Digital Processor Reviews

Sony Classical's head of engineering, David Smith, is a man whose opinions on sound quality I have come to respect. So when David e-mailed me a year or so back, enthusing over a new DAC he'd heard, I paid attention. When Lavry Engineering contacted me about reviewing their DA2002, I didn't need much persuading.

Lavry...
I was familiar both with Lavry Engineering's pro-audio components, under its older name of dB Technologies, and with designer Dan Lavry, from his often outspoken, tech-heavy postings on the Internet newsgroup rec.audio.pro. You can find theoretical white papers written by Dan on the Lavry website, discussing such things as word-clock jitter (he's against it) and high sample rates (he's against those, too, at least as far as quadruple rates such as 176.4kHz and 192kHz are concerned).

The DA2002 is Lavry's first consumer product, and is housed in a small chassis with a gold-plated front panel. It incorporates Dan's lateral thinking on audio circuit design (again, see the Lavry website), and handles sample rates from 44.1 to 96kHz. Both balanced and unbalanced analog outputs are provided, and absolute polarity can be inverted with a front-panel button.

...Engineering
The DA2002's power supply is based on two small toroidal transformers. These are mechanically damped by being clamped by the top panel, and are followed by some beefy rectifier diodes, the usual reservoir capacitors, and four three-pin regulator chips that use the chassis as a heatsink.

The three data-input jacks are each buffered by a small transformer. The clock circuit uses two crystals, one for 44.1kHz/88.2kHz data, the other for 48kHz/96kHz data, and these appear to be under the control of an Analog Devices 12-bit DAC, which matches the rate at which the incoming data are clocked out of the jitter-reducing buffer to the long-term average of the incoming datastream. The data are then processed by a Motorola DSP56002 DSP chip, which I assume handles the low-order upsampling and the digital low-pass filtering.

The signal path downstream of the DSP chip is complex. The only DAC chips I could see were a pair of Analog Devices AD7538s. This is a 14-bit part, according to its data sheet; the DA2002's manual states that these are used to calibrate the DACs. So where are the real DAC chips?

The key to the DA2002's D/A conversion is actually buried beneath a power resistor. Rather than use an off-the-shelf DAC part, Dan Lavry uses a custom-made network of laser-trimmed thin-film resistors; the big resistor acts as an oven, heating the network to its working temperature. Each time the DA1002 is powered up, this network is calibrated using the AD7538 DACs and multiplexer chips, using, I imagine, data stored in the adjacent EEPROM chip.

The end result of this activity is that, somewhere within this forest of chips—the resistor network is embedded in an array of Burr-Brown OPA177 bipolar op-amps and Analog Devices AD744 BiFET op-amps—an analog signal that accurately corresponds to the input data emerges, and is fed to a seven-pole analog reconstruction filter and the DA2002's output stages. Burr-Brown OPA627 Difet op-amps (driven by the crystal oscillators mentioned above) are used as sample-and-hold deglitchers ahead of the balanced filter and output circuitry, this using discrete transistors as well as ICs and carried on a small double-sided daughterboard. The two unbalanced outputs each appear to be realized with a Burr-Brown OPA134 Sound Plus op-amp chip.

Sound quality
When I first turned on the Lavry DA2002, it took about five minutes to decide that all was okay with its operating parameters. During this process, first the top two orange sample-rate LEDs flashed, indicating that the DAC resistor network had not yet reached its equilibrium temperature. When it had, the bottom two orange LEDs flashed, indicating that the DA2002 was going through its DAC calibration routine. At the end of this process, the DAC scrolled through its green input LEDs until it found a source carrying valid data, at which point the appropriate input LED remained lit. When presented with two sources, the input button can be used to select the desired source in the usual way. It also has a Mute position.

Out of the box, the DA2002's CrystalLock® jitter-rejection buffer is in-circuit. This can be switched out or in by holding the Polarity button for 1.5 seconds; I did all my auditioning with CrystalLock engaged.

The first disc I played was the Hi-Res Music DVD-Audio of the Ray Brown Trio's Soular Energy (HRM 2011). This disc is unusual in that it allows an in-the-clear 24-bit/96kHz datastream to be transmitted from the DVD player's digital output (if it has one that will handle 96k data). The Lavry had no trouble locking to my Technics DVD-A10's digital output via a 10' length of AudioQuest's VSD-4 S/PDIF cable—and yes, while I admit this disc was mastered from an analog original, there was an analog-like "ease" to the Lavry's presentation. The sound of Ray Brown's double bass had a satisfying purr to its leading edges, yet the upper register of Gene Harris' piano didn't sound too etched.

The Technics has overall proved a disappointment as a disc transport since I purchased it at the end of 2000. Yet it proved more than adequate feeding the Lavry DAC, which seems to suggest that the DA2002's data receiver is effective at cleaning up the timing of the data fed it. The result was an almost "tubelike" midrange smoothness to the Lavry's sound.