it does ppq, as this was a feature rarely seen in converters.

    I have a strong feeling it'll be mac only, am I right?

    Also It'd be nice if somebody could explain what interfaces are DC and if workarounds are indeed possible (Nitro2s01?).

    A lot of people had thought of a product that integrated CV control more closely to the modern DAW.
    I use the Expressionist by Encore, which is possibly the best converter around. It has many features and is quite dependable but it's still hard to navigate and lacks control features over MIDI.

    I can't wait to see examples of this product in action!

  • you can do this using the 828mk2 (which is dc-coupled) with only a copy of max or reaktor or whatever tool you have at hand.

    also as nitro said you can turn your soundcard into a dc-coupled one by by-passing the capacitors on the outputs.

    max for live would be an ideal tool to realize tiny midi-to-cv converter-devices.

  • CPRoth

    Just fantastic. I have an Oberheim 2-voice that I modded years ago with direct cv/gate access to all 4 oscillators, filter fc and res, and step trigger input to the 8-step sequencer.

    Big question: My rig currently has 3 828mkIII's on the same FW buss (MAC 8-core 3.0). I had to turn off one bank of ADAT ins just so the FW buss would stop overloading (!). Does anyone know here what kind of hit this puts on a FW buss? I'm assuming I'd have to get another FW card to use this (or go the PCIe route).

  • Hard times for Kenton company…

    This is really bright. What a great year.

  • josh

    holy cow, you answered a dream.thank you!!!!!!

  • rob

    Hz/v ?

  • lekvar

    Man, that's just genius.

  • this looks great, cant wait to get my hands on it and give it a try with some of my gear

  • Andreas

    Is this for real? Seriously? I've been looking for a good Midi-CV for some time now (I need both hz/v and v/oct) but seeing as I already have a Motu 828mkII this plugin wins hands down.

  • Hz/v would be easy to support.
    We can do this.

  • michel

    nice! this could mean that if you wanted to start with a hardware modular system, oscillators, filters, amplifiers and some audio modifiers would do the trick.

    all the control stuff can then be done by volta. perhaps the envelopes would be more convenient in hardware though. but if volta works as advertised, i see no real need to get hardware control modules. (unless you want to do more advanced stuff like modulating lfos with lfos. or could volta do that too?)

    can anybody tell me if this can be done with win xp, max and motu ultralite?

  • nt

    looks lovely, have a couple of questions though ..

    1) will it work with rme ff400 (or 800)?
    2) will it go +/-5V on those interfaces?
    3) i have a filter-cv-mod on my roland sh-1 with expoential tracking. will it be possible to calibrate the signal and compensate so that automation and LFO-shapes make sense? 🙂

    thanks in advance

  • nt

    oh, and another thing, is it possible to combine audio and CV on the same audio interface … as example and 8 out interface where ch1-4 are regular audio and ch5-8 are cv?

  • Korhan

    I have a small A-100 modular system. I have a MOTU Traveler. I have 195 USD. I am happy.

  • glitch

    Now that the idea's out there, just give it a little while. I have a friend who uses plain old volume pedals plugged into the audio I/O of his soundcard as control devices inside his computer. He's written a MAX patch that measures the output resistance and converts that into control data — essentially doing the same thing as the Volta but in reverse.

    I don't know why nobody's thought of this sooner. But I'd give it about a week before somebody starts working on a MAX patch to do most everything the Volta does.

    And while MAX itself isn't free, many (most?) of the patches get given away for free, as well as exported to standalone versions. MAX is cross-platform too.

    In short, Volta is very cool. But if you're cheap, impatient, or on Windows, there possibly a solution on the way too.

  • Royal

    Brilliant invention…

    I would also like to know – is it possible to combine audio and CV on the same audio interface (at the same time) as nt asked….?

  • blz

    damn that is so fraking cool i just wish it was for pc as well. oh well kenton will still get my money i guess.

    congratz on a kick ass plug in

  • David Bulog

    I think this is very significant and profound for the analog synthesizer
    Like the internet was for computers

  • deastman

    This looks fantastic. Unfortunately, I'm PC only. I really hope you find the resources to develop a Windows version as well!

  • nt

    from RME's forum:

    "RME interfaces can't output CV.."

    What a shame …

  • nt

    also, still wonder about this:

    i have a filter-cv-mod on my roland sh-1 with expoential tracking. will it be possible to calibrate the signal and compensate so that automation and LFO-shapes make sense? 🙂

  • da

    The Volta not working with RME is truly a shame… The original post got me all hyped up…

    So any other Interfaces cheaper than the MOTU ones which would do the trick??

  • Magnus Olofsson

    How do you solve the voltage scaling ?
    Modulars like voltages in the 0-10 volt range and audio interfaces only generate max 1.2 volts or so. Or so i'm told anyways.

  • Paul Norheim

    I have a Moog Voyager RME, some moogerfoogers, Logic 8, an Apogee Duet interface and 195 USD.

    Do I have a reason to be happy, or do I need a MOTU interface?

  • Kerls

    use that el cheapo delta sigma codec plus 4580 opamp for DC generation problem solved(?) with crap interface!!! LOL !!! LOL !!! LOL !!!

  • Kerls

    these guys putting Kenton to grave and RME to shame are either ignorant or dumb , well , rather both.

  • Dkon

    Is there a list of what audio interfaces will work with this, aside from the MOTU units? How about any of the Native Instruments ones?

  • Glitch sez:
    >I don’t know why nobody’s thought of this sooner. But I’d give it about a week before somebody starts working on a MAX patch to do most everything the Volta does.

    Well, some of us have been working on this for quite a while now!

