3 Stand-alone D-A Converters Compared

If your music relies on soft synths and samples, playback quality is more important to you than your recording chain, so adding a high-quality, stand-alone D-A converter may be the most targeted way to improve your system.

In studios that range from tiny bedroom setups to commercial enterprises, improving the existing audio quality is a popular topic, and there are regular requests on the SOS Forums for advice about buying a high‑quality clock generator to improve the sound quality of existing A‑D and D‑A converters. The aim is to lower the converters' clock jitter level — that is to say, the amount of timing uncertainty in digital audio's low‑to‑high and then high‑to‑low transitions (analogous to 'camera shake').

Most 'master clock generators' offer multiple outputs across various digital formats, and are therefore ideal when working with video, or if you have a complex digital audio setup with lots of gear that requires synchronising to a common clock signal. But to improve the sound of most multi‑channel audio interfaces with a retail price of, say, £800$1300 or less, it will probably be more cost‑effective to sell the existing interface and buy one with equivalent features but better converters and its own higher-quality internal clock. In fact, some cheaper audio interfaces may not benefit at all when fed from even the best external clock signal (more on this later).

Who Will Benefit From A New D‑A Converter?

The two most critical points as far as jitter is concerned are, firstly, when analogue signals are converted to digital by the A‑D conversion process during recordings — where any digital 'shaking' will result in a permanently 'blurred' recording that can't be corrected or improved later on; and, secondly, when digital audio is later converted back to analogue so that we can hear it through loudspeakers or headphones — where any further digital 'shakiness' will blur existing recordings.

Those with compact setups who want to improve their audio recording quality should therefore either investigate a better audio interface, or (assuming their existing interface has some spare digital inputs), buy a box containing a set of more up‑market A‑D converters that incorporate their own higher-quality clock. They can always upgrade their D‑A converters later on to hear further playback benefits when funds permit.

However, for those who primarily work with pre‑recorded material, and particularly for the vast majority who work in stereo rather than surround, devoting a similar amount of money to just two channels of D‑A conversion may provide a more cost‑effective route to sonic nirvana. All you need to do is connect the digital output of your existing audio interface to a standalone D‑A converter with built‑in jitter suppression. Some models even offer USB or Firewire ports that you connect directly to your computer, which means that you require no separate audio interface at all. You should instantly hear all the little musical details that were previously buried under a layer of digital 'grunge'.

This approach should benefit anyone for whom playback is more important than recording, including mixing and mastering engineers, plus all those whose music largely relies on software synths (whose signals are generated inside the computer), sample libraries and software samplers, as well as those who simply want to improve their CD listening experience. Bear in mind, though, that this is just one aspect of the monitoring chain that can be improved (see the 'Audio Upgrades: Which Comes First?' box).

Versatile Performers

The Apogee Mini‑DAC is small, and as it is capable of running on batteries it is an excellent choice for location work.

Improving playback quality is the main reason to consider buying a stand-alone D‑A converter, but many such boxes can be used for other duties too, meaning that they offer better value for money than it might at first appear. Besides offering precision reference monitoring in the studio, most are portable and compact enough to be very useful for location monitoring, especially since most also offer integral high‑quality headphone amplifiers. Once you move beyond the 'cheap and cheerful' headphone distribution amps designed for several musicians to monitor their performances in the studio, higher quality headphone amps can prove surprisingly expensive!

Stand-alone D‑A converter boxes also invariably offer digital input switching options, a precision output‑level control, and sometimes several analogue outputs, so that they can also be used as simple monitor controllers. Plenty of musicians are now looking for such functions when connecting a basic audio interface to active monitor speakers, and unless you require talkback and more comprehensive routing options, the units discussed in this article may give you all the control you need. Finally, for many people, plugging an up-market D‑A box into their CD transport converts it into the ultimate CD audiophile listening station.

For anyone considering such an upgrade, the best approach, if possible, would be to short-list several stand-alone D‑A converter boxes, borrow them all for a few weeks so that you can get to know all their contrasting features; then compare them all with the audio quality offered by a selection of audio interfaces ranging from budget to expensive... and finally make an informed decision after establishing their relative merits. Of course, in practice that won't be possible for many of you, but don't worry, because that's exactly what I've done on your behalf!

