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RME MADIface XT & USB

Audio Interfaces
By Matt Houghton

RME MADIface XT & USB

These compact devices boast more digital I/O than any other USB interface.

Given their reputation for innovation, it's perhaps not surprising to learn that RME have produced the first audio interface to take advantage of the high data-transfer rates offered by the USB 3 standard. One of the main attractions of the MADI protocol is its ability to deliver huge numbers of audio channels through a single cable, and both of the two interfaces under review here take full advantage. Even the smaller MADIface USB can deliver an impressive 128 channels of digital I/O (64 in, 64 out) over USB 2, and is equipped with both optical and coaxial MADI connectors. The only other dedicated USB 2 MADI interface I'm aware of, Digico's UB MADI (reviewed in SOS June 2013), can access only the first 48 channels of a MADI feed, only at 48kHz, and only via coaxial connectors. The MADIface USB also doubles up as a MADI repeater or stand‑alone format converter.

For more than 64 channels each way, you need multiple MADI connections. Until now, this was only possible if you had one of the PCIe‑based MADI systems offered by RME and others, or one based on Ethernet, such as Focusrite's Rednet (and the latter generally also use a PCIe connection in any case). RME's MADIface XT changes that. It boasts stereo AES3 I/O, two analogue mic/line inputs, a pair of analogue outputs on line‑level XLRs, plus a quarter‑inch stereo headphone jack, and three pairs of MADI connectors (one coaxial, the other two optical). That takes the total audio channel count to 394: 196 inputs and 198 outputs. As if that weren't enough, there's also MIDI over MADI and word-clock in and out. The primary means of connecting to a computer is via USB 3, but if 70 or fewer channels are required, the MADIface XT can operate via a lowly USB 2 connection. It also has an on‑board PCIe port, which means that, via a suitable adaptor, it should be capable of operation via Thunderbolt.

Both interfaces cater for 24‑bit audio. The MADIface USB supports sample rates from 44.1 to 192kHz, while the XT does likewise, but can also run at 32kHz. The devices can operate in single‑speed mode for sample rates up to 48kHz, double speed for 88.2 and 96kHz, or quad speed for 176 and 192kHz audio, with a commensurate halving or quartering of the number of audio channels in the last two instances. These last two modes use the S/MUX protocol to split the audio data across multiple MADI channels. 'Native' 96kHz MADI is also supported, though the channel count is again restricted to 32 per MADI port, as when using S/MUX, due to the available connecting cable/fibre bandwidth. There is no 'native 192kHz' mode in the MADI spec, so S/MUX 4 is the only option for quad rates.

Layout

Despite the channel count, the MADIface USB is compact and easy to use. There's a USB port on the rear, and the two pairs of MADI connectors on the front. A small LED tells you when it's connected to a computer and powered via USB, and two further LEDs inform you when sync has been achieved with connected equipment. As far as the hardware goes, that's it.

With its mic/line 'combi' inputs and headphone socket on the front panel, the XT version looks more like a typical audio interface. You'll also find clip, signal‑present and phantom‑power LEDs for the analogue input channels, dual‑purpose volume and menu‑navigation controls, four buttons, and a small but high‑resolution colour display. Around the back are the various connectors for the I/O discussed above, a power on/off button and a connector for RME's separately available ARC (Advanced Remote Control) unit. MIDI and AES are delivered and received through a supplied breakout cable.

Hardware & Software Control

A considerable degree of control is offered via the MADIface XT's front panel, courtesy of the two encoders, four buttons and screen. This includes control of phantom power, channel polarity, mic preamp gain (up to 60dB) and more besides.

