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Benchmark ADC1 Analog to Digital Converter - ProSoundNetwork.com

Benchmark ADC1 Analog to Digital Converter

In the 10 years I have I known the Benchmark Media product line, I have found their digital converters, (designed by engineer John Siau) to be some of the best sounding that I have ever heard. From their 20-bit units from the late-1990s to the well-respected DAC-1 24-bit/96 kHz DAC, the company has pushed accuracy instead of marketing hype. The new ADC1 stereo A/D 24-bit/192 kHz sampling converter is no exception.
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Fast FactsApplications: Studio, post production

Key Features: Two-channel; up to 24-bit/192 kHz; JitterLock circuitry; single-wire digital output for 176 kHz and 192 kHz; three-way gain adjustment; Main and Auxiliary outputs; word clock.

Price: $1,749

Contact: Benchmark Media at 315-437-6300; www.benchmarkmedia.comIn the 10 years I have I known the Benchmark Media product line, I have found their digital converters, (designed by engineer John Siau) to be some of the best sounding that I have ever heard. From their 20-bit units from the late-1990s to the well-respected DAC-1 24-bit/96 kHz DAC, the company has pushed accuracy instead of marketing hype. The new ADC1 stereo A/D 24-bit/192 kHz sampling converter is no exception.

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Features

Priced at $1,775, the ADC1 matches the half-rack size of the DAC1 and is a full-featured A/D that offers not only 24/96 specs, but Benchmark's signature UltraLock jitter immune circuitry, single-wire 176 kHz and 192 kHz digital output, internal word clock, a host of I/Os and flexible controls. The unit was originally introduced in 2002, but has taken a while to get to market.

The rear panel includes two balanced XLR analog input connectors, four digital outputs Ñ single-wire XLR digital output, optical output jack; independent or parallel-to-main output auxiliary digital output BNC, and a BNC sync input that accepts AES, SuperClock or word clock. There is also a BNC word clock output.

The front panel includes mode switch, meter display switch, first-stage left-gain switch, first-stage right-gain switch, left and right-gain trim pots, left and right- variable/fixed gain switches and a 41-step detented rotary gain control for each of the two channels. The first-gain switches enable either 0, +10 dB or +20 dB ranges. Gain can be set via the large variable channel knobs or the 10-turn input trimmer pots.

The left-side, nine-segment LED display indicates the selected sampling frequency. The word length is fixed at 24 bits on the main output, but is adjustable on the auxiliary output. The overall level is indicated by the nine-LED segment-per-channel meters. The meter switch allows the level to be indicated in -6 dB or -1 dB steps. The peak hold function duration is adjusted via the meter switch.

The ADC1 other features include SMUX output for either two channels of 24-bit/88.2 kHz or two channels of 24-bit/96 kHz audio on a normally 20-bit multichannel Alesis ADAT.

A word should be said about Benchmarks UltraLock jitter immunity circuit. The Benchmarks have always measured well Ñ even with interface jitter interjected into the testing process. The result has always been clean sounding conversion without the smearing that jitter can impart (check out all the ADC-1's measurements on page 16).

In Use

I used the ADC1 with two recording rigs: the TASCAM DV-RA1000 master recorder at 24-bit/96 kHz, and my Mac G5 using BIAS Peak at 24-bit/96 kHz. The interface for the ADC1/G5 connection was the Lynx 22 PCI-X card.

Since the Benchmark is one of the new breed of digital converters outputting 176 kHz and 192 kHz sample rate digital audio via single XLR cable, I could not record at those sampling frequencies into the TASCAM or the G5. The TASCAM requires two-wire output from external devices to accept 176 kHz or 192 kHz sampling rates and the Lynx 22 card supports only 96 kHz through its single-wire digital input.

The ADC1 is mostly straightforward and easy to use, and the manual is very detailed and chock full of specs and illustrations. The Benchmark, however, is one of those designs that requires manipulation of toggle switches and deciphering LEDs to select the sample rate. (Why can't we just get a display that says 24-bit/96 kHz, 16-bit/44.1 kHz, etc.?).

Anyway, once I learned that column 1's first two LEDs represent 48 kHz and 44.1 kHz respectively and column 2's first two LEDs represent 4X and 2X, I figured out how to toggle the mode switch to give me the sampling rates I wanted.

I first recorded the analog output of my Esoteric DV-50 DVD-A player into the ADC-1/DV-RA1000 combo at 24- bit/96 kHz. The material included prerecorded DVD-As and my own high-res acoustic guitar recording DVD-As using the Nightpro PreQ3 and a set of Audix SCX-25 microphones.

I played the material back via the Esoteric's excellent upsampling DAC as well as the Benchmark DAC1 24-bit/96 kHz converter. To play back the material on the Esoteric, I took the recorded 24-bit/96 kHz DVD+RW from the TASCAM transferred it to Minnetonka Bronze on the Mac and burned the audio onto a DVD-A, which was then played on the Esoteric.

After a few listening sessions, I was impressed. Using my high-end monitoring system with the Bryston amp, Legacy Focus ribbon speakers and a Pass Labs Class A preamp, I could not here the difference between the original DVD-As and the Benchmark one-generation copy of those recording. On the Benchmark converted copies of my best DVD-As, the nuance, space and realism of the recording was duplicated exactly from the original.

On original recordings of acoustic guitars, including a new Taylor concert-sized 712, the ADC1 transferred all the shimmer of the guitar and sound of the room space that could be heard during the performance, and there was no hint of harshness. The finger squeak decay from the guitar playing to the gradual fadeout of room reverb, this converter relayed all the information that was there. Stereo imaging at these high sampling rates is stunningly open. If you have the caliber of mics and preamps to make the best recordings, the ADC1 captures it in all its glory!

For those who are going to use multiple ADC1s for critical recording, I think they will be quite satisfied. For those who want it for archiving, mastering or other stereo tasks, the under $2,000 price per unit should make it attractive for those uses as well.

I wish it could have been a little closer in price to the DAC1, which is under $1,000, but the folks at Benchmark said it is not possible to US-manufacture this caliber of A/D converter at pro audio industry quantities at a lower price

Besides the pristine audio of the ADC1, I liked the word clock I/O and the auxiliary output, which parallels the main 24-bit output or outputs a separate simultaneous digital signal at 16-bit/44.1 kHz or 48 kHz. You can record high res and CD quality at the same time.

My only quibble with the ADC1 is the same one as I had for the DAC1: the lack of a power switch. I know that it is built to withstand "all-the-time-on" status, but sometimes I like to turn off a component without pulling the plug, or turning off the entire power strip.

Summary

The ADC1 was a long time in coming since its original announcement in 2002, but it has been worth the wait. Though not the bargain the DAC1 is at $975, the ADC1 converter at the higher bit rates is about as accurate and artifact-free as I have ever heard. The Benchmark ADC1's sonic qualities are stunning; the converter has the ability to realistically reproduce all the fine inner detail and presence subtitles that only the best high-resolution converters can. Impressive. Put a set of these in your Pro Tools rig.