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RME Fireface 400

Firewire Audio & MIDI Interface By Tom Flint
Published July 2007

RME Fireface 400

RME pass down some of the excellent features of their Fireface 800 to the more affordable 400 model, but have they cut any corners in doing so?

The latest Firewire interface from RME is very much a slimmed-down and redesigned version of the powerful Fireface 800, featured in the December 2004 issue of SOS. Like the 800, the Fireface 400 handles analogue and digital audio using a diverse and comprehensive array of I/O and supports sample rates up to 192kHz. This time there are 10 digital ins and outs, plus a further eight balanced analogue ins and outs, totalling 36 channels altogether.

At present, competition is fierce in the Firewire interface marketplace, so RME have ensured that the 400 excels in certain key areas. One of the things setting it apart from the competition is its extremely flexible routing arrangement, controlled via a 648-channel matrix and software mixer. This setup has allowed RME to squeeze a lot of functionality out of the 400's I/O options and means that the 400 can be used in ways beyond its primary role as a computer interface. If, for example, its inputs are routed directly to its outputs, it can perform as a four mic-channel preamp. It can also be used for signal format conversion from S/PDIF to ADAT or vice versa, as a submixer, or as a studio's digital master clock. Admittedly, there are other products with similar functionality (see the 'Alternatives' box), but the 400 matches the best of them in this department.

The 400 also benefits from technologies RME have developed for their high-end products. Most significantly, as far as audio quality is concerned, the 400 uses RME's propriety Steady Clock technology (already implemented on their ADI-648, HDSP 9632, HDSP MADI, ADI2, ADI4 DD and Fireface 800 products) for clocking A-D/D-A converters and all synchronisation tasks. In action, Steady Clock dramatically reduces jitter when slaving to incoming word clock or code embedded in ADAT or S/PDIF signals, redistributing a cleaned-up, frequency-matched signal.

Another key feature of Steady Clock is that it is able to lock up quickly and suppress jitter even when the sample rate is being dramatically varied in real time. To achieve this feat it uses just one quartz oscillator, together with something called Direct Digital Synthesis (DDS) to speedily create sample frequencies anywhere within a range of 28 to 200kHz. The supplied control software provides a choice of 27 preset rates, plus Coarse and Fine sliders that, when Master Mode is active, can be dragged in real time to change the pitch/speed of all synchronised devices. This flexibility will be especially welcome to those working in post-production environments, where frequency tweaks are used to compensate for the frame-speed discrepancies between different film and video formats.

It's also worth mentioning that RME claim to be the only company using their own Firewire chip design rather than a third-party DSP chip. The reason for this is that Firewire has limited data-handling abilities, so the 400 uses an FPGA (Field Programmable Gate Array) system to improve things, effectively increasing bandwidth, enabling lower latency operation and reducing data errors.


There seems to be a lot of Firewire interfaces on the market at the moment, so competition is tough. Of those selling at around the £500 mark, the main alternatives to the 400 are the Focusrite Saffire Pro 26 I/O, TC Electronic Konnekt 24D, Presonus Firepod, Digidesign M Box 2 Pro Factory, and MOTU's 828 MkII, Traveller and 8Pre. Some of the above are offering a suite of free software recording and processing tools, as well as 192KHz operation, but word clock is slightly less common.

The Saffire Pro comes with a bundle of Focusrite's respected processor plug-ins and has two sets of ADAT I/O and word clock, but scores over the 400 by offering eight XLR ins. Digidesign's M Box Pro has less I/O, does not support 192kHz operation and has no external sync at 88.2 and 96kHz sample rates. It does, however, have word clock and comes with highly desirable Pro Tools LE and Ignition Pack sound generating and processing tools.

The MOTU 8Pre lacks S/PDIF and word clock but includes eight XLR mic inputs/preamps and eight channels of ADAT I/O at 96kHz, as well as RME-style stand-alone functionality. The 828 MkII adds SMPTE in and out, whereas the Traveller can handle 192kHz.

The Konnekt 24D's trump card is the inclusion of Powercore DSP effects, and the company also throw in a copy of Cubase LE. This is another device that supports 192kHz operation, but provides less I/O to play with. Most significantly, perhaps, it uses TC's proprietary DICE II chip with Jitter Elimination Technology, a rival to RME's Steady Clock.

