RME Digi 9652 Project Hammerfall

Project Hammerfall is an unusual name for a soundcard — but then RME's new card is somewhat out of the ordinary. Martin Walker enters a world of sample‑accurate sync and minimal latency.

The ADAT digital interface standard has is now in widespread use on a far greater variety of systems than Alesis's original tape‑based digital multitrackers. Most digital mixers, for instance, provide digital I/O in this format, and it's now possible to set up a very powerful recording system which uses ADAT interfacing to combine the mixing facilities and analogue I/O of a digital desk with the recording, sequencing, editing and processing capabilities of a modern computer.

Indeed, many of those musicians who actually own ADAT recorders must be looking enviously at the facilities provided by the latest computer‑based audio sequencers. The ability to see the waveforms and edit them right down to sample accuracy, as is possible with such graphical random‑access systems, makes the process of editing a lot easier. However, ADAT machines still have their own virtues — in particular, they are very easy to use, especially to those familiar with analogue multitrackers. So, rather than sell them and move to a wholly computer‑based system, many existing ADAT owners are likely to consider running them in parallel to gain the best of both worlds — a straightforward and reliable tape‑based recording and playback system synchronised to a computer supporting MIDI and audio tracks.

To link either an ADAT or an ADAT‑format digital mixer to a computer, you need a computer soundcard with an ADAT‑compatible interface. SOS has looked at several such cards before: the Alesis ADAT Edit reviewed in last month's issue supports a single eight‑channel ADAT interface, while the Sonorus StudI/O reviewed in the September '98 issue supports two. Like the MOTU 2408 reviewed in February '99, however, the RME DIGI 9652 (aka Project Hammerfall) under review here can support up to three ADAT interfaces simultaneously. Another of its main selling points is its comparatively low price — for £499, you effectively get an interface ideal for connecting your computer to up to 24 ins and 24 outs of multitrack digital recorder or mixing desk, along with a single stereo digital in and out for mixdown use. The MOTU system, by comparison, costs £999, though its I/O is mounted in a separate breakout box and includes eight analogue inputs and outputs with 20‑bit converters (Project Hammerfall has no analogue I/O at all).

The 9652 is also the first soundcard (to my knowledge) to be released with ASIO drivers that conform to the new ASIO 2.0 specification, as implemented in Steinberg's new Cubase VST version 3.7 for Windows (see review on page 160). This provides 'zero'‑latency monitoring inside Cubase VST by automatically routing the incoming audio signal to the equivalent hardware output during recording, completely bypassing any delays caused by software processing. However, even without this feature, the Hammerfall drivers still provide extremely low latency, down to a very impressive 3mS given a powerful enough host computer. In addition, it can transfer digital data to and from ADAT machines with sample‑accurate sync, and is even capable of 24‑bit 96kHz operation with other digital devices such as DVD.

Overview

The DIGI 9652 Project Hammerfall soundcard is one of the few to provide sample‑accurate sync, enhanced 'zero'‑latency monitoring and support for 26‑in/26‑out operation.

RME may be a new name to some SOS readers, but the Germany‑based company has been quietly making a name for itself with the high quality DIGI range of soundcards, now distributed in the UK by Digital Media. In fact, readers with good memories may remember me mentioning the excellent selection of audio test files available from the download page of the RME web site in my March '98 PC Notes column. I still use some of these (particularly the 24‑bit ones) as part of my test procedure for each and every soundcard I review for SOS.

The RME '96' range includes the S/PDIF‑only DIGI 96 soundcard (£299), the DIGI 96/8 with added ADAT I/O (£349), the DIGI 96/8 PRO with a 20‑bit D‑A converter (£399), and the DIGI 9/8 PAD with both A‑D and D‑A converters (£449). The DIGI 9652 reviewed here is the latest and greatest card in the range, and provides three 8‑channel ADAT optical inputs and three 8‑channel ADAT optical outputs, along with a stereo S/PDIF input and output, word clock input and output, and a 9‑pin ADAT sync input.