The MADIface XT can also (and the MADIface USB must) be set up and controlled by RME's TotalMix FX software, which is, as Sam Inglis remarked in his review of RME's Fireface UCX, sufficiently powerful to rival some dedicated DAWs. It's evolved a lot from the non‑FX version of TotalMix I use with my Fireface 800: it now offers MIDI and OSC control options, for example, and the ability to scale the mixer, enabling you to fit more channel meters on the screen: an important consideration with these high-channel‑count interfaces. It boasts very flexible DSP routing that allows any input to be patched to any of the outputs (and also to multiple outs).The MADIface XT's back panel is certainly more populous than the USB's, which merely features a single USB type-B port.The MADIface XT's back panel is certainly more populous than the USB's, which merely features a single USB type-B port. With the XT (but not the USB), on‑board EQ and dynamics (compressor, expander and 'auto‑level', the last of which allows you to specify a maximum gain and a fixed amount of headroom) can be applied to all the input and output channels, and global reverb and delay effects are available. It's all fairly intuitive, but, unfortunately, channels can't separately address the global delay and reverb: one send control per channel routes the signal to both effects. That's fine for setting up things like cue mixes, but it's not going to form the heart of a modular digital mixer setup. When asked, RME said that this is due to the amount of DSP required to do all the routing and effects processing, which is fair enough.

Mostly, TotalMix FX is superb. Not only do you still get the Matrix routing editor, which is invaluable when working with so many channels, and control of functions like phantom power for the XT's preamps, but there are facilities specific to multi‑port MADI interfaces, such as the ability to treat the inputs and outputs as a single group, or to list them by MADI port. My only real reservation is that TotalMix FX is rather dark, particularly when you consider that these interfaces will be used with laptops. My 15‑inch MacBook Pro Retina screen is better than average, and my eyesight is not the worst in the world, but, while the meters are bright enough, the software would have been far easier to use if the colour‑scheme, brightness and contrast had been adjustable.

Another piece of software, Fireface USB Settings, governs how the devices are configured, allowing you to independently select the MADI output format carried by the coaxial and optical connections, select the clock source and sample rate, and so on. It also informs you whether the connected devices have sync'ed as they should. Finally, RME's useful and fully featured DIGIcheck digital-audio measurement and analysis software, which we've described in SOS before, is included. Multi-client ASIO/WDM/Core Audio functionality is supported.

In Use

Having downloaded the latest driver and firmware from RME's web site, I performed the firmware flash on both units. The updater is a small download and tells you whether the device's firmware is current before you choose to update. The driver installation required a shutdown and restart, but was otherwise quick and pain‑free. After hooking up the MADIface USB to my MacBook Pro, booting my DAW and selecting the RME driver, the interface's I/O all became available. Hooking up a MADI A‑D/D‑A converter (a Ferrofish A16 Ultra MkII with MADI option), things sync'ed as they should. So, the MADIface USB is a simple, hassle-free USB 2 MADI interface. No problems here!

Despite the additional features of the XT version, setup was similarly hassle free. After hooking up the various cables — a USB 3 cable,RME's TotalMix FX software.RME's TotalMix FX software. the AES/MIDI breakout loom, the power supply and the (not supplied) optical MADI cable — the only scary thing was the daunting number of channels that appeared in my DAW's drop‑down list! The drivers are common to both MADIfaces, so there was no need to install anything more for the XT. In fact, having disconnected the MADIface USB with TotalMix still open, I plugged in the MADIface XT and TotalMix kindly informed me that the channel settings had changed and asked me to choose whether I wanted to sync the interface to TotalMix or vice versa, which was reassuring. I then connected both MADIfaces to the laptop, each to a different USB port. It's not possible to treat the two devices as a single interface in TotalMix (though one could still create an aggregate device in OS X), but I was presented with separate TotalMix windows to control the routing for each device. Consulting the manual suggests that a third device could, in theory, be added in this way.

RME have a well-deserved reputation for the efficiency of their audio drivers, and the default latency of the MADIface XT system was easily low enough to let me play software instruments without any problem when I had a USB controller keyboard connected. And, of course, TotalMix provides comprehensive near‑zero-latency monitoring of input signals should you need to set up cue mixes and so on.

