Converters and Clocks Engineers on Their Choices

In the workstation world, the point at which an analog signal is converted to digital is a critically important link in the signal chain.
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Needless to say, A-to-D and D-to-A converters run the gamut from budget to stratospherically expensive. Not surprisingly, the quality of a particular converter runs a corresponding path, though personal taste and other criteria are part of the equation as well.

Equally critical in any digital recording system is the master clock, or synchronizer. Stable and consistent sampling is essential to avoid jitter and allow an accurate A-to-D conversion, from which all subsequent work — processing, editing, mixing, and mastering — follows.

A sampling of audio professionals is likely to produce multiple references to the same handful of products; unlike, say, mixers or microphones, there aren't too many players in the converter and clock categories, and an even smaller number reside at the pinnacle, as measured by popular opinion.

Though the ears have it, many professionals also use the mostbang-for-the-buck yardstick. Converters can be very expensive; for the home studio owner, a DAW rig's onboard converters and internal clock may be adequate. But if the highest-possible sound quality is your goal, can you afford not to consider external converters and clocking?

Tim Hatfield (left , pictured with artist Rob Arthur) says using the Apogee Big Ben clock with Digidesign 192s makes "such a big difference, it's unbelievable." "We've put half of our money into speakers and the other half into converters," says Scott Hull of New York-based mastering facility Masterdisk. "Nine or 10 years ago I came to find the top-of-the-line Prism converters. When I moved to Classic Sound, I went from dCS to Prisms and just loved them. I can't master without them.

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"If I had to work off the dCS's," Hull adds, "I would be able to. But the Prisms have a slightly more neutral, slightly more interesting bottom end. I'm really kind of stretching for differences, because it's somewhat program-dependent. I could find another set of speakers that might sound better, but I know these so well; that's why I use them. I feel the same way about the converter."

Familiarity, for Hull, is most important, neutrality a close second. The Prism AD-2 and DA-2, he explains, "tend to be a tiny bit more neutral, in that they don't feel hyped in the top end, they don't feel hyped in the bottom end, and that gives me a lot of latitude. I work on everything from extreme avant-garde to classical, and death metal in between. It needs to be very versatile, but unlike some of my contemporaries, I get very used to a particular sound of converters and don't change it very often. I don't try to match up the converter with the music as much as some people do. It's sort of an extension of my monitoring system and my speakers; I know how the other things that I put in the chain are going to interact with the converter. I feel like I've learned the converter so well that when I put something else in, I find myself just EQ'ing around it, EQ'ing to compensate for it."

Paul Antonell, owner and engineer at the Clubhouse Studio in Rhinebeck, New York says that, "after numerous listening tests and sessions using various converters — Apogee, Digidesign, Lynx, Lavry, Lucid — we decided, ultimately, that the Digidesign 192 is the most seamless, and best bang for the buck. We also decided to buy a Lynx Aurora 16 as an additional set of in and out. The Lynx sounds undoubtedly better than the Digi's, but when we purchased our Pro Tools system, the Auroras were not released yet.

Paul Antonell of the Clubhouse in Rhinebeck, NY, finds the Digidesign 192's conve rters to be the most seamless and best bang for the buck. He uses an Apogee Big Ben clock; the studio also employs Lynx Aurora 16 converters. "If we were to buy a new system now," Antonell feels, "we'd likely purchase the Lynx to outfit fully. They sound great, and while they may not be the absolute last word in converters, the price-to-performance ratio is amazing! That being said, we've been using our Digi 192 interfaces for four years now, running them off an Apogee Big Ben clock, and we couldn't be happier. They sound 'good enough,' easily, and the operation with Pro Tools is obviously seamless.With the Big Ben, the 192 becomes a very good performer, and good enough for us not to search out more expensive options for diminishing returns."

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"I currently use Pro Tools|HD3 Accel with two Digidesign 192 converters, no external clock," says Los Angeles-based producer Brad Wood. "I run the outputs of the converters into a Tonelux console and back into Pro Tools for stereo mix. I usually track at 88.2k/24-bit and find that to sound great. I previously had Apogee AD-8000 converters for my Pro Tools MIX setup, but found the 192s and higher sample rate more pleasing to listen to."

Dave McNair, a mastering engineer at Masterdisk who was previously a producer and recording engineer and continues to mix, feels that "when you get up in the region of the really high-end converters, they're all pretty good; they just have minute differences. I'm really into the Lavry Gold AD122-96 MKIII, which is the A/D. Then I use the companion D/A, the DA924. I compared them to a lot of converters, and I just love the sound of them. I know that when I hear the Lavry stuff, everything is super effortless-sounding. That's what I like about them. For the monitoring D/A," McNair adds, "I use the current version of the Chris Muth D/A that is built into the Dangerous Monitor."

"When I have needs for another, alternate converter in our production rooms or other circumstances," says Hull, "the Benchmark DAC1 also comes up fairly high."

An external clock can have a dramatic impact on a DAW-based recording system, audio professionals assert. "When a DAW is crunching numbers," says New Yorkbased engineer Tim Hatfield, "a good clock keeps them more 'in time.' The clock is just much more rigid, it shouldn't waver at all. If you think about it in terms of music, it's right on the grid, not stuff with swing. In this case, you don't want the clock to swing — it's not a drummer! When it comes to a clock, you want your drummer right on the grid.

"I just use the converters that are in my [Digidesign] 192s," Hatfield explains. "But I do use the Apogee Big Ben, and I think it makes a ton of difference. When I first got it, I had the MOTU 24I/O — 24 ins and outs— and also my 192s. At the time, I had kept the MOTU rig, because I still had projects going on Digital Performer. But the clock, with that, made such a big difference, it was unbelievable."

In his home studio, Hatfield makes the A/D conversion in a Focusrite ISA430 MKII Producer Pack system "and go digitally into a Digi 002," he says. "I use that digital input as the clock source. I don't know if it makes that much difference — I never A/B'd it — though in my mind it does. Plugging in the Apogee clock to the Digi 002 makes a huge difference, too. When you have a really great clock it's amazing, and I don't think there's a better one than the Apogee Big Ben."

"The Antelope Audio Isochrone 10M Atomic Clock is very expensive, but a really amazing box," Hull offers. "It's hard to not buy one once you've heard it. It really tightens everything up. It makes the converters generally sound a little bit better. It has its best, most profound effect — like any clock does — in a situation where a clock's kind of unstable to begin with. When I'm distributing my Prism AD-2 clock around the room, that's pretty damn stable, so the differences there are noticeable, but just; it's noticeable by a mastering engineer's standards.

"It flies in the face of convention," Hull adds, "but I would go as far as to say the Big Ben wasn't better, [but] it was at least equivalent. Big Ben is good, and it'll make a multitrack sound better instantly. But the Antelope atomic clock is really out at the extreme."

Christopher Walsh is the recording editor for Pro Sound News and the associate editor of Pro Audio Review.