All of the 9652's digital audio inputs and outputs are capable of 24‑bit 96kHz operation, albeit by a circuitous route. Since the ADAT optical spec only supports sampling frequencies of up to 48kHz, RME use what they term 'sample split', and distribute the doubled bandwidth for 88.2kHz and 96kHz sample rates between two channels, giving a halved channel count of 12 inputs and 12 outputs along with the same stereo S/PDIF in and out. The name of the card is derived from this 96kHz capability, and the fact that the total number of digital audio channels comes to 52 when running at a sample rate of 48kHz or less.

Installation

The 9652 Settings utility provides concise and easy access to the various options. The buffer size can even be adjusted while the card is in use, which makes it easy to determine the lowest reliable setting for your own computer.

Project Hammerfall is one of the smallest PCI cards I've seen, and at just five inches long should fit in any PC or Mac without a shoehorn. The backplate contains four Toslink optical connectors (for ADAT 1 Input and Output and ADAT 2 Input and Output), along with a 9‑way D‑type connector. To this you attach a short adapter cable which terminates in a 9‑pin flying socket for ADAT Sync In and a pair of in‑line phono sockets for S/PDIF In and Out.

However, as with many recent soundcards, a single backplate is just not enough to house all the required socketry, so RME have placed the remainder on the 'Expansion Board' — a stand‑alone backplate (complete with a small circuit board) that you can fit instead of a blanking plate in front of any empty PCI or ISA card slot. This houses the third and final ADAT 3 Input and Output, along with a pair of BNC sockets for word clock In and Out. Next to these is a useful green LED which lights up when the word clock input has locked to a valid signal. You don't have to install this Expansion board: if you are short of space and happy with the twin ADAT support of the main board, it will happily run by itself.

The main card and expansion board are connected using a supplied three‑inch‑long ribbon cable. RME obviously expect you to place the two next to each other, but I just managed to piggyback one intermediate card to fit the expansion board next to a vacant slot. In a well populated machine you might need to shuffle your existing cards unless RME decide to splash out on a few more inches of cable.

With latencies of 6mS or lower now possible with many modern PCs, the whole issue of latency begins to take on less importance, and if you have a Pentium III machine capable of 3mS latency, you may not even be aware of it at all!

Installation proved to be quite simple in Windows 98, with the usual plug‑and‑play routine of inserting the floppy driver disk when asked. As with the drivers for most professional cards, the actual file sizes are tiny — five files with a total size of 100Kb. It only took me a few minutes to arrive at the desktop along with the extra Hammer icon on my Taskbar to launch the Settings utility. However, when I tried installation in my Windows 95 partition I had various problems getting the card to be recognised, as well as several system‑wide crashes afterwards. RME subsequently confirmed that Windows 95 can't handle the memory requirements of their card, and that the drivers are specifically written for use in Windows 98. I suspect that this may be the start of a new trend.

Setting Up

On reading the User's Guide, you could almost believe that RME have been religiously reading my SOS writings over the last few months. Not only do they provide specifications for jitter (see Brief Specifications box), but they also have a signal‑flow chart showing how the card works, which makes understanding the options much easier. The S/PDIF input and output can both be switched between co‑axial and ADAT (optical) sockets, and the input can also be switched to 'Internal', which allows you to connect the digital audio output from an internal CD‑ROM drive to the 2‑pin connector provided on the soundcard.

The S/PDIF switching is carried out using the 9652 Settings utility shown opposite, and the S/PDIF Output is even more versatile than at first appears. Its co‑axial socket is always connected, but if you tick the 'ADAT 1' box you switch the ADAT 1 optical output from its normal 8‑channel function to another S/PDIF output in parallel with the co‑axial one. The Emphasis box needs to be ticked if you are outputting any recordings that were originally made using 50/15 microseconds pre‑emphasis. This is because the S/PDIF output header information is created from scratch, losing any previously set bits on input signals.

