The 2192 takes an array of versatile digital interfacing, conversion and clocking features, and adds a hint of unexpectedly analogue character...
Universal Audio are something of a double‑edged company. On the one hand, they're well known for their highly respected digital signal-processing plug‑ins, modelled on a wide range of classic analogue hardware. On the other, they're equally well known for their own analogue hardware products, such as the classic UA (and Urei) preamps, compressors and channel strips. There aren't many companies that can stand so proudly in both the digital and analogue camps.
The 2192 Master Digital Audio interface I'm reviewing here isn't new — it's been on the market since 2003, in fact — but somehow it's fallen through our net until now. This device is unique in Universal Audio's product line-up, in that it combines the company's expertise in both digital and analogue technologies to provide a high-performance stereo A‑D and independent D‑A in a 1U rackmount box. The 2192 is styled with a vintage look about it, and operates in a very logical and simple way, while still providing very versatile functionality. Its full name provides a hint as to its intended market.
In many ways, the 2192 is UA's answer to the likes of Apogee's Rosetta 200 (or perhaps more accurately, the previous and now obsolete PSX100) and the Lavry Blue. Like those products, the 2192 provides independent stereo A‑D and D‑A conversion, all within a heavy steel chassis extending about 12.5 inches behind the rack ears, but it also provides digital interface format conversion and can serve as a master clock generator and distributor too. However, unlike most stereo converters on the market, the 2192 uses discrete DC‑coupled, fully balanced Class‑A circuitry throughout, employing matched FETs in low‑gain, discrete op‑amp topologies. As it's DC‑coupled, there are no coupling capacitors and no DC‑servo circuits in the signal path to degrade sound quality or introduce phase distortion.
One advantage of removing coupling capacitors from a circuit is that it allowed UA's designers to lower the circuit impedances significantly, compared to more traditional AC‑coupled designs, and lower circuit impedances bring significant benefits in terms of lowering the background noise floor. This is why the device's A‑D line inputs have the unusually low input impedance of 1.5kΩ — more similar to a mic preamp input impedance than a traditional line input, which would normally be about 10Ω. Fortunately, most modern equipment has very low output impedance (less than 100Ω), so the 1:10 impedance requirement for an effective voltage‑matching interface is still usually met without problems. The results are impressive, though, with the residual converter noise floors comfortably below ‑140dBFS, according to the test plots published in the detailed and helpful 50‑page manual, although perhaps a more meaningful figure is that quoted for dynamic range, which is 118dB (A‑weighted) for the A‑D stage and 122dB (A‑weighted) for the D‑A.
Another interesting design decision is the omission of a dedicated soft‑limit function, to try to prevent unpleasant overloads. Instead, the UA designers have configured the biasing and headroom structure of the analogue input stages so that as the signal nears digital clipping, the circuitry naturally compresses the signal, with a gradual increase in musical 'harmonic bloom.' Universal Audio claim this approach provides useful benefits in terms of the overall sound quality. It certainly gives it a 'vintage' character.
The A‑D portion of the 2192 accepts a line‑level balanced stereo analogue input (0dBFS = +22dBu) via a pair of rear‑panel XLRs. A front‑panel rotary switch labelled 'Digital Outputs', logically enough, determines what is fed from the rear-panel digital outputs — either the signal from the A‑D converter, or that from any of the D‑A section's digital inputs (ADAT, AES3 or S/PDIF) — providing a useful digital interface format conversion facility.
The digital outputs can operate at any standard rate up to 192kHz, although the format‑conversion mode doesn't include sample‑rate conversion (the output sample rate will always be the same as the input sample rate). When it's used as an A‑D converter, the sample rate can be derived from any external clock source or from the internal generator, the rate of which is selected by another front-panel rotary switch offering all six standard rates from 44.1kHz to 192kHz.
Digital outputs are provided in AES3 (via a pair of transformer‑coupled XLRs), S/PDIF (transformer‑coupled phono socket) and ADAT (optical) formats. The ADAT port employs S/MUX data interleaving for sample rates above 48kHz, and the AES3 outputs are duplicated to allow standard 'single‑wire' connection, or legacy dual‑wire interfacing (although I've never found anything that required this format since the mid 1980s!). All three output formats can be used simultaneously. The A‑D's output can also be passed directly to the D‑A section and output as an analogue signal again, if required!
