ST Audio DSP3000 M-Port

Photo: Mark Ewing

ST Audio's DSP3000 system offers an impressive feature set for its price, boasting eight-channel 24-bit/96kHz analogue I/O with mic preamps on every channel, plus digital I/O in S/PDIF and AES-EBU formats, MIDI I/O, and the ability to function as a stand-alone analogue/ADAT digital converter.

Although ST Audio (aka Korean-based company Hoontech) have plenty of budget offerings in their range, there's nothing entry-level about the DSP3000 M-Port under review here. It comprises a DSP24 PCI card, its associated XG DB1 daughter card with S/PDIF and AES-EBU digital I/O, and a 2U high rackmount case labelled 'ADC&DAC 3000', which houses the various converters and audio electronics. In here you'll find eight balanced microphone preamps with phantom power and insert points, dedicated LED ladder-array level meters for each channel, ADAT and word clock I/O, and one MIDI In and two MIDI Outs.

This is an impressive array of features, and the ADC&DAC 3000 is also available as a stand-alone unit for those who already have an ADAT-compatible device like a digital mixer or multitrack recorder. The DSP24 PCI expansion card is also available separately, and can be partnered with a variety of other ST Audio I/O options, including the analogue-only ADC III and DAC III, the ADC&DAC 2000 with eight unbalanced ins and outs plus two mic preamps, the multi-channel S/PDIF I/O of the DM III, and the ADAT and TDIF options of the DS2000. Drivers are available for Windows 9x, Me, 2000 and XP, and although it was not mentioned on the packaging, I subsequently discovered on the ST Audio web site that Max OS X drivers are now also available.

Overview

Photo: Mark EwingAlthough it looks very similar, the DSP24 PCI expansion card differs from the one used in the DSP24 Media 7.1 we reviewed in SOS January 2003. Both feature a trio of 3.5mm sockets for the Mic In, Line In and Line Out of the internal AC97 sound chip intended for Windows system sounds, plus a D-type connector for the external converter box, along with headers labelled CD In and Aux In for attaching internal devices such as an analogue CD-ROM output (a suitable cable is supplied for such duties).

The DSP3000's digital I/O is provided on a daughter card. Photo: Mark EwingHowever, where the Media 7.1 digital I/O is all to be found in its external breakout box, the DSP24 S/PDIF I/O is all situated on a daughterboard and backplate that connects to the main DSP24 card, so it has an extra four-pin connector and associated internal cable to connect the two, plus another two-pin connector to suit a digital output from a CD-ROM drive (you can choose either S/PDIF or CD digital in, but not both). This is because the two cards are supplied as a pair with other analogue-only I/O options, and means that you'll need two spare expansion card positions, but this shouldn't prove a problem in most cases. Usefully, the S/PDIF I/O is available in both Toslink optical and phono co-axial formats, and also as two 3.5mm jack sockets labeled AES-EBU, which will require appropriate XLR adaptor cables to interface with other AES-capable equipment.

The ADC&DAC 3000 adopts the same livery as the Media 7.1, with a blue-splatter paint finish and smart metallic blue milled aluminium front panel. All I/O sockets apart from the headphone output are on the rear panel, and comprise balanced XLRs for the eight mic inputs and channel outputs, unbalanced quarter-inch jacks for line inputs, and TRS-wired quarter-inch Insert jacks. One thing to bear in mind here is that since the mic inputs are 'round the back', you might consider routing them permanently to a suitable patchbay for easy access once bolted into a rack. However, when you plug anything into a line-level input, the corresponding XLR input is deactivated, which means you can't leave both permanently connected and switch between them.

Each of the inputs has its own rotary gain control, plus an optional +48 Volt phantom power switch and 'active' LED per input pair. Next to the input controls are eight calibrated 10-segment LED meters to monitor either input or output levels for each of the eight channels via eight latching buttons beneath. The front panel is completed by a headphone output and level control, 44.1/48kHz sample-rate selection for stand-alone use via the ADAT I/O, and a power switch and associated LED. I did find the latter rather annoying, since it illuminates red on standby, and switches to yellow when you flick the switch to the On position — it's easy to forget which colour is which, and you are supposed to have the rack unit switched on before you boot your computer, and reboot it after any change.

The rear panel is completed by the 12 Volt DC input to plug in the supplied line-lump PSU, which will run at a pretty universal 100 to 240 Volts AC at 50Hz to 60Hz, plus ADAT in and out, word clock in and out, and Data In and Out — the latter are to connect the DSP24 card and the optional external expansion boxes mentioned earlier. The ADAT I/O is primarily intended for stand-alone converter use, with the eight analogue inputs hard-wired to the ADAT output, and the ADAT input hard-wired to the eight analogue outputs — not as versatile as some might like, but still a useful function, and an added bonus compared to many units in this sector of the market.

