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Aardvark Direct Pro 24/96

Professional Studio Interface By Martin Walker
Published April 2000

Aardvark Direct Pro 24/96

High‑quality mic recordings and PC soundcards don't normally go together all that well, but this could be about to change with Aardvark's new audiophile breakout box.

Now that so many musicians are working almost exclusively with computer‑based systems incorporating hard disk recording, software synthesis and sampling, an increasing number of them are questioning whether they really do need a complete hardware mixer. However, sales of voice‑channel units are rising in this environment, because the quality of soundcard preamps often leaves a lot to be desired — and there's also a lot to be said for processing signals with EQ and compression while still in the analogue domain.

Enter the Aardvark Direct Pro 24/96. This combination of soundcard and breakout box provides four high‑quality mic/line preamps, four EQ and compressor sections available for recording and monitoring, and a monitor reverb. All effects run on a 24‑bit 80MIPS DSP engine, and therefore neither consume your main processor's power nor suffer from software latency. The Direct Pro has three stereo analogue outputs, S/PDIF In and Out, MIDI In and Out, and all audio I/O is capable of 24‑bit/96kHz operation. What's more, up to four units can be run from the driver software to provide up to 16 simultaneous audio inputs and 24 outputs.

Aardvark have an enviable reputation where audio quality is concerned. Their products may not be the cheapest around, but it's soon obvious that they mean business — all the Direct Pro's delicate audio components, including the preamps and converters, are housed in the weighty breakout box, while the processing on the PCI card is well shielded to withstand the often harsh environment inside your average computer.

Aardvark have an enviable reputation where audio quality is concerned. Their products may not be the cheapest around, but it's soon obvious that they mean business...


Aardvark Direct Pro 24/96

The Direct Pro 24/96 PCI host card is six inches long, and the majority of its components, including the DSP processor, are concealed beneath the resin‑potted shielded casing. On its backplate are a pair of gold‑plated phono sockets for S/PDIF input and output, and the ubiquitous 25‑pin D‑type port for linking to the interface box. A six‑foot shielded 25‑way cable with locking connectors is supplied and Aardvark have also tried 12‑foot cables with good results, though they're not on the price list.

The external breakout box is about 2.5 x 7 x 8 inches (h x w x d), with a 3mm‑thick solid aluminium case for strength and shielding which would probably survive being run over by a car. Most people will no doubt plonk this breakout box on the desktop, but for professional use Aardvark also sell two versions of a custom 2U rack shelf for the unit: one houses a single Direct Pro breakout box, while the second houses two sitting side by side, but both are currently rather expensive.

On the front panel are four dual‑purpose mic/line inputs, each of which uses a Neutrik combi jack/XLR socket. The jacks can accept either balanced signals at +4dBu level, or unbalanced ones at ‑10dBV. The outer XLR socket for mic levels connects to an internal preamp allowing up to 75dB gain, while a single latching button on the left‑hand side of the panel provides 48V phantom power to all four mic inputs simultaneously. To complete the front panel there is a stereo headphone socket over on the right optimised for 60‑150Ω phones, along with a green power LED.

With six analogue outputs and four analogue mic/line inputs complementing the built‑in DSP, the Aardvark Direct Pro 24/96 should find a lot of appeal amongst musicians who want an all‑in‑one solution.With six analogue outputs and four analogue mic/line inputs complementing the built‑in DSP, the Aardvark Direct Pro 24/96 should find a lot of appeal amongst musicians who want an all‑in‑one solution.On the back panel are six analogue outputs: the four Main outputs on quarter‑inch jack sockets are capable of being used balanced or unbalanced, and the two Aux outputs are unbalanced on gold‑plated phonos. There are also MIDI In and Out sockets, and the connection for the 25‑way cable to the PCI card.