The 'Non‑Audio' tick box should be used when playing back Dolby AC3 signals, since many external decoders such as those in surround sound receivers or digital TVs won't otherwise recognise the signal as AC3. The fourth tick box is labelled 'Professional', and doubles the output voltage levels (from 0.8 to 1.6 Volts), making them suitable for AES‑EBU operation using the co‑axial output with a suitable adapter lead ending in a male XLR plug. The co‑axial input will directly accept the higher levels from an AES‑EBU adapter lead with a female XLR plug. Clever stuff!

When working with any digital audio card, getting the correct clock settings is vital, and any visual feedback here is extremely useful. As I mentioned earlier, a green LED next to the word‑clock input lights up as soon as a valid input signal is detected, which is very helpful. In addition, the Settings utility shows the Sync Check status of all three optical inputs (ADAT 1, ADAT 2, ADAT 3), and the S/PDIF In: 'Lock' and 'No Lock' indicate the presence or absence of a valid input signal, and 'Sync' shows that a valid synchronous input signal is present. The Settings utility also displays under Time Code the information received using the ADAT Sync In socket, so that you can check this against the display on the ADAT machine itself.

Clock Mode determines how everything syncs up. If you have a valid word clock input (such that the green LED is lit) then you can switch to this as the system reference by selecting 'Word Clock', or you can use the 'Master' setting to force the 9652 to run from its internal master clock, in which case all other devices will have to slave to it (either using the embedded clock in the digital outputs, or the dedicated word clock output). However, the easiest option is to select 'AutoSync'. In this mode the card runs by default from its internal clock, but also scans the digital inputs for a valid clock signal. If one is found at any time it switches to this automatically and becomes the slave, allowing 'on the fly' recording. If this happens the Sync Reference is shown in the utility, along with its current sample rate. This can theoretically be anywhere between 25kHz and 105kHz, although I didn't manage to confirm this. If you have more than one input providing a valid sync reference, you can tick a different box in the 'Pref Sync Ref' section to force the issue.

The Audio Buffer size can be adjusted over a wide range to determine the latency value (see the Size Isn't Everything box), but the beauty of the Hammerfall Settings utility is that you can make any adjustment in real time. You don't need to click on any OK button for a change to take effect, and you don't even need to stop recording or playback, even when changing the latency setting.

In Use

Since the 9652 has no analogue I/O, no comments can be made concerning its analogue audio quality, or any measurements of background noise. However, I did have the opportunity to try it out with RME's ADI‑8 Pro Interface, and this gave impressive results, as one might expect from converters with a dynamic rane exceeding 110dBA (see the Partners In Sync box). The 9652 has been initially released with ASIO drivers only, and as such is only currently compatible with those MIDI + Audio sequencers that support this standard, such as Steinberg's Cubase VST and Emagic's Logic Audio.

The ASIO inputs are labelled DIGI9652 1 to 26, and the outputs are arranged in stereo pairs labelled DIGI9652 1, 3, 5 and so on. The first eight channels correspond to ADAT 1, while 9 to 16 are ADAT 2, 16 to 24 are ADAT 3, and finally 26 and 26 belong to the S/PDIF I/O. The S/PDIF connectors are colour‑coded, but it turned out that the preliminary user guide is lying when it claims that the red socket is the output — in fact it's the input. Once I discovered this, everything burst into life.

The Enhanced zero‑latency monitoring provided by ASIO 2.0 and the RME drivers was a real treat: those who select 'Global Disable' in the Monitoring choices of Cubase and arrange your monitoring externally using a hardware mixer will be able to safely return to the Cubase options. 'Record Enable Type' lets you hear the input as soon as the channel is record‑enabled, while 'Tape Type' only lets you hear the input when in Stop or Record mode, but not while playing back. You can't control the monitor level or pan position inside Cubase with the Hammerfall card, but being able to switch the hardware from Cubase transparently is still a major leap forward, and certainly beats having to set up separate soundcard utilities!