Two separate, nine‑segment, stereo bar‑graph meters are provided to monitor the analogue input and output levels, although they are calibrated to reflect the associated digital signal levels (ie. both are scaled with 0dB at the top).
The unit's sample‑rate clocking can be derived internally, as I mentioned above, or from one of two independent external word-clock inputs (permanently terminated with 75Ω ), or from any of the D‑A's inputs (as already mentioned). The unit also supports ±12.5 percent varispeed sync clocking. Usefully, the 2192 incorporates a four‑output clock‑distribution amplifier, too, and the external‑clock input circuitry supports quarter, half, double and quad multiples of the desired clock rate — so that a 48kHz reference can be used when operating at 96 or 192kHz, and vice versa, for example. Strangely, the old Digidesign x256 Superclock format is not supported at all.
The D‑A's balanced analogue outputs are presented on a pair of XLRs, and the input signal is selected by another front‑panel rotary switch ('Analog Outputs') from one of four options: the output of the A‑D converter, ADAT (with S/MUX decoding), AC‑coupled S/PDIF, and AES3 (transformer‑coupled single‑wire or dual‑wire modes). When working with any of the digital inputs, the source's embedded clock is extracted by a 'unique conditioning circuit' to eliminate interface jitter.
However, the AES3 and S/PDIF inputs share a common decoder circuit, so the required source must be pre‑selected via a front‑panel push button (a second button below switches the AES3 I/O ports between single- and dual-wire modes). This input configuration makes the unit slightly less versatile than might first appear — you can't provide D‑A conversion from an AES3 input while simultaneously format converting an S/PDIF source, for example — but I doubt that will trouble most users.
Although the analogue input and output levels are calibrated at the factory with an alignment of +4dBu = ‑18dBFS (giving a clipping point of +22dBu), there are recessed multi‑turn level trimmers on the rear panel, to allow custom operating levels to be established for both the A‑D and D‑A converters. Full level for the A‑D stage can be adjusted between +5.5 and +30dBu, while the maximum D‑A output level can be trimmed from +23 down to +4dBu.
There are also separate internal trimmers to adjust the output‑meter calibration (factory set for 0dBFS = +22dBu, of course). The manual is very clear and thorough about these calibration procedures, although you will need an appropriate signal generator and measuring test equipment to do the job properly. Eight internal jumper links are provided to break the connection between chassis ground and pin 1 for each analogue and digital XLR connector, making it easy to provide ground lifts if necessary.
The internal mains power supply is a universal type accepting any mains voltage source between 100 and 240V AC via an IEC socket. Power consumption is a modest 40W. The rear-panel connectors are all well laid out for easy access and clearly labelled, while the front panel is delightfully simple, despite the unit's considerable flexibility, and has a lovely retro style about it. All the switches and controls feel solid and reliable, with positive actions that convey the impression of a serious, high-quality, professional piece of kit.
Like many high‑end converters — especially those with discrete analogue I/O stages — the 2192 takes a while to warm up before it delivers the sonic quality it's capable of. The character changes quite substantially during the first 15‑20 minutes, so don't be tempted to just switch on and go. Actually, you can't just switch on and go anyway because the unit goes through various self‑test routines at power up. It takes a couple of seconds for the PSU module to decide it wants to play and illuminate the blue power light, and then another 10 seconds or so before the sample‑clock light comes on to indicate that the digital circuits are all up and running.
And 'warm up' is the appropriate phrase! The 2192 actually runs surprisingly warm, so ensuring that the air can flow unimpeded through the various ventilation holes is important. Don't crowd this unit in a rack: I'd suggest leaving a 1U space above and below if you can. Perhaps not surprisingly, the unit also generated some scarily loud glitches occasionally when changing operating modes, so it would be wise to mute or at least turn down the monitoring before reconfiguring anything.