Installation & Drivers

After I had installed the PCI card in a vacant slot, it was correctly recognised during the reboot, and the Windows 98 drivers were also installed after I inserted the CD‑ROM on request. The only other thing I had to do was install the Control Panel software by running the Setup.exe file on the CD‑ROM. After restarting my PC to let the drivers 'take', I returned to my desktop to find a new icon and menu shortcut for the Direct Pro 24/96 Manager, and just 1.7Mb of new files on my hard drive.

Aardvark also include a copy of the Samplitude Basic digital multitracking studio software from SEK'D. As always, bundled software is a bonus for those who are just starting out, but most musicians who are going to pay for the Direct Pro are likely to want a more sophisticated application.

As I fully expected, ASIO drivers had also been installed, and these appeared in Cubase VST as 'ASIO Aardvark Cards driver'. When selected they gave me a very respectable latency of 12mS. In applications using the standard Windows MME drivers, the new card appears as three stereo input pairs and three stereo output pairs. ASIO 2.0 drivers are expected by the time you read this, and Windows 2000/NT drivers are expected 'in the spring'. There are currently no DirectSound drivers, as this standard only supports 16‑bit audio, but these might be released in the future if there is sufficient demand. None of the Aardvark range has drivers for Macs.

Staying In Control

The Control Panel graphically mimics a small mixing desk and controls features in the DSP engine on the PCI card. The panel is divided into five main areas: input selection and gain trim, input effects (EQ and compression), a 10‑channel monitor mixer, a reverb processor and a set of configuration options.

The Control Panel (here seen in its fetching Gold colour scheme) is certainly versatile, and crams a surprising number of features into its small panel.The Control Panel (here seen in its fetching Gold colour scheme) is certainly versatile, and crams a surprising number of features into its small panel.Each of the four inputs has a comprehensive set of gain adjustments. Rather than using the approach adopted by many low‑cost mixers by optimising the input circuitry either for low‑level mic signals or for line‑level signals, the Direct Pro adjusts the gain at three separate stages in the circuitry in order to cater for a wide range of signal levels. The 'LN' button provides a gain range of between ‑14dB and +9dB, 'MC1' provides between +32dB and +55dB, and 'MC2' provides between +52dB and +75dB — presumably for very low‑level mic signals.

While the Control Panel's first two inputs are hard‑wired to the corresponding physical inputs on the breakout box, inputs three and four can be globally switched to be fed from the stereo S/PDIF In by clicking on their graphic titlebar. In this mode there is a 'signal present' indicator, and gain trim of between ‑12dB and +24dB. This gain adjustment apparently takes place in the digital domain, but if you leave it set to 0dB your DAT transfers should remain unaltered.

Beneath the input‑configuration section of the Control Panel, each of the four input channels has a Compressor. This has rotary controls for Threshold between ‑36dB and 0dB, Ratio between 1.00 and 11.00, Attack between 1mS and 100mS, and Release between 20 and 2000mS. Next in the signal chain is a 3‑band EQ with ±12dB control for each band. The High control is set at 8kHz, the Low at 220Hz, and the Mid can be swept between 50Hz and 15kHz. Both the Compressors and the EQ have two additional buttons: BP bypasses the processor and PS launches a separate window for loading and saving presets. Here you can give a name to the current settings and Add it to the list, select another named preset and Recall its settings, Delete a preset, Change Name of an existing preset, or Change Parameters of the selected preset to the current settings.

Monitoring Your Performance

Below the EQs are the monitor mix controls. These let you mix together the four input signals and the six playback channels available to your audio applications via the three stereo output pairs of the soundcard driver software. Each of the 10 audio channels can have reverb added if required, and the combined output from the monitor mixer can then be patched to any of the analogue outputs or headphone socket.

Monitoring facilities for the four input channels are as follows. At the top is what the manual describes as a Reverb Send control, but which actually sets the balance between 'dry' at 0 percent to fully 'wet' at 100 percent — however, the reverb is normally used only for monitoring purposes, and is not therefore added to the signals being recorded. Below this is a level fader and a peak‑reading meter with 'LED' clip indicator. Two further small readout boxes display the current peak level and the current position of the fader, both in decibels. To the side of the meter are three buttons labelled Rec Fx, Mute and Solo, and at the bottom of each strip is a horizontal slider for Pan, although sadly this has no readout box so you cannot accurately tell where the central position is. Inputs one and three also have a Stereo button which, when active, links the position of their controls to inputs two and four respectively, as well as forcing the Pan controls to hard left and hard right respectively.