However, a little of its thunder is stolen by the low‑latency option. With a suitably powerful PC, a latency of 6mS or even 3mS is possible (see the Size Isn't Everything box), and this made for a very immediate response both when monitoring an audio performance and for playing VST Instruments. I expect latencies of this order to become a prime requirement for many of next year's soundcards. With my Pentium II 300MHz PC I managed to monitor my input signals with 6mS latency, while listening to the input signal with added effects from Waves' Trueverb as a channel effect, plus a Waves REQ 6 'analogue' EQ and RCL compressor running as inserts.

Although some people might grumble about the initial lack of MME drivers, you can see why RME have concentrated on ASIO performance. With latencies of 6mS or lower now possible with many modern PCs, the whole issue of latency begins to take on less importance, and if you have a Pentium III machine capable of 3mS latency, you may not even be aware of it at all!

Sync Stations

To ensure sample‑accurate positioning when transferring audio digitally between devices you need two levels of sync — sample rate (word clock) and sample position (time code). I connected a pair of optical cables between Hammerfall and an ADAT machine, and then set ADAT 1 as the sync reference using the Hammerfall Settings utility (using AutoSync mode to ensure that Hammerfall became slaved to the embedded word clock signal coming down the ADAT optical cable). Timecode sync was then established by connecting the 9‑pin ADAT Sync Out to the Hammerfall Sync In.

Cubase VST 3.7 needs its Timecode Base set to ASIO 2.0, and the Sync button selected on the Cubase Transport Bar. Another setting to check is that your song's sample rate is also set to the same value as that of the ADAT; otherwise Cubase may intermittently drop in and out of sync. With these settings in place, transferring tracks to and from ADAT proved very easy and gave no problems, with the Time Code being correctly displayed in both Cubase and the Hammerfall utility. Being able to monitor with zero latency also helped during these transfers, and I was impressed by the rapid lock‑up time of no more than a second — it can often take three or four seconds with some gear combinations.

The new ASIO 2.0 positioning protocol worked well, and essentially the ADAT and Cubase tracks became a seamless system with sample‑accurate sync between the two sets of tracks. The system must be controlled from the ADAT transport controls, but if you have a suitable conversion box, it's also possible to select 'ASIO 2.0 with MMC' as Timecode Base, and then you can use the Cubase transport bar controls instead. However, I doubt that most musicians will consider having to use the ADAT controls a disadvantage, since a dedicated set of tactile buttons is nearly always preferable to clicking with a mouse.

Final Thoughts

The ADAT 8‑channel optical interface has grown into a versatile general‑purpose interface used not only by ADATs but by A‑D and D‑A converters, digital mixers and other devices. This ensures that the Project Hammerfall card can remain a versatile nerve centre for your studio even if you stop using ADAT recorders in the future, or don't intend to use them at all.

The only other soundcard to my knowledge to currently have ASIO 2.0 drivers is the StudI/O from Sonorus; with its Backplate option you also get sample‑accurate sync, but this only provides support for two ADAT machines rather than three. However, RME are promising two‑card support in future driver updates, and judging by the driver improvements made even during the review period, I fully expect this to happen. The ADAT Sync Input on the second card would of course be redundant, but with a powerful enough computer the combination of two Hammerfall cards would then support six ADAT interfaces for 48‑in/48‑out operation, along with two stereo channels of S/PDIF.

As with any other soundcard, you may need to experiment a little to find the best value for the Hammerfall driver latency to suit your computer, but this is less important with the ASIO 2.0 enhanced 'zero'‑latency option. However, having feasible latency values down to 3mS also makes this an excellent choice for those interested in a multitrack soundcard that can run some of the latest breed of 'real‑time' ReWire and VST Instruments. This is a versatile and impressive product, and at £499 should attract many users.