Antelope Audio Pure2

We take Antelope’s latest mastering–grade converter and monitor controller for a spin

Antelope Audio may be a fairly young company but they’ve garnered an enviable reputation both for their expensive high–end A–D/D–A converters and master clocks, and more recently for their Orion 32 and Zen Studio audio interfaces, which draw on the same technology and offer very impressive value for money. As a happy Orion 32 owner, I jumped at the opportunity to evaluate their new Pure2, a stereo A–D/D–A converter with built-in monitor controller and USB audio–interfacing facilities.

Overview

Like all Antelope Audio’s products, the Pure2, with its metal buttons, sleek layout and OLED display, has an appealing, professional feel. The front–panel layout is clean and simple, with a power button, LEDs indicating the digital sync source, buttons for changing the sample rate, a volume knob, a button for toggling between monitor or headphone volume control, three preset buttons and a headphones output. The display features three level meters, which show the analogue, USB and digital input levels, as well as indicating the clock source and currently selected sample rate. Although quite small, the level meters have an accurate response and provide a very clear indication of the signal level.

The rear panel is rather more densely populated, with the following connections, running from left to right: AC power input, word-clock input, 10M input (which makes it possible to synchronise the internal clock with Antelope’s 10MHz ‘super reference’ clock), Toslink, S/PDIF and AES3 inputs and outputs, USB port, eight word-clock outputs (which allow the Pure2 to serve as a master clock) and, finally, two analogue XLR/TRS combi inputs, two analogue XLR main outputs and two TRS monitor outputs. The analogue connections are accompanied by small trim pots that allow the user to fine-tune their levels manually.

Control Panel

The included software control–panel utility automatically ensures that all software is updated to the latest version, assuming the studio computer is connected to the Internet. The control panel’s GUI is divided into four tabs, the first showing the volume settings for the main, monitor and headphone outputs, of which the last two have associated mono, dim and mute buttons. The source for each output can be selected individually, thus it’s possible to choose to listen to the USB 1–2 outputs (which could be the main stereo mix), while the headphone output is set to the USB 3–4 outputs (for example, to send a cue mix to the artist’s headphones). It’s also possible to monitor the analogue inputs while a stereo mix is sent from the DAW to the analogue outputs. This is desirable in a mastering situation, when a mix may need to be processed in the analogue domain, then recorded through the Pure2 and the result monitored in real time. By assigning the DAW software’s monitor outputs to the Pure2’s monitor outputs, it’s possible to listen to the digital processing applied after the analogue processing, making Pure2 a competent mastering tool.

Nifty connections apart, the monitor-control functionality is rather basic. For instance, it’s not possible to monitor the analogue inputs before the signal passes through the A–D converter. In Antelope’s defence, though, if you require more comprehensive monitoring control they offer a good dedicated analogue monitor controller, the Satori, which would make a great companion for the Pure2.

In addition to the analogue connections, the Pure2 features USB, AES3, S/PDIF and Toslink I/O, as well as offering eight word–clock outputs which allow it to be used as a master clock.The Pure2 offers sample–rate conversion on the digital inputs, making it possible to connect a CD player, or older digital devices that can’t be digitally slave sync’ed. The A–D and D–A converters share the same clock source, so it’s not possible to record at 96kHz and monitor at 44.1kHz — but you could do that with a pair of Pure2s, and the price tag makes that possible, for professionals at least, without the need for a second mortgage!

When the Pure2 is used as an audio interface, the drivers make four outputs and two inputs available to your DAW software. Without the USB connection, it’s basically a stereo device, though, and only one digital connection can be chosen at a time. This means that it’s not possible to feed the main outputs via AES3 and the monitor outputs via S/PDIF, which will limit its suitability in some more complex studio setups.

Since the metering on the front panel is very small, there’s also a large level meter at the bottom of the control-panel software, and this can display the level of the analogue, USB or digital inputs. As a young sound engineer working at the Swedish Broadcasting Corporation, I was taught to be almost manic about checking levels using only the best metering on the market, so it’s fair to say I’m picky, but this software metering is a bit too ‘flickery’ for my taste, and the release too quick. It also lacks clip indication. It’s not bad, but it’s not as good as most dedicated metering plug–ins or the custom–built level meter sitting next to my computer screen.

Conversion Therapy

Like most converters, the Pure2 can handle sample rates up to 192kHz. The A–D converter is interesting because it utilises a Burr–Brown PCM4222 chip, which, to my knowledge, hasn’t been used by many other manufacturers. The main outputs are also equipped with Burr–Brown D–A converters, but this time with a stereo D–A converter chip for each output: summing the two outputs of each chip helps to reduce both the distortion and noise levels. This might not be a new idea (both Weiss and Benchmark, for example, have been doing this for years) but it’s a good one! The monitor outputs are equipped with a single D-A converter chip, so the sound quality isn’t quite as good on paper — but when I switched back and forth between the main and monitor outputs, I could detect only a marginal difference in sound quality. The monitor outputs sounded comparatively a little restrained in the transients, the mid range was a little flatter and the stereo panorama seemed a hint narrower. The difference was so slight that I wouldn’t bet on being able to hear the difference in a blind test, though I wonder if I might be able to pick the ‘right one’ by listening to the difference in stereo width.

