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Native Instruments Komplete Audio 6 MkII

USB Audio Interface By Robin Vincent
Published September 2019

Native Instruments Komplete Audio 6 MkII

If you want an affordable audio interface that also offers control of your modular system, read on...

Into the crowded market of portable USB audio interfaces, Native Instruments have released three new boxes. The first two, the Komplete Audio 1 and Komplete Audio 2 are sub-£100$150 two in/two out jobbies that if it wasn't for their striking looks would be lost amongst the crowd of similar offerings from many other companies. But following on a couple of months behind is the Komplete Audio 6 MkII. This has a solid feature set at a decent price, but there's something a bit extra that may well tempt you away from the competitors.

This is the successor to the long-lived Komplete Audio 6, originally released in 2011. It was a smart little box made from an aluminium extrusion and featured the six channels of audio (four analogue inputs and outputs, and S/PDIF) that gave it its name. At a time when everybody else was making fiddly little 1U rack height devices with all the controls on the front panel, it had a very cool volume dial on the top. The MkII goes for a completely different aesthetic but retains all the most important features.

The Komplete Package

All three of the interfaces follow the current Native Instruments design philosophy of smooth lines, square corners and deeply black, minimally featured surfaces. The hard plastic of the KA1 and 2 is outclassed by the metal sandwiching of the KA6 MkII. But they all share the very reflective and shiny fingerprint-magnet monitoring LED panel on the top. The KA6 MkII is weighty with effective rubberised feet that stop it slipping on the desktop. It is also larger than the original, being roughly the size of a Game Of Thrones DVD boxset and just as imposing. It keeps the ergonomically useful top–mounted volume knob from the original, but this only handles the output volume of channels 1+2.

All other controls are on the front, and they are exactly as you'd imagine them to be. Two 'combi' mic/line/instrument inputs have individual gain knobs and 48V phantom power. (There's a mono/stereo switch for linking the channels.) Twin headphone sockets with independent volume control, for you and a friend, can be switched to monitor either outputs 1+2 or 3+4, and a knob mixes between direct input monitoring and software monitoring from the host.

Round the back of the Komplete Audio 6 we find a USB port, MIDI I/O sockets, S/PDIF I/O, and four audio outputs and two audio inputs on quarter-inch jack sockets.Round the back of the Komplete Audio 6 we find a USB port, MIDI I/O sockets, S/PDIF I/O, and four audio outputs and two audio inputs on quarter-inch jack sockets.

On the back there are the other two inputs, four analogue outputs and S/PDIF coaxial in and out. There's also the very welcome sight of MIDI in and out ports, which is often a rarity at this price. A single USB socket rounds off the connections and points out that this is purely USB bus powered. There's no socket or option for a power supply.

At the price of £189$249 the Komplete Audio 6 MkII is a decent, robust, elegant and well-built audio interface with a common physical feature set. The knobs are small but good, with very little play or noisiness. The switches switch like they should and the sockets plug in solidly. It could be a bit humdrum if it wasn't for the fact that it looked so fabulous!

Once you've installed the drivers (Windows) and plugged it in, the monitoring panel lights up pleasingly. The white text stands out nicely from the reflective black. Three white LEDs tell you if it's getting USB power, if the phantom power is on and whether there's any MIDI activity. There's separate input monitoring on all four analogue inputs, with four blue LEDs leading to a red LED peak light. Only outputs 1+2 get LED monitoring. It's all quite sparkly on that reflective surface and it is so much more helpful to have it on the top of the interface rather than squeezed onto the front panel like so many others do. In fact there are no indicator LEDs on the front panel at all.

On the computer there's very little in terms of control software. There are no mixer applications or routing options, just a box to set buffer size and sample rate. And that's fine by me. I often find that audio interface mixing applications tend to get in the way, adding an extra level of potentially getting things wrong between the hardware and your DAW. But it can also be a little too simple as you can't set up any monitoring options or routing. So you can only 'direct monitor' via the headphone sockets on the front using the knob to mix between direct and host. You can't direct this to an output on the back and get a mix of wet and dry input through your main speakers. Once you're in your DAW or virtual instrument then all six inputs and outputs present themselves for work via the ASIO driver and you're ready to go.