Conclusions

There's a lot of publicity about the MADIface XT being the world's first USB 3 interface, and it's nice that RME made that leap for good, technical reasons (the bandwidth requirement) rather than as a marketing gimmick. It's great that the MADIface XT also supports PCIe/Thunderbolt and USB 2, as this extends its utility and should widen its appeal. The build quality is good, the I/O comprehensive, the manual complete, the supporting software excellent and everything about the XT is quick and intuitive. My mild criticisms of the TotalMix FX UI aside, I can't fault this interface.

It may surprise you, therefore, that the MADIface USB is my favourite of the two. Why? It's just so simple and it fills a niche in different markets: anyone working with MADI in broadcast systems can now use it with a laptop. And its price means that MADI is at last within reach of the project studio; anyone wanting a means of hooking up a laptop to a large analogue console or racks and racks of outboard has the potential to access more I/O than they could wish for. The addition of a stereo D‑A for headphone monitoring would be a nice touch but would add to the cost (perhaps there's an opportunity for a third model there), but judged on what it is, the MADIface USB can't be faulted.  

Alternatives

Digico's UB MADI is the only other dedicated USB-to-MADI converter currently available. It's more expensive and offers fewer channels and features than the MADIface USB. The Antelope Audio Orion 32 is a more fully featured audio interface than the MADIface XT, but doesn't offer as many MADI channels, either per se or via its USB 2 connection.

MADI Modes

When MADI was conceived in 1991, it was designed to carry 56 channels of 24‑bit audio, passed serially (one channel after the other) over a single coaxial cable or optical fibre. The maximum data that can be passed over the cable is limited to roughly 100Mb/s, and that limits audio sample rates to between 32 and 48kHz, although ±12 percent varispeed around the nominal sample rate was also allowed. In 2003 the MADI format was revised in light of the fact that few users needed varispeed but many wanted more channels. So a new 64‑channel mode was permitted at fixed 32, 44.1 or 48kHz sample rates. This revision also included the option to run 28 or 32 channels at 88.2 or 96kHz sample rates, known as the 'native 96kHz ' mode. Essentially, pairs of channels are used together to carry a single double‑rate audio signal. The actual MADI interface rate remains at 44.1 or 48kHz, though, to comply with the maximum 100Mb/s capability of the coaxial or fibre connection.

An alternative high‑sample-rate MADI scheme is obtained by employing the ADAT S/MUX 2 or S/MUX 4 data‑encoding formats. Again, these halve (or quarter) the number of audio channels to allow double (or quadruple) the number of audio samples to be squeezed into the same total space. Thus a standard MADI format with S/MUX 2 conveys 32 channels of 88.2 or 96kHz audio, and S/MUX 4 conveys 16 channels of 174.4 or 192kHz audio, while the MADI interface itself operates at base sample rates. Hugh Robjohns

Pros

  • Huge channel count.
  • Compact and easy to use.
  • Excellent build quality.
  • TotalMix FX & DIGIcheck software.

Cons

  • It's a small thing, but a stereo analogue output on the MADIface USB would have been useful.

Summary

The world's first USB 3 interface, the MADIface XT, takes advantage of the protocol to deliver a staggering number of audio channels. Its sibling, the MADIface USB, is the most affordable means of getting MADI in and out of a laptop.

information

MADIface XT £1749, MADIface USB £699. Prices include VAT.

Audio AG +49 8133 918170

info@audioag.com

www.audioag.com

www.rme-audio.com

MADIface XT $2649, MADIface USB $999.

Synthax Inc. +1 754 206 4220

info@synthax.com

www.synthax.com

www.rme-audio.com

Test Spec

  • Early 2013 MacBook Pro Retina 15‑inch, OS 10.9.2 (Mavericks).
  • Reaper 4.591 64‑bit and Cubase 7.5.2 32‑bit.
  • MADIface Firmware 19.
  • RME Driver v1.95.
Published July 2014