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RME Fireface UC

USB 2 Audio Interface By Sam Inglis
Published September 2010

It may be small, but the RME Fireface UC is very powerful and boasts astonishingly low latency.

RME Fireface UC

RME have been one of the most forward‑looking developers of audio interfaces. They were among the first to recognise the potential of the ADAT optical format, and more recently have brought the high‑end MADI protocol to the semi‑pro market. RME also enjoy an enviable reputation for the quality of the driver software that powers their Firewire and PCI interfaces. However, the new Fireface UC is the first RME device to connect via USB 2. Can it meet the same high standards for stability, flexibility and low‑latency performance?

Separated At Birth

Externally, the Fireface UC is at least 90 percent identical to the existing Fireface 400, which was reviewed by Tom Flint in SOS July 2007 (/sos/jul07/articles/rmefireface400.htm). It is, in other words, a 1U, half‑rack‑width device with comprehensive audio and MIDI I/O. This is summarised in the 'Vital Statistics' box, and is exactly as it is on the Fireface 400. Perhaps the most distinctive feature of both units is that there are no analogue controls at all. A single, multi‑purpose encoder, which also acts as a button when pressed, sets all input and output levels, including the gain of the two mic preamps. All its functions are also available from the software control utilities.

Whereas the Fireface 400 can be bus‑powered if your computer has a suitable six‑pin Firewire socket, the UC relies on the supplied 'line lump' power supply. Thus, although it has the same small switch on the rear panel as its sibling, this has been repurposed for the UC as an on/off switch, which would be inconvenient if the unit was rackmounted. Whereas the 400 has a second Firewire socket for daisy‑chaining multiple units, here there's only a single USB socket. It is, however, possible to attach up to three Fireface UCs to a single computer if you have enough free USB ports.

The UC comes with all of RME's sophisticated and mature software utilities. These include a simple control panel for selecting clock source, mic-amp gain and the like, and the anything‑but‑simple Total Mix. Total Mix is an absurdly comprehensive mixer which, in effect, allows you to route every input to every output, in whatever degree you choose. This mixing takes place within the interface rather than your computer, so there is no additional latency on top of the minuscule amount imposed by the A‑D and D‑A conversion processes. Total Mix supports presets, keyboard shortcuts, mono monitoring, MIDI control, and both 'loopback' and subgroup recording, to name but a subset of its features. About the only restriction I can spot is that the channels in the main virtual mixer always address stereo pairs of outputs. If you wanted to set up a truly independent mix for every mono output, you'd have to use the alternative Matrix view, but I can't imagine that many people would need to do that very often.

How Low Can You Go?

The Fireface UC's busy rear panel. Inputs 1-4 haven't been forgotten — they're found on the front of the unit.The Fireface UC's busy rear panel. Inputs 1-4 haven't been forgotten — they're found on the front of the unit.

In many recording situations, Total Mix makes issues of recording latency irrelevant, giving you total freedom to set up as many monitor mixes as you have outputs. However, there are still those to whom latency figures are crucial, most obviously musicians who depend on software synths and samplers. And so, to complement what is surely the most comprehensive latency‑free mixer to be found outside of a Pro Tools HD rig, RME also provide drivers that are claimed to offer unparalleled low‑latency performance.

Usually, my Dell laptop is to rock‑solid low‑latency performance what Britain is to international ski‑jumping. With most other interfaces I've tried, a 256‑sample buffer at 44.1kHz is pushing it, so I was impressed that the RME drivers continued to work well down to 96 samples. I can well believe that on a machine that is less Eddie the Eagle and more Thomas Morgenstern, the lowest, 48‑sample setting would be practical.

On the Mac, RME claim that the Fireface UC can operate at an even more impressive buffer size of 14 samples. I wanted to see that for myself, so I hooked it up to an Intel iMac at the SOS office, running Mac OS 10.6, and fired up my copy of Reaper. I gingerly entered '14' into its Block Size field, expecting to be greeted by a wall of digital noise, but remarkably, it worked without a hitch, and I was able to play back and record audio with no problems at all, at a reported latency of 1.3ms. This was mighty impressive, especially for an off‑the‑peg computer that has never been tweaked or configured for audio use.

Summing Up

For a unit with an external power supply, the Fireface UC gets surprisingly hot to the touch, presumably because so much is packed into such a small case. It coped admirably with everything I could throw at it, including a lengthy drum‑recording session with a preamp attached via ADAT, and overdubbing using its own preamps and instrument sockets. The sound quality is as pure as you'd expect, imposing neither any character of its own nor any unwanted noise or distortion.

As a way of offering almost all the Fireface 400's good qualities (apart from bus powering) over USB rather than Firewire, the Fireface UC succeeds admirably. There is very little to criticise, although naturally not all of RME's design choices will suit everyone. Personally, I'd be happy to sacrifice the UC's compactness and move to a full rack‑width unit if that permitted the inclusion of an internal power supply, hardware metering, an extra headphone socket, more hands‑on controls, and MIDI sockets on the unit itself rather than the flying cables currently used. However, that would no doubt add to the cost, and I'm sure there are many for whom the UC's small size is a major plus point.

Speaking of cost, there's no shortage of multi‑channel interfaces around, and it is certainly possible to obtain more I/O for less cash, especially if you have the option to use Firewire as well as USB 2. Focusrite's Saffire Pro 40, for example, boasts eight mic preamps plus all of the features mentioned above, and even if you need to buy a Firewire adaptor to use it, it'll cost you less. But this is a case where one needs to be wary of paper comparisons, because they underplay the significance of RME's driver software and DSP mixing utilities. If you value features such as the absolute freedom to route anything to anywhere, the ability to use soft synths at negligible latencies and, above all, confidence in your system to remain stable in the middle of an important session, RME's Fireface should be your first port of call.  


Probably the UC's most direct rival is the MOTU UltraLite Mk3 Hybrid. With a similar complement of analogue I/O, it too features particularly comprehensive on‑board DSP mixing, but with effects, and can connect via Firewire or USB 2 for maximum flexibility. It's also cheaper than the UC, but then it does lack the RME unit's ADAT and word clock I/O.

Vital Statistics

  • USB 2 audio & MIDI interface.
  • Compatible with: Mac OS 10.5 and above, Windows XP SP2, Vista and 7.
  • Analogue inputs: eight (two combi XLR/jacks, two front‑panel instrument/line jacks, four line jacks).
  • Analogue outputs: eight (six rear‑panel jacks plus front‑panel stereo headphone jack).
  • Mic preamps: two.
  • Digital I/O: word clock in and out, stereo coaxial S/PDIF, optical S/PDIF or ADAT.
  • Other I/O: two MIDI Ins and Outs.


  • Superb low‑latency performance.
  • Brings all of the features for which RME are renowned to the USB format, including the Total Mix utility.
  • Very portable.
  • Excellent sound quality.


  • External power supply always needed.
  • Small size dictates some compromises over physical layout and design.


The USB version of RME's Fireface 400 is every bit as impressive as the original.


£709 including VAT.

Synthax Audio UK +44 (0)1923 693756.


Synthax Inc +1 954 626 0674.

Test Spec

  • RME Fireface UC hardware revision 86.
  • Dell Inspiron laptop with 2GHz CPU and 4GB RAM, running Windows XP SP2.
  • Apple iMac with 2.16GHz Intel Core 2 Duo CPU and 2.5GB RAM.