Time to put it through its paces. The original KA6 has always performed well — Native Instruments managed to write great drivers that didn't bother the CPU until you got down to very low buffer sizes — so I was keen to see if the new one was up to that sort of level. And yes, it's remarkably good.

Recordings were crisp and clean with a good amount of headroom, with nothing unusual or remarkable for this price. In terms of latency, from the buffer size menu, you can select all the way down to an almost mythical eight samples. Most interfaces rarely give you an option below 32 samples. This translates to a millisecond or two of latency, but it's not quite as simple as that. The control panel has a 'Safe Mode' tickbox that hides a secret buffer in the background, allowing the input latency to come down to tiny levels while keeping the output latency at a slightly buffered level of an extra millisecond or two to prevent audio glitching. It's a useful function if a little bit mysterious.

The new Komplete Audio USB audio interfaces are joyously simple, lovely to look at, well designed, robust and portable.

So, when testing with the Oblique RTL (Round Trip Latency) utility with Safe Mode engaged, the best round trip latency (that's in and out again, like when monitoring through effects) it could achieve with eight samples was 5.5ms. Without Safe Mode it got down to 4.3ms. At 64 samples it managed 5.6ms without Safe Mode and 6.6ms with it on. At a more typical setting of 128 samples round trip latency was 11.1ms with Safe Mode and 9.2 without. Around 10ms round-trip is pretty standard for this level of USB audio interface and so the fact that it can cut that in half is pretty impressive. In doing some testing on the output latency while running virtual instruments I found I could get down to just a couple of milliseconds and still have a completely glitch free real-time audio response.

Is Safe Mode important? Yes and no; it really depends on your system and what you're doing. On my test machine — a Surface Pro 6 i5 running Windows 10 — it would crackle when playing a complex polysynth virtual instrument at eight samples, but after turning on Safe Mode the glitches went away — and the feel and response of the instrument when playing was identical, or at least the difference was too small to notice. Instead of all this Safe Mode business the options could be more comprehensive, but I guess it's just trying to keep things simple and glitch free in the most possible cases. In terms of CPU performance I found that the processor only started to get bothered by the strain at 32 samples, and if I was prepared to sacrifice a couple of milliseconds at 64 or 128 samples then the CPU would hardly blink.

DC Coupling

So far, so good, but what sets the KA6 MkII apart from any other audio interface anywhere near this price is that the four analogue outputs are DC coupled. They do not have the filter that's found on most audio interfaces that removes the very low frequencies and flat voltage interference. This means that the KA6 MkII can pass control voltages (CV) from software to hardware modular or semi-modular synthesizers and devices. You can have four channels of CV for controlling your Eurorack — that's amazing! Well, amazing in that it's hard to find audio interfaces that do this at this price. The PreSonus Studio 68c is one slightly more expensive possibility, but you'd normally be looking at a MOTU interface or something similarly high-end for DC-coupled outputs. Or if you wanted it all in your Eurorack then the Expert Sleepers ES-8 would do the job, but has no mic preamps or instrument inputs.

So how well does it work? Pretty good... To make use of the DC-coupled outputs you need to be running software that outputs control voltage. Reaktor can do it within the Blocks framework and treats CV just like any other audio signal. Bitwig Studio has a number of CV–related devices in which you can select a physical output for the modulations you are creating. Ableton Live 10.1 has the new CV Tools devices for exactly this sort of thing and there's also VCV Rack, Audulus, Voltage Modular and others. All they need is a physical DC-coupled output to be able to send CV out to your external gear. So, for instance, with Ableton Live's CV Tools you can send out LFOs, trigger sequences, or pitch and gate information. You can sequence and modulate your rack directly from your DAW via the Komplete Audio 6 MkII. It's brilliant.

You only have the four DC-coupled outputs, and if you're also using audio from your computer then you've only really got outputs 3+4 spare for controlling your rack. It's vital that you don't get your outputs confused as your speakers are not going to thank you for sending them flat voltages.

