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electronic MUSICIAN

APOGEE Rosetta 200

By Nick Peck | October 1, 2005

Apogee's Rosetta 200 is a 2-channel A/D/A converter that is capable of resolutions as high as 24 bits and 192 kHz. It can be used as a standalone converter with fairly sophisticated audio-routing capabilities or as part of a front end for digital audio workstations. The Rosetta 200 could be considered a sibling to Apogee's 8-channel Rosetta 800 (reviewed in the April 2005 issue of EM). The Rosetta 200, however, has a couple of tricks up its sleeve that set it apart: built-in sampling-rate conversion; 24-bit to 16-bit dithering; and an automatic level control, called Aptomizer, that maximizes gain structure during analog-to-digital conversions.

FIG. 1: The Apogee Rosetta 200 has two channels of high-grade A/D/A conversion and a multitude of routing options.

Button-Down

The Rosetta 200 is a heavy and sturdily constructed unit (see Fig. 1). All of its main controls are accessed from seven buttons, and holding the buttons down for a couple of seconds accesses the unit's auxiliary functions. Parameter settings are indicated by LEDs, including separate, spiffy 12-stage meters for the analog- and digital-output paths.

The Sample Rate button allows you to select one of Rosetta's six internal sampling rates or to engage external sync. The Sync button chooses the external sync clock source from the digital inputs. The Source button selects the master audio signal, which does not have to be the same as the master-clock source. The selected signal is then routed to all digital outputs simultaneously.

The Process button engages automatic sampling-rate conversion (to be added in a future firmware update) and 24-to-16-bit dithering. The Aptomizer button engages the analog level-control maximizer. Finally, a separate Source button routes a selected input source to the analog outputs. That means that Rosetta can simultaneously route different signals to the analog and digital outputs — a nice touch.

Out, In, Extend

The Rosetta 200's rear panel (see Fig. 2) features all the connections that you'd expect, such as two sets of balanced +4 dBu XLR stereo pairs for analog I/O. Two AES digital ins and two outs can operate in single- or double-wire format at rates as high as 192 kHz. S/PDIF in and out are included on RCA jacks, and word-clock in and out are on BNC connectors. Toslink optical connectors offer ADAT, S/MUX, and S/PDIF in and out. As an added benefit, a pair of MIDI jacks make Rosetta 200 a MIDI interface when used in conjunction with the company's FireWire extension card.

FIG. 2: The Rosetta 200''s rear panel has two sets of XLR analog I/O, AES, S/PDIF, word clock, ADAT, and a pair of MIDI jacks for use with the company''s FireWire extension card.

The Rosetta 200 can interface directly with your computer or DAW through a series of optional cards. Apogee's X-FireWire card, the logical choice for a native-based system, features two FireWire 400 ports. Drivers currently exist for Mac OS X Panther (10.3.7) and Tiger (10.4) and Windows XP Service Packs 1 and 2. Apogee also has a utility called FireMix, which has low-latency monitoring and various utility functions for the Rosetta. FireMix is free and available from Apogee's Web site.

The company also has extension cards for connecting a Rosetta 200 directly into Pro Tools|HD and Mix system core cards, offering an alternative to Digidesign I/O units. Giving consumers that type of choice is an excellent idea. Kudos to Apogee for selling a card that supports Pro Tools Mix-era hardware.

Coda

Apogee's Coda processing involves a trio of functions that enhance Rosetta's capabilities as a digital audio processor. Its current sampling-rate conversion is a high-quality real-time process for translating the rate of a selected digital input to the target rate of a digital output. (An automated sampling-rate conversion process, which will query incoming digital audio streams and convert them to the target rate, will be added in a future firmware update.) The UV22HR dithering process gracefully downgrades 24-bit signals to 16-bit. Sampling-rate conversion and dithering can be used in tandem to convert high-resolution masters to CD resolution in real time.

Coda's third function is called Aptomizer. This nifty feature allows you to maximize gain structure within the analog-to-digital conversion process, without worrying about digital “overs.” In Learn mode, Aptomizer analyzes the incoming analog source signal and automatically calibrates the line input level so that the peak signal is encoded at -0.5 dBfs. Turning off Learn mode and recording the signal during a second pass guarantees a robust digital signal that is free of digital distortion.

Rosetta also has Apogee's soft-limit technology, which applies a near-instantaneous limiter to signals above -4 dBfs. While soft limit is useful for real-time recording, I'd avoid that type of process for capturing preexisting analog material and use Aptomizer instead.

In Operation

Integrating Rosetta into my Pro Tools|HD system was a straightforward process. Rosetta appeared to my Pro Tools software as a Digidesign 192 I/O unit, and aside from some confusion around the labeling, it worked well. I plugged the analog outputs through a minimal monitoring chain into my Genelec 1031 monitors and listened to a variety of material at different sampling rates.

I enjoyed what I heard. The Rosetta 200 sounded glorious. I was able to pick out minute details in the music that I had not noticed before. The music felt smooth and unhyped across the frequency range, with clear highs and tight, focused lows. The stereo imaging was crisp and distinct; with my eyes closed, I could effortlessly place every instrument across the stereo spectrum. I even felt a sense of vertical height. Rosetta brings out what is best about digital audio: a clean, precise replication of the original signal.

In A/B tests between the Rosetta 200 and the Digidesign 192 at high sampling rates, I was able to notice subtle differences. Both units were routed directly into the monitoring section of a Digidesign Control 24, then into a pair of Genelec 1031A monitors in an acoustically tuned environment. Each unit was evaluated in internal sync mode, using high-quality reference material mixed on the scoring stage at Skywalker Sound.