I initially found the monitoring section confusing, because some of the controls have different functions depending on the setting of the Rec Fx button. With the Rec Fx button off, the input signal is sent to the hard disk before the EQ and compression, with the peak‑reading meter, clip indicator and current level readout box all displaying this direct signal level. In this mode the channel fader, Mute and Solo buttons, and Pan control only affect the monitored signal, and have no effect at all on the recorded signal. However, when the Rec FX button is lit the signal being recorded to hard disk is taken from after the Compressor, the EQ and the fader, and in this mode is affected by the Mute and Solo buttons — the Reverb and Pan positions, though, still only affect the monitored signal.

The monitor controls for the three stereo playback channels are rather simpler. At the top is the rotary Reverb mix control with current setting displayed in a box alongside, and beneath this are a pair of level faders with text position readout boxes, and associated peak‑reading meters with clip indicators. At the bottom of each stereo playback channel strip are Mute and Solo buttons.

The overall output level of the mixer is set by a pair of faders labelled Monitor. These are longer than those for the stereo playback channels, but otherwise similarly specified. There are two additional buttons beneath these faders labelled Peak and Reset. If the Peak button is activated, a peak hold function is added to every meter in the mixer, and the Clip indicators stay lit if clipping has occurred until the momentary Reset button is clicked.

Reverb & Patchbay

You can save and recall a selection of presets for the EQ, Compressor, Reverb, and the entire panel. You can also see in this screenshot how much clearer the meters and indicators are in this Silver colour scheme, at the expense of the control labels.You can save and recall a selection of presets for the EQ, Compressor, Reverb, and the entire panel. You can also see in this screenshot how much clearer the meters and indicators are in this Silver colour scheme, at the expense of the control labels.The remainder of the mixer is divided into three sections. At the top is a pair of large 'VU' meters that display the output level of the mixer with similar ballistics to a moving‑coil meter. Beneath these are the controls for the Master Reverb. This offers a choice of three different algorithms for room size available from a drop‑down box — Room, Hall, and Church. Along with these are three rotary controls for Decay (100mS to 20 seconds), Diffusion, and Brightness. Both of the latter are arbitrarily labelled from 0 to 100. Finally, as with the EQ and compression blocks, there are two small buttons for Presets and Bypass.

The final strip of four controls under the Master Reverb is labelled Patch Bay, Presets, Advanced, and Source Select. Clicking on the Patch Bay button launches a further graphic window (see screenshot on page 172) which shows the complete range of sources on the left‑hand side, and the range of possible destinations on the right. Clicking on any of the sources creates a 'patch cord' that you can drag across to any destination. Possible sources include the two pairs of analogue inputs (or one pair of analogue inputs and the stereo digital input if this is activated), the three pairs of hard disk playback channels, the combined output from the monitor bus, and two test signals — one is an unusual choice of 1.4kHz sinewave, and the other is digital silence.

There are three possible stereo destinations. The first is 'Analog 1, 2 Out'; signals routed here emerge at the pair of quarter‑inch jack sockets on the back panel of the breakout box labelled Main 1 and 2. The second destination is 'Analog 3, 4 Out' and 'S/PDIF L, R Out'; signals sent here are sent simultaneously to both the rear sockets labelled Main 3 and 4 and the digital phono output on the PCI card backplate. The third is 'Analog 5, 6 Out' and 'Headphone L, R', with signals appearing simultaneously at the rear Aux 5 and 6 phono sockets and the front‑panel headphone socket. Depending on how you choose to work, this doubling up may prove ideal or frustrating.