The ADC&DAC 3000 rackmount unit has eight line inputs and eight mic inputs, all on the back panel, and connecting anything to a line input disables the corresponding mic input.Photo: Mark Ewing

The AKM AK4393 D-A converters are identical to those used in M-Audio's Delta 1010 and Echo Mona among others, while the A-D converters are CS5396 chips from Crystal. Both boast a 120dBA dynamic range at chip level, although real-world figures with the output buffer and input preamp circuitry will be significantly lower.

Drivers & Utilities

The DSP24 drivers appear to Windows as a total of seven stereo input and seven output devices.Photo: Mark EwingThe drivers support up to four DSP24 cards, each providing up to 10 inputs and outputs, while the ADC&DAC 3000 also has a set of 10 DIP switches in a small recess on its right-hand side as viewed from the front. These let you give up to four devices their own unique ID number for software control from the supplied utility, so it's possible to assemble a monster 40-in/40-out channel system if you wish.

The latest Windows XP drivers on the ST Audio web site were version 7.2.1014, dated October 2002, so these were the ones I installed. The reason for this 'maturity' is that the same drivers are used for the DSP24 (and its MK II and System III versions), the DSP2000 and the latest DSP3000 release. The bundled software seems to be identical to that supplied the DSP24 Media 7.1, comprising a special version of Emagic's Logic named Soundtrack 24 v4.2 with 24-bit/96kHz capability that runs on Windows 9x, ME, 2000 and XP, plus a variety of other freeware, demo, and trial versions of other music software.

To Windows the DSP24 drivers appear as a total of seven input and seven output devices — the four analogue output pairs, the S/PDIF I/O, the Internal AC97 Codec, and the DSP Mixer. I did experience an odd anomaly while installing the XP drivers: both my BIOS and Windows detected the new DSP24 card, but after I pointed Windows to the appropriate drivers, it claimed it couldn't find any that suited the hardware. However, after I powered down the computer and re-seated the card in its slot, Windows was more forthcoming on the next boot, and I was up and running.

The settings on the External Links page determine how the hardware inputs are connected to the PCI card's input ports, and what's connected to the physical DAC outputs. Here's a good default setup that also displays DAC output pair 7/8 directly connected to input pair 7/8 to establish 'zero'-latency monitoring. Photo: Mark EwingWell, at least I thought I was. After successfully playing back some recordings through the Wave Outs, I ran into problems trying to use the inputs: although the hardware input meters showed that signals were present, nothing was audible from the computer end. Of course I should have read the User's Guide, since this explains in great detail that you first have to perform a one-off configuration using the Add Inputs option on the External Links page of ST Audio's Control Panel software utility, to tell the DSP24 driver what hardware options are connected.

In my case this was a single ADC&DAC 3000 and an XG DB I for the daughterboard S/PDIF I/O, and once I'd selected these, their graphic images appeared in the External Links page. You can then connect 'patch cords' from the various physical analogue and MIDI inputs to appropriate ports on the PCI card (see screen shot), whereupon the LEDs above the relevant channel pairs on the rack unit illuminate to show that they are 'active'.

Although I found this confusing at first, it does enable users to configure up to four PCI cards and multiple I/O boxes as they wish. Thankfully the DSP24 hardware automatically recognises all available outputs. The External Links page also lets you set up the 'zero'-latency monitoring, by connecting the physical DAC outputs to the various input pairs instead of the Wave Out (playback) connections.

The External Mixer page lets you set up a mix of the various input and output signals that can then be routed to either DAC outputs 1/2, the S/PDIF outputs, or both. Photo: Mark EwingThe External Mixer page is very similar to that of the Media 7.1, with input channels for each input and output signal, complete with pre-fader metering, Mute and Solo buttons, pan controls, and an output fader. The mixed output signal passes to a pair of Master channels with their own meters, faders, and global Mute button. Back on the External Links page, the output from this External Mixer can be routed to the S/PDIF output, analogue 1/2 outputs, or both for monitoring purposes, and four mixer presets can be loaded and saved, which is handy for setting up input monitor mixes for headphone feeds or combining the outputs from various analogue channels into one physical output.

This latter option is particularly useful in conjunction with the third and final page of this utility, Hardware Settings, since here you can assign a different driver format to each output pair (Wave Out 1/2, 3/4, 5/6, 7/8, and S/PDIF Out), from a choice of MME, ASIO or GSIF. This flexibility is very welcome — as I use both Cubase and Gigastudio, I would allocate 1/2 and 3/4 to ASIO duties, 5/6 to MME for Wavelab, and 7/8 to GSIF for Gigastudio.