    I started experimenting with this back in October, and I can truly, honestly say that if you:
    1) Have a dc-coupled interface (I had an old 828mk1 laying around)
    2) you're able to get midi into Max

    then you can do these things, quite easily.
    this thread was started for this reason:
    – it's especially relevant to all you folks who are getting MaxForLive, of course, because then piping midi through will be even easier.

    Now, if you want the whole shebang out of the box, then the Motu device will be awesome, with the calibration things and such. Neat.

  • Kerls

    mix and match "degree-in-music-technology developer" and "technically challenged userbase", you get MOTU volta. Great stuff.

  • you don't need MAX to get going … i created an ableton setup that controls 3 octaves of my unmodded gakken sx-150 this morning. with pitch LFOs, too.

    just learning that the motu stuff can pass a CV signal from a wav file has saved me the $450 i was about to drop on the moog mp201. (it also saved my ultralite from ebay.)

  • Paul Norheim

    Is there a list of what audio interfaces will work with this, aside from the MOTU units?"

    Could someone provide such a list?

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  • jngpng

    I'm stuck with a Fireface 400, so I was hoping something like the Behringer ADA8000 would work for this. Unfortunately, looking at the reverse engineered schematics of the Behringer it appears that the outputs are high-passed at approx 4Hz.

    Maybe an 828mk1 is in my future, although I'm guessing they've experienced a bit of jump in s/h value with this release.

  • daanbr

    hmmm, measuring my motu mk2 just gives me 4.57 volts. wonder why this is and if volta has a solution for this…

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  • Nate

    that… is… HOT!

    I have a Fireface 800 so I’m assuming I’m one of the lucky ones who may use Volta when it becomes available, whooyay! … well, now I just need to find some old CV synths.

  • brilliant!

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  • FYI, pricing it turns out has not been finalized. We'll update y'all once this is out and there is pricing info.

  • Darren Landrum

    Okay, I have two thoughts on this. The first expands on an idea presented earlier by Randy Jones. The second was hinted at, but something I've been thinking about since this story hit.

    1) Outputting CV signals as AC, which is then rectified externally: I really don't see why this wouldn't be possible at all. The calibration part would probably work differently behind the scenes, but not to the user. Little rectifier circuits would be cheap and easy to make. Something like this might allow for the possibility of using those Behringer 8-in-out units you can buy for almost pennies second-hand. Of course, it might not be so hard to cut and jumper a bunch of output caps on cheap hardware like that, really.

    2) When I first read this story, I started to imagine the possibility of analog synth modules that were nothing but jacks and switches. No expensive pots would be necessary, as everything would be voltage controlled. I'd imagine such synth modules could be made quite cheaply.

    That's about it. Thanks for reading. 🙂

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  • bin

    The stereo headphone socket out from RME's FF 400 , Digiface, Multiface (not II) and HDSP9632 are all DC-coupled, without capacitor at the output jack. so you will have 2 channels of stable DC on these interfaces from the phones.

    Units with a pot (MF II and FF 800) do have one capacitor before the pot, so no stable DC for these interfaces.

  • bin

    you could build a max patch to do this in about 3 minutes… its just turning a midi note number into a signal value with simple arithmetic. the "calibration feature" is a pitch detector that adjusts the output until the sidechain input is tuned.. am i missing something here? why spend 250 dollars?

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  • Graeme

    Does anyone know if there exist MOTU products capable of true _standalone_ operation (not connected to a computer) which would take ADAT in and give analog signal out?

    ..or any other ADAT->analog converters capable of DC output?

    I currently use Windows with a PCI-based audio interface, working well, and I'm not thrilled about getting into firewire or going Mac, so I am thinking maybe I can take advantage of my ADAT outs to expand my system with minimal disruption.

    If viable, the approach might be attractive to people with higher-end ADC/DACs (Apogee etc) who just want to add a little CV out…

  • TheDude

    Wait if this is voltage not midi, that mean it can control guitars and stuff two?

  • @TheDude: it can't "control guitars", but it can control anything with an appropriate Control Voltage input, which does include some guitar effects (like the moogerfoogers).

  • I hope they add the following! Different temperment scales, Auto keyboard calibration of Karpus-Strong type Delay module, Velocity & keyboard scaling of each ADSR stage. Add the ability to mix multiple voltage types per instance (Key follow pitch + Mod Wheel controlled LFO at output 3). Volta VCO output for FM (amplitude of Volta VCO modulated by Volta Envelope).

  • anyone know of a list of compatible interfaces? presonus firepod for instance…

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  • Somasen

    I'd like to add to the chorus of voices who want to know output voltage range.

    Granted if you have a modular you can probably scale voltage as needed, but what are we working with here? This is important info. What kind of min/max DC voltage level can a MOTU analog output sustain?

  • bin

    someone here… says 4.57v for a MOTU mk2 fw

  • xpez2000

    synthesis technology is loving this

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  • I love this app! I use a Serge Analog Modular, and unfortunately the Trig sequencer in Volta with Ultralight mkii does not deliver enough voltage to actually trigger boolean logic, or any other triggerable Serge modules except comparators. The Note sequencer however CAN be used to trigger at least some of these things. I'll probably post a youtube evaluation after I figure all this out.

  • I was wrong! The Trig sequencer sure can send effective pulses through the Ultralight mkii!

  • ebull

    I am looking into getting Volta but wondering if any readers out there can shed some light on an issue I have. I have a Doepfer modular system with some Cwejman oscillators. They rely on the Doepfer system bus for a gate signal they dont have an external gate input jack. Just wondering how would I get a gate signal from Volta to trigger them?
    Would I have to use a Doepfer Midi/CV A-190 for the gate and Volta just for CV pitch etc
    Hope this question makes sense

  • Do you know of any freeware/cheaper applications that do the same or similar?

    Motu Volta does not seem to support 0 to +8v scale like on MS-10/20/50