28 l April 2013
www.psneurope.com
Zealous converts studiofeature
Phil Wardtraces the growing importance – to everysector of pro audio – of the humble converter chip
Merging Technologies’ Horus was launched last year
BRIDGING THE God-shaped hole between the analogue and digital worlds is up there with the Higgs boson. As Rane Corporation’s Dennis Bohn explains in his treatise Digital Dharma of Audio A-D Converters, nothing is more important: “Once a waveform has been converted into digital format,” he writes, “nothing can inadvertently occur to change its sonic properties. The point being that sonically, it begins and ends with the conversion process. Nothing is more important to digital audio than data conversion. Everything in between is just arithmetic and waiting. We could go so far as to say that data conversion is the art of digital audio while everything else is the science, in that it is data conversion that ultimately determines whether or not the original sound is preserved.”
DEER GOD
But first, Bulgarian Antelope. Traditional hunting fare, served with… actually some pretty solid converters made in Sofia, and distributed internationally including in the UK by Unity Audio. Antelope’s converters use ICs made by Burr-Brown, now merged with Texas Instruments, as explained by Antelope’s Gary Clarke, international customer support team leader. “We chose these after running tests on a whole heap of different chips from India, Germany and
so on,” he reveals. “But we’re looking for clarity and to be true to the analogue sound. If the tests show that the sound is overly colored, or is warmed artificially, we wouldn’t choose it. So it comes down to which chip performs best according to our testing.” Priorities include higher sample rates, extensive monitoring capabilities, versatility of options
to 192kHz, 384kHz, whatever… quite amazing. There’s a pro mastering version with balanced XLR outputs too – perfect for really precise volume control off the back of a DAW.” At the other end, Eclipse
offers flexible input and output permutations, accurate meters, stable clocking, 24-bit resolution and very high sample rates.
equivalent DAC, called the B2 Bomber, and there’s a modular, multichannel model for either MADI or Pro Tools called The Mothership, appropriately enough. “What’s interesting about Burl is the emphasis on the analogue section of the converter: there are transformers on the front end. Sonically, it appeals especially to
“Most manufacturers would probably claim to be transparent, and by and large you don’t want to be chopping and changing your interfaces, but there’s a growing habit of varying them”
Kevin Walker, Unity Audio
for the user and integration with the latest in Antelope Audio’s clocking technology: the Eclipse stereo ADC carries two independent clock generators with ultra-low jitter and ‘acoustically focused’ clocking. Unity founder Kevin Walker points out that these converters increasingly bridge a gap between pro and other markets, even domestic. “They have pretty high sample rates,” he says, “up to 384kHz – not that many people use that in production. Antelope’s DACs are called Zodiac, very prestigious in residential, and some have upstreaming capability: you can play files off a hard drive and up-sample them
“This is the traditional market,” says Walker. “The Eclipse won Best Product at the AES Convention in New York last year, but the other converters proving strong for us come from US manufacturer Burl. A couple of years ago they came out with a separate, stereo ADC and an
AKM Semiconductor,
www.akm.com Analog Devices,
www.analog.com Cirrus Logic,
www.cirrus.com Fairchild Semiconductor,
www.fairchildsemi.com Holtek Semiconductor,
www.holtek.com Intersil,
www.intersil.com
the rock and roll market – it’s the closest converter I’ve found to sound like an analogue tape machine. Not many ADCs have that warm, round bottom end. But it might not be the first choice for classical recording.” This raises an interesting question: how many markets are
CONVERTER SUPPLIERS’ GUIDE
Linear Technology,
www.linear.com Maxim Integrated Products,
www.maximintegrated.com Microchip,
www.microchip.com NEC,
www.nec.com NJR Corporation,
www.njr.com Renesas Technology America,
www.renesas.com
Sony,
www.sony.co.uk That Corporation,
www.thatcorp.com Texas Instruments,
www.ti.com Wavefront Semiconductor,
www.wavefrontsemi.com Wolfson Microelectronics,
www.wolfsonmicro.com
seeking a truly neutral, flat converter; and how many might in fact discover that some are ‘more neutral than others’. “I do know quite a few people who use more than one converter,” Walker says, “specific to the application. Most manufacturers would probably claim to be transparent, and by and large you don’t want to be chopping and changing your interfaces, but there’s a growing habit of varying them. If you work in one genre most of the time, you’ll be tempted to pick one over another not for its transparency, but for its colour.”
AT THE CHIP SHOP IC suppliers feed every corner of industry. Pro audio is small fry, really, but that doesn’t prevent its specialists from seeking out perennially the finest solutions available. Mikael Vest, sales director at NTP Technology in Denmark, since 2008 the home of Digital Audio Denmark (DAD), says. “Of course we try to select the best supply we can. Currently we’re using the top models converter chips from Cirrus Logic ICs on the A to D, and Burr- Brown for the D to As. Issues arise all the time, especially in D to A in fact, and this is definitely a game in which the real ‘state-of- the-art’ conversion matters a lot.” One crucial criterion for DAD
is that there must be access to the modulators within the IC, in order to apply proprietorial optimisation for pro audio. “Modern chips are delta-sigma types,” continues Vest, “where you have a modulator, very high speeds and filtering available to adapt the circuits. And, since in all our products we support Digital eXtreme Definition (DXD), with 352.8kHz and 384kHz of sampling, we need to access this modulator so we can realise our own filtering to handle the down-sampling – both for the A to D and D to A. The modulator runs at a much higher sampling rate by default, and has to be adapted for each sample rate. “Normally this happens within the chip itself, and many
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