The Patchbay lets you drag virtual patch cords between its inputs and outputs using the mouse — you can send any input or any output, and even listen to the combined output of the monitor mixer.The Patchbay lets you drag virtual patch cords between its inputs and outputs using the mouse — you can send any input or any output, and even listen to the combined output of the monitor mixer.The generally informative Owner's Manual gives various sample configurations for the Patch Bay and of particular note is the fact that you can monitor the signals at any of the input sockets through any of the outputs with 'zero' latency, whether the compression and EQ are switched in using the Rec Fx button or not.

The Presets button gives you the same facilities as those for the EQ, Compressor, and Reverb sections, but in this case lets you save the current position of every control in the mixer — very handy once you have established several setups to suit your outboard gear and way of working. The Advanced Menu shows the current driver and DSP versions, gives a readout of 'PCI bus Efficiency', and lets you alter the size and bit depth of the ASIO drivers. By default the drivers run at 16‑bit with a buffer size of 256 bytes, giving the latency of 12mS mentioned earlier, but you can increase the size to either 512 or 1024 bytes if your PC suffers glitches at this lowest setting, and increase the bit depth to 24. The final part of this section of the mixer is a text box labelled Source Select, and here you can choose from an Internal clock at 32, 44.1, 48, or 96kHz, or an external one derived from the S/PDIF input.

It's worth noting that all effects are disabled when you are running at 96kHz — this is simply because the DSP engine is already being fully used at 48kHz, and would need double the processing power to keep up at 96kHz. Also, although I had no problems using 96kHz with the MME drivers in Cubase VST and Wavelab, the ASIO drivers refused to be set to 96kHz — an error message appeared every time I tried it.

Multimedia sample rates of 11 and 22kHz are not supported, and nor is 88.2kHz. More worryingly, I also didn't manage bit‑accurate transfers using the S/PDIF I/O, although judging by my measurements the only difference seems to be one bit's worth of dithered noise, which shouldn't worry most people. You do however get the useful options to increase the S/PDIF gain on the way in to compensate for low‑level DAT recordings, and to add some EQ and compression.

There are a couple of useful extra settings on the standard Windows menu bar at the top of the mixer — here you can select which of up to four Direct Pro cards you are currently controlling, and choose one of four colour schemes for the entire mixer — Silver, Gold, Red or Blue. Although the mixer graphics are very attractive, I found myself switching between the colour schemes not for aesthetics, but simply to enhance visibility. On my monitor screen the control legends are far more legible with the Gold setting than with any of the others, but this choice makes the meter displays more difficult to read. In fact, I only discovered their Peak Holding function after reading the manual — I simply hadn't noticed the red 'peak hold' lines in the meters.

In Use

From the moment I listened to the first 16‑bit file being played back in Wavelab I could hear the improvement compared with my own benchmark Echo Gina card — the Direct Pro 24/96 oozed effortless quality and pin‑point stereo imaging. The audio quality is largely down to the converters, but I suspect that Aardvark's improved clock stability has a lot to do with the stereo imaging. As expected, 24‑bit audio sounded even cleaner, although I was rather disappointed with the results of my line‑level RMS background measurements: with 16‑bit files the best figure I could get was ‑91dB RMS, and with 24‑bit/44.1kHz files this only dropped to ‑93dB RMS, and ‑96dB RMS at 24‑bit/96kHz. I would expect results at least 10dB better than this at 24/44.1, so perhaps this was a rogue unit — however, when I reviewed the Terratec EWS88MT (which has identical AKM converters) it also gave higher noise figures than I was expecting.

The mic inputs certainly sounded quiet and clean, and although electric guitarists may initially be disappointed that there is no high‑impedance input, British distributors The UK Office also offer high‑impedance converters at about £20 that plug into the mic inputs. On the monitoring side the EQ certainly sounded musical, even at high boost settings, although with such small controls it is slightly fiddly to set up. The Compressor is also useful in keeping the levels of enthusiastic performers under control, especially when used with the higher ratio settings, although with no gain‑reduction meters you have to rely on your ears alone when setting up.

