Fast FactsApplications: Studio, Post-Production, Mastering, Remote Recording
Key Features: 16-bit, 24-bit; up to 96 kHz; Acoustic Bit Correction technology; Digital Soft Saturation processing
Contact: Lavry Engineering, 206-842-3552, www.lavryengineering.com.When the dB Technologies "Gold" AD122, from designer Dan Lavry, first appeared on the studio scene in 1995, it provided a glimpse into the future of digital audio. Its performance, even then, approached the theoretical limit of what is physically possible for an analog to digital converter. Better clocking and 96 kHz sampling were later added in the MkII. The newest iteration, the LavryGold AD122-96 MKIII, carries on the tradition with specs that are better yet, a new power supply, greatly reduced heat dissipation, and improved reliability. Versatile features such as Digital Soft Saturation, protection from full-scale overs, dither selection, and precise metering combine to make the AD122MKIII a nearly complete mastering system. The quality of sound is nothing less than you'd expect from a device of this pedigree. Earlier AD122-96MKII units can be upgraded to MKIII.
In conversation, Dan Lavry is understandably protective about the proprietary aspects of his design, but he is definitely forthcoming about his philosophy. Its fundamental tenet can be summarized as "waveform in equals waveform out." Lavry's primary means of achieving this goal are total integrity in the analog stage, minimal jitter at the converter stage, and precise amplitude and phase linearity throughout. A few specific examples are that a pure discrete Class A low-noise analog stage is used to drive the converter's sample-and-hold circuit; an ultrastable crystal clock, tuned according to the designer's own research into the psychoacoustics of jitter, is located as physically close to sample-and-hold as possible; and the system employs a self-calibration technique to compensate for component drift due to temperature and aging.
The AD122MKIII operates at standard sampling rates up to 96 kHz with a remarkable dynamic range of 127 dB unweighted, and a vanishingly low total harmonic distortion spec of .0008% for signals averaging below -6 dB full scale. The output word length can be set for any value between 16 bits and 24 bits. Word length reduction is accomplished with Lavry's own highly effective "Acoustic Bit Correction" dither in conjunction with four types of noise-shaping. Flat dither is also available and is recommended for situations involving downstream processing or data compression.
When synchronizing to an external clock, two lock ranges are possible. For standard rates, a voltage controlled crystal oscillator is employed, enabling the converter to operate as a slave while still maintaining excellent low-jitter performance. For external rates that are farther afield, a wide-lock setting is available.
A key feature is Lavry's "Digital Soft Saturation," which emulates magnetic tape saturation. The algorithm is based on an exponential transfer function and operates on a sample-by-sample basis. Two curves are available, one that applies 3 dB of gain with saturation commencing at -6 dBFs, and one that applies 6 dB of gain with saturation beginning at -12 dBFs. Digital soft saturation enables conversion at high digital levels without the need for additional dynamics processing. For such brinkmanship there is also a "data limiting" setting that insures that the converter's final output is always at least one least significant bit below full scale. Consequently, downstream transfers will not register any digital overs.
Settings are also possible for DC removal and polarity inversion. A wide-ranging variable frequency tone generator and finely resolved level meter are onboard for accurate level adjustments.
My tests began with a series of live microphone recordings under the auspices of a New York-based audiophile production company. We used a single-point stereo mic feeding a pair of Tube Tech preamps. Output from the preamps went directly to a distribution line stage, and then out to the AD122MKIII and to two other comparably priced high-end converters. Our sessions, recorded at 96 kHz sampling, consisted of a jazz trio - piano, acoustic bass and drums - and a female vocalist accompanied by acoustic guitar and percussion.
In the top tier of converters, the level of resolution and detail is consistently excellent across the various brands; however, the subjective presentation of each is unmistakably different. Presumably, this is the result of the sum total of the many decisions each designer makes from conception to the final product. It is remarkable that the ear is still ahead of measurement in this regard and that a group of listeners can hear the same attributes and agree. In our blind preference tests, the AD122MKIII took the lead time and again. It was variously described as full, natural sounding, musical, and inviting. One comment was that it has the kind of sound that keeps you listening to the music. Clearly these were subjective responses. Another group of listeners with a different set of values might have found differently.
We thought that our ideal mic test might have been a little too easy for a machine designed to go up against physical limits, rather like road-testing a Lamborghini during rush hour on the Long Island Expressway, so we decided to throw it a curve ball. The manual states that the AD122 will accomplish extremely low jitter even on external clock, a condition that normally handicaps a converter. We ran some additional live passes with the Lavry slaved to the word clock from one of the other ADCs. None of us could really hear any degradation in the results, and the AD122MKIII won again in a blind preference test, even disadvantaged as a slave.
Lavry's mid-priced offering, the LE4496 "Blue" A/D, has become a deservedly successful product and the obvious question is: how does it compare with the Gold? My sources for this test were some analog-sourced DSD recordings played on an audiophile SACD player. Not an ideal test, but at least it was a level playing field. Blue did respectably well in holding its own against its richer brother. Blue has more heft in the upper bass than the Gold, which is more neutral by comparison, but Gold uncovered features in the sound that were not evident in the Blue playback. Gold had a finer focus. Details came forward such as the differentiation between keyboard and guitar lines playing in the same register or the particular voicing of strings in an overdriven rhythm part. A telling cue was that the analog tape noise in the 1958 classic by the Cal Tjader Stan Getz Sextet was obviously more defined in the high frequencies in the Gold conversion. There was more to hear from the LavryGold MKIII.
Since linearity is another of the stated goals of the Gold design, I ran some passes feeding both converters with program material reduced to an average level of Ð50 dB and then normalized the results to full-scale for comparison. To make matters more challenging, I captured at the single sampling rate of 24-bit/44.1 kHz and also at 16-bit/44.1 kHz using the AD122Õs Acoustic-Bit Correction dither set to Noise Shape 4. The source for this test was Getz/Gilberto on SACD, one of the most pristine and beautiful recordings of the analog era, engineered in 1963 by Phil Ramone. This SACD offers some of the most exquisite vocal and instrumental tones on record. This time the differences were dramatic. The AD122Õs low-level capture was significantly more life-like and forward sounding. Even the 16-bit file captured with the Gold's noise-shaped dither was a marked improvement over the Blue at 24 bits. Although the dither hiss was plainly audible in the noise-shaped track, the tone of the music was extremely close to that of the 24-bit conversion. While most pop recordings these days will never again see levels anywhere as near as low as - 50dB, if the goal is to capture an acoustic performance at full dynamic range, the AD122-96k MKIII is up to the task.
My final trials were directed to the Digital Soft Saturation feature. Feeding the MKIII an analog source with no dynamics processing other than digital saturation set to +6, I was able to get a clean sounding result that was easily in the realm of today's so-called commercially 'competitive' levels. In comparing this to a pass done with a well-known digital mastering limiter, the Gold-saturated pass was surprisingly free from pumping. Comparing the digital saturation capture with the original source at matched levels showed Lavry's dynamics algorithm to be very true to the tone of original mix, albeit obviously compressed.
In today's world of "good enough" audio, it is reassuring to know that there are still companies willing to invest their time and resources towards creating the best. For analog-to-digital conversion applications where wide dynamic range, ultra-low noise, and pristine musical fidelity are essential, the LavryGold AD122-96 MKIII is a clear winner.
Fast FactsApplications: Studio, Post-Production, Mastering, Remote Recording