The Contenders

There are now some very acceptable consumer soundcards that offer respectable audio quality, but these are invariably bettered by entry‑level products specifically intended for the musician, such as (for example) Emu's 1212M, ESI's Julia, and M-Audio's Audiophile 192; all of which offer audio quality that would have been unheard of for the price several years ago. Superior to these are more expensive products, such as Echo's Audiofire range, the Focusrite Saffire series, and many other interfaces from companies such as M-Audio, MOTU, Presonus and TC Electronic. All of these have huge numbers of fans, but two ranges seem to be particularly popular with musicians: RME's Firewire‑based Fireface 400 and 800, and Lynx Studio Technology's PCI soundcard models, the latter, in particular, being widely considered as the best PCI(e) models available.

When considering a dedicated stereo D-A converter, we should therefore be looking for products that match or surpass the best of the aforementioned devices, but there aren't actually that many two‑channel units on offer. If you need both A‑D and D‑A converters in one box, RME's ADI2 (priced at around £450$800) is highly regarded, and should outclass many audio interfaces. The new DACS Headmaster looks interesting, and there are also various superb high‑end D‑A converters, such as the Lavry Gold DA924, Prism DA2 and Weiss DAC1 Mk2, but these retail at well over £3000$5000 each and are aimed at those who demand the very finest audio quality available.

Over the last few years, though, several D‑A converter units have appeared offering performance comparable with units only available for well over £1000$1600. All of them should offer a significant upgrade in sound quality to nearly all the interfaces mentioned above. I short-listed three respected, comparatively priced, mid‑range stereo D‑A converter boxes whose specifications differ in quite a few ways. On the 'street', Apogee's Mini‑DAC costs about £580$800, while the Benchmark DAC1 and Lavry DA10 Black can be found for around £680$975.

The Mini‑DAC has been around since 2003 and has the distinctive Apogee 'house look', with a very robust silver metal casing and purple metallic rotary knobs. At one‑third of a rack width, its front panel is extremely compact, which is great if you're pushed for space or need to rackmount up to three units side by side. Its external line‑lump power supply won't go down well with some, but it employs very sophisticated high‑speed switching power‑supply circuitry internally that accepts any 6-14V DC source, making it not only very portable but also capable of running on batteries.

Benchmark's DAC1 has been gaining an enviable reputation for audio quality since it first appeared in 2004, and it is now available in both half‑width rackmount and desktop (no rack‑ears) formats, in either black or silver livery, with an attractive sculpted‑aluminium front-panel, and a knurled-metal rotary with detents. Although featuring an internal mains PSU, it sadly doesn't have a front‑panel power switch like the Apogee and Lavry units, which could be annoying to some people — although, as Hugh Robjohns reported in his SOS review, the DAC1 requires at least an hour to warm up from switch-on before it sounds its best, so I suspect its designers intend you to leave it permanently switched on.

The Lavry DA10 Black is the most recent design of the three, and has quickly earned itself a reputation for being a no‑nonsense design that concentrates on high audio quality. Like the Benchmark model, its case is half-rack width, and it's the least distinctive-looking of the three units. It does, however, have a two‑digit numerical display for its digitally controlled (up/down) analogue volume control, which makes achieving repeatable levels much easier — although I wonder if a rotary encoder would have been a more elegant solution. Like the DAC1, the Lavry features an internal mains PSU but it also has a convenient front‑panel power switch.

I/O Differences

The Benchmark DAC1 USB connects directly to your computer, and can be used without a separate audio interface.

The three units differ in their I/O capabilities. On the digital input side, all offer front‑panel switching between AES/EBU, Toslink optical, and phono coaxial options, but the Apogee Mini‑DAC also lets you audition any stereo pair from an eight‑channel ADAT stream, and can be upgraded with an optional Firewire card, which means you won't need an audio interface. Similarly, the Benchmark DAC1 is also available in a USB version that provides a similar direct connection to your computer.

All three provide a pair of balanced XLR main analogue outputs, but the Apogee and Benchmark models both offer a second, unbalanced output option too, allowing you to connect a second device (via a 3.5mm jack in the case of the Apogee, and twin phono sockets for the Benchmark).

While all these products offer front‑panel headphone output sockets (there are two in the case of the Benchmark DAC1), whose level is controlled by the main level controls, the Apogee provides a handy front‑panel switch that can optionally mute the main (normally loudspeaker) outputs, which leaves the headphone and 3.5mm jack outputs intact. There's also a further internal jumper to switch the 3.5mm outputs between fixed and variable level, the latter being controlled by the front-panel level control. The Benchmark DAC1, on the other hand, offers rear‑panel switching, allowing you to set its two stereo analogue outputs to be controlled by the front‑panel rotary control, or be unaffected by it (leaving it for headphone duties), but instead set to your choice of fixed level determined by a 10‑turn rear‑panel trimmer pot.