But it's not all plain sailing. Since the KA6 MkII is bus powered it can only manage to generate ±2V, giving you a voltage range of 4V. Eurorack normally deals in ±5V. So when routing an LFO from CV Tools to your filter module the sweep may feel a little limp. Similarly, when calibrating the CV Instrument it's going to offer up a maximum range of four octaves, which is probably plenty in most instances but not as wide as it could be. It doesn't have to be a problem; I am more often than not attenuating LFOs in my rack to create a smaller range of modulation, so ±2V is fine. However, you can also add more range to the signal with some CV shenanigans from a module you probably already have. You could use channels 2 or 3 on the Make Noise Maths to add some voltage to the range. Daisy–chaining both will get you up to about ±5V. Or for less than 40 quidaround $50/$60 you could pick up a Doepfer A-183-3 DC Amp, which could do the job without any bother.

The Komplete Audio 6 MkII's front panel is where we find the XLR/jack inputs and associated gain controls, a knob that mixes direct input monitoring and software monitoring, and a pair of headphone ports with volume controls.The Komplete Audio 6 MkII's front panel is where we find the XLR/jack inputs and associated gain controls, a knob that mixes direct input monitoring and software monitoring, and a pair of headphone ports with volume controls.

There's one other issue with the DC–coupled outputs and that's to do with the nature of outputs 3+4. They are balanced and only balanced. Outputs 1 and 2 can handle balanced and unbalanced cables, and so work perfectly with a regular Eurorack patch cable with a 3.5mm to 6.5mm mono adaptor on the end. Plug the same cable into output 3 or 4 and you only get half the waveform. Only the positive CV is getting through. I tried a number of different cables and adaptor combinations to try to remedy the problem and found that the easiest solution was to use the same cable as before but to pull it out half a centimetre so that the tip connected to both signal paths. The result was that I got my full ±2V back, but it was polarity inverted — good enough at a pinch!

In researching this issue I found that it's actually a problem on most audio interfaces that say they are DC coupled. I discovered a few forum threads of people trying to work with MOTU and PreSonus interfaces and facing a lot of frustration in trying to get CV out of the DC–coupled outputs. The answer came from Expert Sleepers, the people behind a suite of CV plug-ins called Silent Way and the ES-8 DC–coupled USB audio interface for Eurorack. Their hardware has none of these problems but a lot of people are running into trouble with other interfaces when using the Silent Way plug-ins. As I've discovered on the KA6 MkII, it all comes down to getting the correct cable. One solution is to use a 'Y' audio insert cable, which has a TRS plug on one end and two TS plugs on the other. This gives you a dual CV output where one of them is inverted, which might have its own uses. Alternatively, Expert Sleepers can sell you a 'floating ring' cable that has a quarter-inch TRS jack on one end and a mono mini-jack Eurorack patch plug on the other.

Although the DC coupling is not exactly flawless, once you've got over the hurdles it is genuinely workable and opens up whole new areas of software/hardware communication and creativity.


The new Komplete Audio USB audio interfaces are joyously simple, lovely to look at, well designed, robust and portable. The driver architecture and performance is remarkable at this price. Do the additional features of the Komplete Audio 6 MkII make it worth around twice the price of the KA1 or KA2? Yes, I think so. The second headphone output is helpful and the MIDI interface can be a complete godsend, as little hardware synths seem to keep appearing on my desk. Having more I/O makes it a more versatile interface and one that's a bit more reassuringly cased in metal. But the cherry on top is undoubtedly the DC-coupled outputs which, while not perfect, are going to open up a whole other way of interacting with my gear.

Software Bundle

NI supply a ridiculous amount of software with these boxes. Along with the Komplete Start collection that anyone can download, you get the very decent Monark analogue mono synth, the Mod Pack modulation effects, Replika delay plug-in and Solid Bus Compressor. Along with the obligatory Ableton Live Lite you also get the full version of the Maschine software with a limited library and Traktor LE 3. And don't forget the £22$25 voucher to spend in the store.


  • Sleek looks.
  • USB powered.
  • MIDI ports.
  • Good driver performance.
  • DC–coupled outputs.


  • No monitor outputs other than headphones.
  • Using outputs for CV not as smooth as it should be.


A good–looking and nicely featured USB–powered audio interface that has special skills in Eurorack manipulation.


£189 including VAT.