Field Test: Apogee Electronics Big Ben Master Clock
Dec 1, 2003 12:00 PM, By Michael Cooper
Apogee Electronics' Big Ben is a revolutionary master digital clock that does much more than preclude clicks and pops from tainting your audio tracks. Unlike other Word Clock distribution boxes that achieve only subtle reduction in jitter artifacts, Big Ben will make your converters sound dramatically warmer and smoother. Another bonus: Big Ben can even perform digital audio format conversions.
Big Ben owes its impressive clocking performance to proprietary technologies: Apogee's Direct Digital Synthesis process — an all-digital alternative to traditional phase-lock loop circuitry — generates clock frequencies with virtually immeasurable jitter. When synched to an external reference, Big Ben uses Apogee's Adaptive Loop Filtering to recondition the clock source and reduce jitter. (I found the improvement here to be audible, but subtle.) Thanks to SureLock technology, Big Ben continues to output clock signals at the last valid frequency received by an external reference signal that subsequently drops out, purportedly guaranteeing a fail-safe lock.
I/O AND SUPPORTED FORMATS
All of Big Ben's I/O connectors are found on the unit's rear panel. These include AES/EBU inputs and outputs (two each, for a total of four), S/PDIF coaxial and Toslink optical I/O, and one video/Word Clock input and six Word Clock outputs on BNC connectors. Big Ben provides a slot for an optional card to accept emerging formats; a FireWire I/O card ($695) will be available by year's end. An IEC receptacle rounds out the rear panel.
Big Ben's AES/EBU I/O supports both single- and double-wire formats and sampling rates up to 192 kHz (and as low as 44.1 kHz in single-wire mode). The S/PDIF co-ax jacks accommodate 44.1 to 192kHz rates. The Toslink optical connectors support S/PDIF optical, ADAT, S/MUX 2 and S/MUX 4 formats at up to 192kHz rate. Pull-up and pull-down rates are available when Big Ben is synched to its internal clock or an external video signal. Big Ben constantly sends digital black out all audio output jacks when the unit is slaved to its internal clock. When locked to an external clock that's embedded in a digital audio signal, Big Ben routes that signal (with clock) to all digital audio outputs and converts between AES/EBU, S/PDIF, optical and option-card formats.
Big Ben's internally terminated video/Word Clock input will accept either TTL Logic (Word Clock) or video black burst (PAL, NTSC or B&W) signals, depending on the unit's front-panel settings. Two of Big Ben's six Word Clock outputs can transmit a clock at fractions or multiples of the sampling rate; available rates include fs/4 (¼ times the sampling frequency), fs/2, fs ×1, fs ×2, fs ×4 and fs ×256. Intuitive front-panel controls make the selection of digital audio formats and clock rates a breeze. Also on the front panel are a series of LEDs that indicate whether each of the six Word Clock outputs sense over-termination or no termination on their slaved device. I found this feature to be somewhat a white elephant, however, when used with converters that don't comply with the 75-ohm termination standard.
Before I began any critical-listening tests, I knew my digital audio converters were performing much better when synched to Big Ben, because my recordings sounded extraordinarily warm and smooth. The acid test, however, was a blindfolded comparison of two A/D converter sets (Apogee Rosetta 96 and MOTU HD192) using various clocking schemes. For this test, I made multiple stereo recordings of acoustic guitar to Digital Performer with DPA 4011 mics and a Millennia HV-3D/8 preamp, and monitored the results through a Benchmark DAC-1, Hafler P3000 Trans•Nova power amp and D.A.S. Monitor-8 monitors.
The sonic differences between recordings made with the HD192 A/Ds when slaved to Big Ben's internal clock vs. using the HD192's internal clock were simply astounding. Big Ben's clock made the overall sound dramatically warmer (i.e., less edgy), the high end far sweeter and the spectral balance noticeably smoother. Trust me, this is not simply the ramblings of an obsessed engineer: Even my wife (who is not an audio person) could identify the recording made with Big Ben's clock!
Removing Big Ben from the equation for a moment, an A/B comparison of my Rosetta 96's converters to the HD192's A/Ds (with each converter set using its internal clock) revealed the Rosetta to be a bit warmer and smoother-sounding. The recording made with the HD192 slaved to Big Ben's internal clock, however, sounded a tad silkier in the highs (yet a little less open and flat, spectrally) than that made using the Rosetta (which necessarily was synched to its internal clock, as it does not have Word Clock input). Yet another A/B test revealed Big Ben's clock to be clearly superior to Rosetta's.
Big Ben is competitively priced at $1,495 list. This groundbreaking box gets my highest recommendation. You'll be amazed!
Apogee Electronics, 310/915-1000, www.apogeedigital.com.
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