To my ear, the 192 sounded less focused; however, it also sounded bigger and glossier, with a high-end sheen that I preferred. The Rosetta had a tighter sound, particularly in the low end, and the stereo field was razor sharp. But the material sounded slightly more pinched and constrained than it did on the 192. My personal conclusion is that the Rosetta 200 and the Digidesign 192 are excellent sounding I/O boxes, and choosing one over the other is a matter of personal taste.

I experimented with Rosetta's Coda sampling-rate conversion and 16-bit dithering by prepping some mixes from a recent recording session for CD. The recordings were of a funk jazz group produced with high-end gear and minimal processing.

I fed a version of the material from Pro Tools to the Rosetta, which converted the file from 24-bit, 192 kHz to 16-bit, 44 kHz. I printed the result to a DAT recorder and then fed the recording back into Pro Tools through the Big Ben's reclocking mechanism (see the sidebar “The Times of Big Ben”). I compared the Rosetta's version to tracks that had been sampling-rate converted using Digidesign's bounce-to-disk command, as well as the excellent shareware application, Amadeus II.

The differences were subtle yet unmistakable. The Amadeus-converted version felt flat and 2-D. The Pro Tools converted version was better, with more depth and a wider sound stage. The Rosetta-converted version had significantly more front-rear depth and was more enjoyable to listen to, though it was still a noticeable downgrade from the 24-bit, 192 kHz masters. Nonetheless, there is definitely something to Apogee's sampling-rate conversion and bit-dithering algorithms; if I were a mastering studio in pursuit of aural nirvana at 16-bit/44 kHz, I'd take a close listen to this box.

Final Conversion

There's no doubt about it, Rosetta 200 is a fine piece of gear. It has solid, excellent-sounding A/D/A conversion; decent digital-signal routing; and great conversion routines. Aptomizer is a cool feature, and the external card connections to FireWire and Pro Tools|HD/Mix offer great flexibility. At $1,995 for a 2-channel box, Rosetta 200 is not for everyone. But for a stereo mastering facility, a live-concert recordist, or an “in-the-box” computer musician who wants a taste of the good life, the Rosetta 200 should be on the short list of converters to check out.


Nick Peck is a father/composer/keyboardist/sound designer/engineer in the San Francisco Bay Area. He can be reached at nick@perceptivesound.com.


SIDEBAR

THE TIMES OF BIG BEN One necessity of the all-digital recording studio is a stable, high-quality reference clock that all devices slave to. If you have a complex, multi-device digital system, then Apogee's Big Ben may be a useful solution (see Fig. A). Big Ben features Apogee's most stable digital reference clock yet and offers a clean, virtually jitter-free clock source at sampling rates as high as 192 kHz. Big Ben has film pull-up/pull-down rates and variable rates in increments of as little as 1 Hz.

FIG. A: Apogee''s Big Ben has a jitter-free clock source at sampling rates as high as 192 kHz for multidevice digital systems.

Big Ben features two AES/EBU inputs and outputs (operable in single or double-wide mode), coaxial S/PDIF in and out, Toslink optical in and out (S/PDIF, ADAT, or S/MUX formats), a video/word-clock in, and six word-clock outs on BNC connectors. Big Ben can slave to any incoming clock signal, creating a stable, refreshed version that it passes to all its digital outputs. If Big Ben is slaving to a signal that contains audio information, such as AES/EBU, it will pass along the refreshed audio signal along with the clock to all outputs that support audio. For maximum flexibility, two of Big Ben's word-clock outputs can transmit signals at ½, ¼, 2, 4, or 256 times the master-clock source.

There has been much talk in recent years about jitter from poor clocking being a prime source of digital distortion. While internal clocks have been getting progressively better, Big Ben is a product specifically oriented toward providing the best reference clock. If you have a modest DAW and are looking to improve the sound of your I/O, can Big Ben make a difference? Probably so. But using Big Ben to improve the sound of an inexpensive A/D card might be like attacking a mosquito with a howitzer. You could be better off investing in a top-flight I/O unit. If, however, you have a complex digital setup with multiple devices slaving to each other, Big Ben is worth a serious look.


ROSETTA 200 SPECIFICATIONS
Analog Inputs (2) XLR
Analog Outputs (2) XLR
Digital Inputs (2) AES; (2) S/PDIF; (2) Toslink (ADAT, S/PDIF, or S/MUX); (2) Pro Tools|HD, Pro Tools Mix, or FireWire on optional card
Digital Outputs (2) AES; (2) S/PDIF; (2) Toslink (ADAT, S/PDIF, or S/MUX); (2) Pro Tools Pipe HD, Pro Tools Mix, or FireWire on optional card
Word-Clock Ports In, Out (BNC connectors)
MIDI In, Out (acts as MIDI interface only when optional FireWire card is installed)
Resolution 16 to 24 bits (with 24- to 16-bit dithering)
Sampling Rates 44.1-, 48-, 88.2-, 96-, 176.4-, 192 kHz
Frequency Response 10 Hz-20 kHz (±0.2 dB) @ 44.1 kHz
Dynamic Range 114 dB A-weighted (A/D/A)
THD + N -105 dB (AD), -103 dB (DA)
Dimensions 1U × 11.75" (D)
Weight 12 lbs.

PRODUCT SUMMARY


APOGEE
Rosetta 200

A/D/A converter
$ 1,995

OVERALL RATING (1 THROUGH 5): 4

PROS: Excellent sound quality. Flexible routing architecture. Great sample rate conversion and dithering. FireWire connectivity as well as direct support of Pro Tools TDM.

CONS: Relatively expensive.

MANUFACTURER

Apogee Digital, Inc.
www.apogeedigital.com

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