Although the Lavry DA10 does offer internal jumpers for balanced or unbalanced configuration, there's no way to mute the main outputs while continuing to listen to the headphone output, which could prove to be an annoying omission for some users. In its favour, though, it offers handy front‑panel switches for mono/stereo and normal/invert polarity that the other two don't.

Getting The Jitters

Each of these units can operate over a wide range of sample rates, covering all the standard frequencies from 44.1 to 192 kHz, but the methods employed vary significantly. When you select 'External Clock' in a cheap and cheerful digital audio interface, the internal clock's oscillator is simply disconnected, and the converters blindly follow the incoming clock frequency, complete with any jitter from the external clock, plus any more that's picked up en route via cables, power‑supply noise, and so on — so you could end up with more jitter than you started with!

A better approach is to employ a low‑jitter internal clock, which is physically situated very close to the DAC (to minimise the added jitter of cabling), and whose frequency can be tweaked. You then force this internal clock to follow the incoming clock frequency. Typically, PLL (Phase Locked Loop) circuitry is used for this function. This generates an error‑correction signal in response to any frequency difference between the internal and external clocks, and uses this to correct the internal one, but the error signal is low‑pass filtered, leaving it fast enough to follow any longer‑term changes in the incoming clock rate, but slow enough to exclude jitter noise. Effectively, the D‑A converter is running on its own internal clock, but the PLL is used to synchronise this to the external clock.

Apogee, as do various other digital audio manufacturers, take this approach further in the MiniDAC by employing a dual-stage clock (essentially the same one that's used in its more expensive stablemates). The first is optimised to track timing variations in the incoming data and store it in a digital buffer, whereas the second further attenuates jitter, as described above.

The Benchmark DAC1 has a rather different design, and uses technology the company have named 'Ultralock'. This uses a very high‑quality, asynchronous sample‑rate converter that oversamples the incoming data (at any sample rate from 32 to 192 kHz) by a huge factor, and then down‑samples it again to an unusual fixed sample-rate of 110kHz, clocked out by an extremely stable, internal crystal oscillator. This, of course, means that the emerging data has been re‑computed rather than being 'bit transparent', and also that at sample rates higher than 100kHz data is actually discarded, but Benchmark claim that even 192kHz audio sounds better through the DAC1.

The Lavry DA10 offers three clocking modes: Wide, Narrow and Crystal. Wide is intended for non‑standard sample rates, and where they may vary significantly, and it will lock to any sample rate between 30 and 200 kHz, using a sample‑rate converter similar to that of the Benchmark DAC1. The Narrow option uses a more traditional two‑stage PLL design like Apogee's, with an initial coarse lock followed by a very fine one, and provides bit‑transparency, which makes it the most suitable option if you need to run multiple units in parallel (for use in a surround setup, for instance).

However, it's the Crystal mode that will appeal to the biggest proportion of stereo listeners, since this results in the lowest jitter levels. It's an elegant design, whose error-control signal is itself a 12‑bit D‑A converter with 4096 steps. Incoming audio data is stored in a buffer and clocked out by an extremely low‑jitter internal clock, whose frequency is only updated about once every 10 seconds. Each update either increases or lowers the control DAC value by just one step, and this control signal is then filtered to smooth out the tiny steps and remove any remaining interference. The DA10 only supports rates up to 96kHz in the Narrow and Crystal modes — but then designer Dan Lavry doesn't believe that 192kHz sample rates offer any benefit over 96kHz, and there are arguments to support him in this view.

Jitter Immunity

Lavry's DA10 Black may not offer all the functionality of its competitors — but it provides excellent sound quality.

I was lucky enough to have a Lynx Two soundcard available during my auditions to see how it compared with the three stand‑alone D‑A converter boxes I was auditioning, and to use its high‑quality AES/EBU digital outputs to compare with the S/PDIF outputs of several budget PCI soundcards, to see whether the D/A jitter-reduction circuitry really did make them immune to incoming clock jitter.

I tested the three stand‑alone converters in turn by connecting their AES/EBU digital inputs to the AES/EBU digital output of the Lynx Two (which I already knew to be of excellent quality) and simultaneously connecting their S/PDIF digital inputs to the S/PDIF outputs of my budget Echo Mia and Echo 1820M soundcards. I then switched between these two digital input options using the front-panel switches on the standalone converters. I couldn't detect any difference in audio quality with any combination, so we can conclude that you could feed any of these converters from the S/PDIF output of a modest soundcard and still experience their full benefits.