Product Overview

The Fireface 400 is a robust half-rack interface, which appears to have a pretty standard set of features when viewed from the front, although the back panel is abnormally packed with I/O. Situated on the front are the first four inputs, two of which are of the combi socket type,which accept either XLR or quarter-inch jack connections. Front-panel feedback is offered by red clip and green signal indicator LEDs, plus another showing whether 48 Volt phantom power is active. Unusually there are no corresponding knobs or buttons for setting suitable mic or line input levels, the case being that these (and all the rest of the 400's levels) are controlled using just one assignable front-panel knob. The encoder in question actually doubles as a switch, a press of which causes the neighbouring two-digit display to flick between an I/O menu and channel level value. According to the status (as indicated by a further two LEDs), turning the knob changes either the level or the input/output selection. Of course, full control is also provided by the complementary software mixer, but we'll come to that in a moment.

Also on the front, with their own clip and signal LEDs, are two of the six balanced quarter-inch jack Inputs. These provide up to 18dBu of gain, have 6dB pads and are intended for instrument and line use. As you'd expect, the headphone output is also on the front, but the software mixer enables independent control of both channels, so this can be used as an alternative pair of outputs. The only other section on the front comprises a set of LED indicators showing the current synchronisation and MIDI setup.

Things get more interesting around at the back, where the vast majority of the I/O is found. In fact, there's not room for everything so the 400's two-in/two-out MIDI connectors are at the end of four 12-inch breakout cables which converge and connect to the unit via a single socket.

Also on the back are the four remaining quarter-inch jack inputs, plus a row of six balanced outputs. None of these are specifically labelled as master outputs, but the reason for this is that hardly anything is internally hardwired, so any of the outs can be assigned the task.

The two ADAT optical sockets provide the bulk of the digital I/O, but the eight channels are reduced to four when sample rates over 48kHz are used. This is a restriction of the ADAT format and common to all manufacturers. To achieve 96kHz, a workaround technique called Sample Multiplexing is applied, in which two channels are used for each audio stream. This becomes active when the 400's sample Settings are changed to DS (Double Speed) mode.

Flanking the ADATs are the BNC word clock and RCA phono S/PDIF inputs and outputs, plus the two Firewire ports, one of which can be used to begin a daisy-chain of up to three 400/800 units.

Finally, there is a power adaptor input for use when connection has to be made to a device only offering the non-powered four-pin type of Firewire connector, as is the case on many laptops. Otherwise, the 400 is happy to take its power via a six-pin lead.

Staple Software

The software mixer provides a visual overview and control of all the Fireface 400's 36 input and output channels.The software mixer provides a visual overview and control of all the Fireface 400's 36 input and output channels. In terms of software, the Fireface 400 package includes several 400-optimised programs which were originally developed for the 800 and other RME hardware. The Fireface mixer, called Total Mix, displays all 18 input and output channels plus a further 18 extra playback tracks, and provides the user with mixer controls for all of the above. It is from the mixer page that the monitoring setup is controlled and things like level, pan, mute and solo are adjusted. Eight preset memories allow the user to save and recall complex routings when required, and it's even possible to do things like re-name the channels.

In addition to the mixer is a 648-channel Matrix page presenting the 18 hardware inputs and software outputs on one axis and the real outputs on the other, and it is by activating the boxes at the crossover points that routing can be established.

Separate from Total Mix is the all-important Settings program, where all the synchronisation and gain presets are managed and monitored. Elsewhere on the Driver CD is a free copy of RME's DIGI Check software, which provides all sorts of useful analysis and metering tools for scrutinising the audio data stream.

System requirements are modest. In terms of hardware, a Pentium III PC with an 866MHz processor, or Mac G4 Dual 867, will suffice. For Mac, OS 10.3 is the starting point, while PC owners need to be running Windows 2000 SP4, XP, XP64, Vista or Vista 64.

The Fireface In Action

Getting started with the Fireface requires the installation of the Mixer and Settings programs from the supplied CD, which then, on my Windows XP system, become accessible in the Taskbar menu at the bottom of the screen.

The default Mixer setup is a good starting point, and in order to fully exploit Fireface's potential it's important to quickly master the software. The mixer is more complex than it first appears, simply because there are so many routing options. Here, for example, 18 auxiliary send channels make it possible to set up nine independent stereo submixes, one of which is routed to the headphone socket. A useful submix view makes it relatively easy to oversee the balance fed to each pair of outputs, although understanding how the software channels relate to the hardware ins and outs is not immediately obvious. The Matrix window is probably the easiest way to establish routings, and provides a single snapshot view of how things are patched.