Also on the H/W Settings page are Internal/External clock options, sample-rate locking, Multi-channel Device Support for MME applications such as DVD surround players, and buffer size selection for the MME/ASIO drivers, which has options down to an extremely low 64 samples. This would offer a latency of 1.5ms at 44.1kHz, and 0.7ms at 96kHz, although such values are normally impractical due to high CPU overhead.

Audio Performance

Within a couple of minutes of initial WAV playback auditioning, my ears were telling me that something was wrong at the bass end. Sure enough, once I got Rightmark's Audio Analyser 5.0 loopback connection established, the measured high-frequency response was fine (only 0.5dB down at about 44kHz when using a 96kHz sample rate), but low frequencies were seriously lacking, being 0.5dB down at 120Hz, and -3dB at 45Hz. I repeated my measurements using various other combinations of inputs and outputs, but the results were essentially the same.

The review sample had an extended high-frequency response that was only 0.5dB down at about 44kHz when using a 96kHz sample rate, but had significant bass roll-off, resulting in a response that was 3dB down at 45Hz. This has now been resolved at the factory (see main text). Photo: Mark EwingI had encountered a similar problem when reviewing ST Audio's DSP24 Media 7.1 a few months back, this time with the high-frequency response, so this points to poor checking of production-line samples. ST Audio soon confirmed my findings, and reported that the problem was again simply due to unsuitable capacitor values being used, and was easily corrected. From serial number HOON0315 onwards more suitable values will be used, and all remaining units in the field will be recalled. Reassuringly, UK distributors Et Cetera have also promised me that anyone who has already purchased a DSP3000 can contact them to have it collected free of charge and replaced with an updated model.

While talking to ST Audio, I also complained at the lack of detail in the published audio specification of the DSP3000 — not only are there no frequency response or distortion figures quoted in the User's Guide, or on the web site, but the various DSP3000 input sensitivities and output levels are also missing. While this could possibly be overlooked in a budget soundcard, the DSP3000 retails at nearly £700, and potential users of a 10-in/10-out device will need to know whether or not it can be interfaced to their existing gear. This also turned out to be an oversight, and the full technical spec will be on the Et Cetera and ST Audio web sites long before you read this.

I'm pleased that these points have been resolved, since otherwise the DSP3000 is a fine performer. Barring the lack of low-frequency extension, playback sounded very good, with plenty of focus and transient detail. Recordings made through the line and mic inputs were quiet and clean, and background noise levels measured -93dB at 16-bit/44.1kHz, an excellent -110dB RMS at 24-bit/44.1kHz, and -105dB RMS at the wider bandwidth of 24-bit/96kHz.

With my standard raft of latency tests I found that Cubase SX could run glitch-free with the DSP24 ASIO drivers down to a good 3ms latency using the 128-sample buffer setting, running alongside Gigastudio 160 with the GSIF drivers. Sonar 2 also performed well down to 3ms, although CPU overhead was rising noticeably by this point. Pro 53 also managed a 3ms ASIO setting in stand-alone mode, and was quite happy with the DSP24 Direct Sound drivers operating at 20ms latency, but as with many other audio devices under Windows XP, the MME drivers provided a less impressive glitch-free latency of 50ms. The mix-and-match driver format options worked very well, and overall I found the DSP3000 a good performer.

In The Balance

With eight mic preamps, the DSP3000 should prove ideal for anyone who wants an all-in-one solution for recording a small ensemble. While there are plenty of competing products offering eight ins and outs plus digital I/O, nearly all provide line-level inputs only, while those that do offer mic inputs normally restrict them to just a few channels. The only real competition for the DSP3000 that I can think of is the Aardvark Q10, now available two years after its release at street prices of about £730. This does have a couple of additional guitar preamps as switched options on inputs 7/8, and a more compact 1U rackmount case that still manages to have its mic inputs on the front panel for easy access.

However, the Q10 has inserts only on its first four inputs, no input gain controls, and only co-axial S/PDIF I/O, whereas the DSP3000 offers co-axial, Toslink optical, and AES-EBU digital I/O options, plus basic ADAT I/O, full front-panel metering, and considerably lower background noise levels for about £100 less at street prices. It's always disappointing when a product comes in for review with a fundamental problem that should have been spotted at the factory, but thankfully in this case it was easily solved, and shouldn't affect the units that are in the shops now. With this in mind, the DSP3000 gets a cautious thumbs up for its versatile combination of features at an excellent price.