Audio Performance

I settled down to some serious comparative auditioning of the analogue audio outputs of the Emu 1820M, Lynx Two, Apogee Mini-DAC, Benchmark DAC1, and Lavry DA10 — all of which were connected singly and directly to my power amp, or in pairs via SM Pro Audio's M‑Patch 2 passive monitor controller.

In my previous tests of mid‑priced audio interface quality, Emu's 1820M managed to retain its crown for best audio quality for two years, and it still sounds very good for the price. However, Apogee's Mini-DAC provided a soundstage that was significantly wider and deeper, letting me hear a lot further into the depths of the mix, as well as benefiting from more natural delivery of acoustic instruments, and, in particular, vocals. The mid‑range was also warm and clear, while its bass end was more controlled, and its headphone amp provided a clean and detailed sound, with plenty of power on tap.

To my ears it was a closer call between the Lynx Two and the Apogee Mini-DAC. I liked the clarity and precision of the Mini-DAC, but to my ears the Lynx Two just had the edge, with a more spacious and airy soundstage. However, we're comparing apples and oranges here — even the stereo version of the Lynx Two (the L22) costs around £600$675 on the street, and although it does provide both A‑D and D‑A, there are no monitor or headphone functions. At its current street price of £580$800, Apogee's MiniDAC is a serious contender for anyone who wants a high‑performance and supremely versatile D‑A converter along with a great headphone amp and basic monitor controller functions.

Moving on to the Benchmark DAC1, I can now see why Hugh Robjohns described its performance as "quite extraordinary for the price". While the Apogee MiniDAC had a pleasing up‑front crispness, the Benchmark DAC1 let me hear slightly further into reverb tails, offered even more natural vocal timbre, and once again a wider soundstage (notice a trend here yet?), in which I could more clearly hear where each instrument was placed, while the top end provided plenty of 'air'. Overall, I'd describe the Benchmark DAC1 as having an extremely detailed, focused sound (the same applies to its headphone amp) and for me it had the edge over both the Lynx Two and MiniDAC — although I must stress that these are subtle differences.

Despite the inconvenience of its up/down level‑control switch compared with the rotary knobs of the others, the sound of the Lavry DA10 in Crystal mode proved to be something of a revelation. Compared with the Benchmark DAC1 the soundstage was even wider, but this time it also opened up more front‑to‑back. Overall, it offered a more open and effortless sound, and I found its mid‑range and highs particularly natural, making the DAC1 sound a tiny bit nasal on some vocals (although it's worth pointing out that I'd never have noticed such subtle differences without conducting a direct comparison of the two). These improvements were also audible on the headphone output and, overall, to be able to buy a converter of this quality at this price is something I find amazing.

Final Thoughts

Each make and model of converter has its own sonic signature, and there will always be an element of personal preference involved, so if you're considering such a purchase, you should really make the effort to find a dealer who can demo your short-listed items side by side; or if possible, arrange a short‑term loan for an audition in your own studio.

Nevertheless, any of the three D-A converters reviewed here should provide significant audio improvements over those found in the majority of multi‑channel audio interfaces that you can get for £1000$1800, and in some cases the difference may be breathtaking, if the rest of your signal chain is up to scratch.

You'll no doubt get superior audio results from the more expensive D‑A converters, but the law of diminishing returns applies, meaning that you have to pay significantly more to get even a small improvement at this end of the market — and unless the rest of your signal chain is of exemplary quality, the differences may be extremely subtle.

The Apogee MiniDAC is the most versatile of the three contenders here, provides excellent audio quality, and will particularly appeal to those involved in location recording, where its small size, ADAT compatibility, and battery‑powered option score highly. The Benchmark DAC1 offers superb audio quality for the price, plus twin headphone sockets and the option of main output muting. Both offer two sets of analogue outputs and full jitter‑reduction up to 192kHz, and the Firewire/USB options may be useful.

However, I'd recommend that those for whom audio quality is the most important consideration should audition the Lavry DA10 Black. Despite the frustrating lack of main output mute switch, a fiddly up/down switch for level control, and a single analogue output compared with the two of the others — and Narrow/Crystal jitter‑reduction only as high as 96kHz — this nevertheless offers the best sound of the bunch, giving you an effortlessly wide and deep soundfield. Having used all three for several weeks, I found that I couldn't personally live without the Lavry DA10... and it went straight on to the credit card!