Connecting and configuring the 2192 is very straightforward, thanks to the clear socket labelling and extremely logical front‑panel switches. I hooked the unit up in place of my old Apogee PSX100 which I use for general-purpose monitoring and linking various legacy recording equipment, and while it's not quite as versatile as the Apogee, the considerably easier user interface was a joy. The most significant operational difference between these two units, and one that caused particular issues in my setup, is the fact that the 2192 operates at 24‑bit resolution all the time. There's no provision for word‑length reduction and dithering to 16 bits to work with legacy recording formats like CD-R or DAT. Thankfully, though, most modern standalone CD‑R machines have this facility built in anyway — and who uses DAT anymore?
The Apogee couldn't really be described as a truly transparent or completely neutral converter, especially when compared with more modern units, but it's not at all bad, and the very mild coloration it imposes is entirely benign. In comparison, the 2192 sounds distinctly 'analogue' with a much fuller character overall. It's noticeably richer at the bottom end and slightly more forward through the upper-mid range — vocals tended to have a tad more presence and clarity, for example, in my tests. Like all high-end equipment, these characteristics are subtle on their own, but become plainly audible in direct comparisons with other equipment. Comparing the 2192's D‑A section with my reference Benchmark DAC1 and Grace Design M902 units, for example, it comes across in the same way: fuller, richer, more analogue — and most enjoyable to listen to. It has a distinct character, but a very pleasant one that I'm sure would suit anyone who feels digital recording is still too clinical. However, there is also excellent resolution here — low‑level details and ambiences are handled beautifully, and the high end is open and airy at all sample-rate settings.
On the A‑D side, the character becomes progressively enriched as levels are pushed harder towards 0dBFS, and transient compression becomes more obvious too. It's obvious just from listening that clipping is approaching — just as with much analogue equipment. However, working with normal tracking headroom margins of 10dB or so results in a comfortably linear and natural dynamic response. Again, detail resolution is excellent and background ambiences are handled smoothly, with a very quiet and stable noise floor.
All the I/O worked as intended during my tests (bearing in mind the fixed 24‑bit word length), and the inclusion of clock distribution facilities would prove very handy in some digital studio and machine‑room setups.
The 'Master Digital Audio Interface' label hints at the role UA intend for this unit, and where a straight stereo A‑D/D‑A interface is required, the 2192 gets the job done very nicely indeed. It provides some 'olde worlde' musical character, which many will welcome, while also performing a range of I/O functions and conversions with very high-quality professional results. I was very impressed with the ease of use and sonic quality of the 2192. It might not appeal to ultimate purists, but for those who prefer a more musical, characterful experience, this unit ticks all the boxes.
The market for stand-alone stereo converters has diminished somewhat with the increasing dominance of Firewire and USB-based audio interfaces, but there's still some serious competition around. The 2192 Master stands comparison with devices such as Apogee's Rosetta 200, the Lavry Blue and Burl's separate B2 Bomber DAC and ADC units. The Prism Sound Orpheus is a superb contender offering rather more functionality. If you want a less coloured sound, there are more affordable units available from the likes of Drawmer, Benchmark and RME.
The 2192 is built to high standards, with an unusually heavy steel lid to the robust rackmount case. The internal power supply is an OEM switched‑mode design from PowDec, shielded from the rest of the electronics by steel screening 'walls'. It makes sense to use a third‑party power supply module like this because of the effort and expense involved in getting all the relevant CE, TUV and UL safety approvals for a bespoke design.
The majority of the electronics (almost all surface-mount components) are arranged on a single large motherboard covering most of the available real-estate inside the box. Another steel dividing wall separates the front-panel controls and associated 'daughter' circuit cards from the main board, with a few ribbon cables linking everything together. The analogue audio input and output stages are surprisingly elaborate and built using standard FET components on a set of six small circuit cards, supported on raised studs above the motherboard.
The stereo A‑D converter chip is an AKM AK5394 delta‑sigma converter operating at 128x the sample frequency, with differential inputs for each channel and intended specifically for professional high-quality audio applications. The D‑A converter chip is another AKM device, this time the AK4396, which is intended primarily for DVD‑Audio and SACD applications. Again, it is a 128x delta‑sigma design with differential outputs. It is the availability of these differential inputs and outputs that has enabled Universal Audio's designers to avoid coupling capacitors in the analogue I/O circuitry.