Of all the mixer's functions, it's the monitoring facilities that seem especially well thought out. For example, clicking the 'Dim' button instantly reduces the main output level by a preference-specified amount, so that unexpectedly loud audio can be neutralised. This is particularly handy if you need to hold a conversation or take a phone call. Elsewhere on the page are three 'Monitor Phones' buttons, which re-route the remaining paired outputs to the main monitoring, so that submixes sent to external recording devices or performer's headphones can be auditioned.

The Fireface's rear panel is, as you can see, absolutely packed to the gills with I/O.The Fireface's rear panel is, as you can see, absolutely packed to the gills with I/O.As far as audio quality is concerned, there can be few complaints. RME informed me that the 400 has new programmable A-D converters — I can't imagine there was much wrong with the 800's ones — but both these and the preamps are very good. I found the sound to be bright and clear without being harsh, allowing the finer detail of mixes to cut through and be noticed.

Noise levels throughout the system seem to be exceptionally low. When I turned the headphone output up to maximum, for example, I could hear absolutely no noise whatsoever, even through my high-end Sony MDR7509 cans. Impressively, even when playing audio with the faders pumped up full, there was no obvious audio distortion other than the inevitable digital clipping.

I hooked the Fireface up to my trusty old Yamaha AW4416 to check the word clock and Auto Sync functionality, and bussed a 16-track song to the eight ADAT channels of the installed Waves Y56K card's optical output. The AW has a varispeed control, so, with the 400 in Auto Sync mode, I played the track and speedily swept the rate, finding that the Fireface was perfectly able to sync via the ADAT signal without any glitches. I then tried slaving the Yamaha to the word clock in and varied the AW using the DDS Coarse and Fine sliders, and I found that worked well too. As for the Setting pages, where the clock's DDS function is controlled, they proved very effective and easy to use

The lack of dedicated hardware controls is perhaps one area where the 400 seems to be lacking, from a user's point of view, yet considering there's just one knob and a two-digit display, programming works surprisingly well. At most it takes just a few seconds to find and adjust any of the variables.


At present, Firewire looks set to be around for some years to come, so something with this much in-built flexibility and comprehensive I/O can be viewed as a bit of a long-term investment.

RME state that they want the 400 to sit at the very top of the range of computer-based audio interfaces, and, in terms of sound quality and its clocking/synchronisation abilities, it must be close. There is, however, a lot of competition in this area of the market at the moment (see the 'Alternatives' box), and even Steady Clock is rivalled by TC Electronic's JET (Jitter Elimination Technology).

Whether they are right at the top or not, it is evident that RME are extremely concerned with audio integrity; possibly more so than the vast majority of their customers. It's certainly reassuring to know that this company are taking care of issues that are not immediately apparent to the end user.

As far as feature omissions are concerned, it would perhaps be nice to have a few more XLRs, although it's hard to see where they could be squeezed in. Some people will miss having dedicated level knobs for the preamps, particularly those users recording something not immediately adjacent to their computer. The front-panel knob and display partnership is a surprisingly efficient replacement, but in some situations using a MIDI controller as a remote might be the answer.

It also could be argued that a second set of ADAT I/O should have been added, as this would enable the 400 to handle eight channels at 96kHz.

RME are not giving away free software recording programs, processor and effects plug-ins or even soft synths, as seems to be the policy with some of the competition, but they are offering first-rate audio recording, mixing and playback, and sometimes that is the most valuable thing to have. 


  • Well made and cleverly thought out.
  • Word clock I/O, Steady Clock and Auto Sync work wonderfully.
  • Numerous useful configuration options.
  • Very high-quality audio.
  • Second Firewire port for chaining devices.


  • No dedicated hardware level controls for I/O.
  • The routing takes a bit of getting used to.
  • No XLR outputs and only two XLR inputs.
  • The single pair of ADAT ports limits the I/O count above 48KHz.


The Fireface 400 sets a very high standard in terms of audio quality and synchronisation. Its flexibility and I/O options mean that owners are unlikely to find many situations beyond its scope.


£549 including VAT.

Synthax Audio UK +44 (0)1664 410600.

+44 (0)1664 410999.