The analogue I/O are factory set to a maximum level of +20dBu but, by engaging manual mode in the control panel, the maximum level of each analogue connection can be adjusted between +8dBu and +26dBu, using the trim pot on the rear.

When I compared the main outputs with those of my Benchmark DAC2, the Pure2 stood up really well. Listening to Paper Airplane by Alison Kraus & Union Station, recorded and mixed at 24–bit/96kHz by one of my favorite mixing engineers, the late Mike Shipley, the guitars sounded just a little bit brighter and crisper, while losing a little naturalness. The same applied to Alison’s fragile voice, which sounded to me a little ‘harder’ through the Pure2. The depth in the mid range, however, is impressive and on the verge of being as good as the DAC2, something I also noticed when playing ‘Chan Chan’ by the Buena Vista Social Club, also recorded and mixed in 24/96. The soft analogue mix made by Jerry Boys actually sounds a little fresher through the Pure2 — the mid range has a depth and definition that portrays the Cuban music in a very nice way. The low–end dynamics show no sign of distortion or bandwidth limitation, and it’s a joy to audition this on my active four–way speaker system. The stereo width is a tad narrower than with the Benchmark DAC2, but you have to take into consideration that although the Benchmark device costs about the same as the Pure2, it is only a two–channel D–A converter.

The headphone output of the Pure2 is equipped with its own D–A converter, and compared with the headphone output of the Benchmark DAC2 it sounds pretty good. Listening to Toto’s ‘I Will Remember’, the toms didn’t have quite the same spread and Steve Lukather’s vocals sounded a little sibilant, but the sound stage was still very nice. Trying out an old pair of 600Ω AKG K240 cans showed that the headphone amp has plenty of power.

In order to compare the quality of the inputs I used two interconnected analogue summing boxes (an eight–channel Dangerous Music Mixer and a twenty–channel Inward Connections MIX690) to produce a thick and detailed analogue mix to be recorded via both the Pure2 and the Mytek Stereo192 A–D converter that I normally use. Comparing the two recordings, the Mytek sounded a little ‘meatier’ and softer, while the Pure2 produced a smoother, more defined mix, with improved stereo width. This is almost a case of comparing apples with oranges; it’s less a case of which is better or worse than which you like the most.

The Pure2’s control-panel software, which allows remote control of the unit, as well as offering an indication of settings and larger meters than on the hardware.According to Antelope, the Pure2 has been designed to cope with some clipping of the analogue inputs. I find it a bit kooky to rate digital converters — which, after all, are designed to have the same degree of accuracy as medical equipment — based on how they perform when pushed beyond their limits, but it remains a popular practice to ‘push’ converter inputs into clipping, thus squeezing the dynamic range and allowing you to raise the average level of a mix. Occasional clipping is handled very well — indeed, clipping the inputs by about 3dB shows that Pure2 can handle excessive levels better than my Mytek ADC.

Clocking On

A big part of this unit’s sound quality can probably be attributed to Antelope’s ‘Acoustically Focused Clocking’, which is achieved by placing the clock circuit inside an oven that maintains a constant temperature (64.5 degrees Celsius). The oven–baked clock circuit is very accurate and with those eight word-clock outputs, this makes the Pure2 a perfect digital master clock in the studio. If this isn’t enough, the Pure2 can be hooked up to Antelope’s 10M Atomic Clock. If only it had the ability to wake up my kids in the morning too

Monitor Controller

Using the front-panel volume knob to change the monitor volume produces a faint clicking sound inside the Pure2. This is the analogue relays that are used to attenuate the signal level without affecting sound quality. The display on the front shows the attenuation in decibels, which provides the opportunity to work with calibrated monitor volume. How does this affect workflow? More than you might think! Let’s say you increase the volume about 8dB to help you focus on controlling the low–end. You can go back to exactly the same monitor volume as before. My current monitor controller also has a volume display and I can’t emphasise enough how much this helps me when mixing.

At the push of a button, the volume knob switches to control the headphone volume, which also has a volume display — a great help during long mixing sessions, as when your ears are tired and you start raising the volume, it will show on the display. Pressing the volume knob mutes the monitor or headphone outputs, depending on which one is presently chosen.

As An Interface

During the test period, I experienced no problems using the Pure2 as an interface. At the minimum buffer size, Cubase Pro 8 reported a round–trip latency of five milliseconds, which is decent for a USB interface. The only tiny disappointment I’ve found so far is the fact that the digital sync source isn’t saved in the presets — this should be easy to fix in a firmware update because it works just fine in the same company’s Orion32 interface that I already own.

Pure Brilliance?

Antelope Audio’s Pure2 provides a tailored solution for the small mastering studio or music producer who demands high sound quality. There are plenty of connections on the back and the Pure2 can be integrated seamlessly as a digital converter and monitor controller in a commercial studio. Also, it may become the centrepiece of a small studio, acting as a monitor controller and audio interface. The monitor controls are simple but effective, and few other converters or interfaces have analogue relays to attenuate the speaker volume. Don’t be fooled by the price tag: the Pure2 ranks amongst the very best converters on the market, at a price that makes it just about obtainable for us mortals who just want the best possible sound quality.