You can get a surprising variety of useful settings from the reverb, despite its uninspiring interface. With a little effort I managed to create a worthwhile batch of presets for ambience, various bright and dark rooms, halls, churches and cathedrals. All of the reverb tails seemed relatively smooth, but it was fairly easy to get metallic coloration, and while adequate for monitoring purposes it doesn't compete with any quality plug‑ins, so I doubt that many musicians would want to use it on their recordings.

Overall the mixer interface is certainly versatile and attractive, but the meters could do with having higher contrast between their lit and unlit segments, and although both faders of the stereo playback channels move neatly together when either is dragged by the mouse, there seems no way to move them individually for mono signals. The printed User's Manual is fairly comprehensive, but there are some omissions. The Compressor controls aren't covered properly, and many readers will be wondering what driver inputs 5 and 6 are for if there are only four input channels: I had to resort to the 'suck it and see' method to discover that this lets you record the combined output from the monitor mixer, with the DSP reverb if desired.

Final Thoughts

The Direct Pro 24/96 is a clever design, and because its effects are disabled at 96kHz I suspect it is aimed primarily at those who want to record quality audio at 24 bits and 44.1 or 48kHz. Because of its DSP support, it should run quite happily even with a slower processor such as a Pentium 166MHz. The Direct Pro 24/96 should appeal to quite a few musicians who want an all‑in‑one solution to replace an existing small setup of soundcard, mixer, preamps and processors. With only four inputs, it won't suit those recording complete bands, but it should cope with most requirements of a personal studio, such as recording a couple of vocals and guitars simultaneously.

There is currently little competition for a product like this. The Roland UA100 (reviewed in the SOS February 2000) has built‑in effects, but at less than half the price not only is its audio quality far removed from that of the Direct Pro 24/96, but it also uses USB and therefore cannot have low‑latency ASIO drivers. Aardvark seem to have carved out quite a niche for themselves with the Direct Pro 24/96, so if you want to make high‑quality mic recordings using your PC you should definitely take a look at it.

Brief Specifications

  • Analogue inputs: Neutrik combi quarter‑inch jack/XLR connectors.
  • XLR mic inputs: 2kΩ input impedance, balanced, up to 75dB gain, 48V globally switched phantom power.
  • Mic preamps: 8 transistor‑per‑channel discrete mic preamp design.
  • EIN: ‑130dBu (20Hz to 20kHz, 150Ω).
  • TRS jack line inputs: 20kΩ input impedance, +4dBu/‑10dBV, up to 30dB gain trim.
  • Analogue outputs: 4 quarter‑inch TRS connections @ +4dBu/‑10dBV, 2 phono connections @ ‑10dBV, headphone socket @ 32Ω (not more than 600Ω).
  • A‑D converters: 24‑bit 64x oversampling.
  • Input dynamic range: 100dB.
  • D‑A converters: 24‑bit 128x oversampling.
  • Output dynamic range: 110dB.
  • Total harmonic distortion: <0.002 @ 1kHz.
  • Frequency response: 7Hz to 44kHz, ±0.5dB @ 96kHz sample rate.
  • Supported bit‑depths: 16 and 24.
  • Internal DSP engine: 24‑bit, 80 MIPS.
  • Internal sample clock: 32, 44.1, 48, and 96kHz.


  • Excellent audio quality.
  • Zero‑latency EQ, compression, and reverb on analogue inputs.
  • Will work with minimum of Pentium 133MHz processor.
  • Windows 95/98 MME and low‑latency ASIO drivers supplied.
  • Drivers support up to four cards simultaneously.


  • Activating S/PDIF In removes two of the four analogue inputs.
  • Analogue inputs have no high‑impedance option for recording electric guitars.
  • Built‑in effects are disabled when running at 96kHz.
  • No DirectSound, Windows NT or Windows 2000 drivers yet available.


In a single convenient box, the Direct Pro 24/96 provides all you realistically need to record high‑quality acoustic signals.