Audio Research Reference CD9 CD player/DAC
Now entering its fourth decade, the Compact Disc player seems to have reached a stage of maturity where the best models within a given price range will sound pretty much alike. The technology of the Compact Disc itself is set, its possibilities and limitations are well understood; and the designers of CD players who figure out how to stretch the former and finesse the latter wind up at about the same sonic place (again, for the same price), even if they've taken different routes to get there. What distinguishes these players in the marketplace tends to be not so much their sound quality as their features, and the world of digital audio has expanded in ways that make features very importantsome of them, anyway.
And so we have the Audio Research Corporation's Reference CD9 digital-to-analog converter and CD player, which, at $12,999, costs about the same as my Krell Cipher SACD/CD player ($12,000), but is so different in design and function that it offers a good test of my theory on converging sound qualities. In the May 2012 issue, I called the Cipher "a great CD player: the best I've heard in its price range, and the best I've heard, period, in my home system." How does the Reference CD9 stack up? What can each player do that the other can't, and does it matter? What does the very existence of such machines, near the peak price for a single-chassis player, say about the future of high-end audio?
The Reference CD9 is a top-loading player that uses Philips's CD Pro2 transport. The drive rests on a ½"-thick metal I-beam that extends the player's full depth. Four 6H30 dual-triode tubes drive the analog section; a fifth 6H30 and a 6550C regulate the power supply. ARC claims that its use of four digital-to-analog converters (two per channel, each in dual-mono mode) reduces the digital noise floor by 3dB (ie, doubling the number of DACs doubles the signal's amplitude while keeping the noise the same). Power is handled by a custom transformer that, according to design engineer Dennis Petrich, has no gaps or breaks in the material of its R-core and thus more efficiently contains the flux field, with much less leakage, resulting in less distortion and a higher signal/noise ratio. Jitter reduction (to <10 picoseconds, according to the spec sheet) is handled by a crystal-controlled reclocking mechanism.
In its most up-to-date feature, the CD9's rear panel has not only digital outputs but also five digital inputsS/PDIF on RCA, BNC, and TosLink, AES/EBU on XLR, and USBfor outboard digital devices or digital streaming. (The player comes with a CD-R carrying the necessary driver programs for Macs and Windows PCs.) Once you've pushed a button (on the CD9's front panel or its remote control) that activates one of these digital inputs, you can set the bit rate to 24 and the sampling rate to 44.1, 88.2, 96, or 192kHz, depending on the source signal. (You can also set it to play at the source's native resolution, whatever that may be.) The DACs are also equipped with dual oscillators, so that music at 44.1kHz (or doubled to 88.2kHz or, from there, to 176.4kHz) uses one of the oscillators, while music played at 96 or 192kHz uses the other.
Finally, when you're spinning discs, the CD9 allows you, with a push of a button, to upconvert the sampling rate from 44.1 to 88.2kHz. Another button lets you select the digital filter: Fast (a brick-wall filter at the highest frequency) or Slow (a filter with a more gradual rolloff).
For those familiar with Audio Research CD players, the Reference CD9 is the same as the CD8 (released in 2010 at a price of $9995), except for its digital inputs, the selectable filters and upsampling options, and the circuitry that facilitates them: the four DACs (vs the CD8's two), the two master oscillators (vs the CD8's one), the greater bandwidth of the analog circuitry, and the sample-rate display on the front panel.
I hooked up the Reference CD9 to a system that included the Simaudio Moon Evolution 700i integrated amp, Revel Ultima Studio2 speakers, and Nirvana cables. I usually place Black Diamond Mk.4 Racing Cones under all electronic components and plug all hi-fi gear (except amps) into a Bybee Technologies Signature Model Power Purifier. But David Gordon of Audio Research urged me not to do this, at least at the outset, so I let the CD9 stand on its own Sorbothane feet and plugged its power cord straight into the wallin my case, into hospital-grade sockets wired to a dedicated 20-amp circuit. He was right: the player sounded a little better without the usual aids.
I played lots of CDs, occasionally pushing the buttons on the remote control to switch between straight 44.1kHz and the same datastream upsampled to 88.2kHz, and from the Fast (brickwall) to the Slow (gradual rolloff) filters. (About my findings on these matters, more later.) ARC recommends 600 hours of break-in; I gave the review sample three weeks of continuous play before settling down to serious listening. I conducted several A/B comparisons with the Krell Cipher. To check out the CD9's digital inputs, David Chesky, of Chesky Records and HDtracks, brought over a MacBook Pro and an external hard drive loaded with Audirvana software and lots of high-resolution tunes from the Chesky catalog (mainly in 24/192, but a few in 24/96), which I compared with CDs and, when possible, LPs of the same titles.
As a CD player, the Reference CD9 was simply excellent. This wasn't a surprise, given Audio Research's track record. What was a surpriseand what takes me back to the proposition at the top of the reviewis that it sounded almost exactly like the Krell Cipher, even though the Cipher has a front-loading transport (it's not a top-loader), transistors (not tubes), two DACs (not four), and proprietary circuitry that manipulates audio signals in the current domain (not the voltage domain). Often, two similarly high-priced components may both "sound good" but have different strengths and weaknesses, which in many cases stem from their designers' different preferences or trade-offs. A review that compares two such models generally identifies those trade-offs, weighs the differences, and concludes which player might be better or worse for various kinds of music or taste. Usually, the differences are pretty clear.