The Fifth Element #69 Page 2
What makes asynchronous conversion desirable is that it reverses the usual master-slave relationship in which the computer's internal clock dictates the timing of the digital-audio signal. In asynchronous mode, it is the clock in the USB DAC that is the master, and the computer the slave. The reason this makes a difference is that the computer's own clock has other tasks to perform, which makes for more jitter. Asynchronous implementation also means that sample-rate conversion and phase-locked loops are not necessary. Technical explanations aside, asynchronous USB simply sounds better, at least in my experience. The m903 uses a miniature USB jack, and so Grace thoughtfully provides a cable with a full-sized USB plug on one end and a mini-plug on the other; this was the only USB cable I used.
A few other nifty things about the m903: It has balanced and single-ended analog inputs on XLR and RCA jacks. When an analog input is selected, the m903's digital circuits power down. This is just one example of how thoroughly thought-through this design is. Another example is the Menu's Mono setting, which the owner's manual recommends you use to listen to early Beatles recordings.
The m903 has two headphone jacks; these are wired in parallel, so the volume control controls both together. There are two sets of line-level analog outputs: L1 is single-ended on RCA jacks, while L2 is balanced on ¼-inch TRS jacks. The levels for the headphone jacks and the two line-level outputs are independently controllable. Which output is being controlled is determined by sequentially pressing the volume knob, and indicator lights on the front panel show which input is under control: the headphone jacks can be at one level, L1 at a different level, and L2 at a third level. However, by using the setup menu, which is called up by pressing in and holding the volume knob, it's possible to gang L1 and L2 together. This means that the m903 can control a satellites-and-subwoofer systemwhich many professional and prosumer monitoring setups are.
That volume knob is a "smart" knob with a three-stage acceleration curve in increments of 0.5, 2.0, and 4.0dB. The m902 had a menu function to set all analog outputs to Hi or Lo. This has been replaced in the m903 by a function that can independently master-adjust the levels of the three outputs over a range of ±9.5dB.
For the digital inputs other than USB, the m903 employs a proprietary phase-locked loop that Grace calls s-Lock. This locks to the incoming clock, and once lock is achieved (as indicated by a front-panel LED), the m903 runs off its own internal clock. The m903 can lock to an incoming signal within a range of ±5Hz at 44.1kHz. However, if lock is not achieved, the m903 will nonetheless play in most cases, with claimed "excellent" recovered-clock jitter performance (though this will largely be determined by the quality of the source device). In USB mode, the m903's system clock is the master clock to which the computer is synced, and so s-Lock is inactive.
I did, of course, listen to the Grace m903 with headphones, but mostly I used it as I think most audiophiles will: as a DAC in a system. Mine comprised Vivid Audio's B-1 and K-1 loudspeakers, Cardas Clear speaker cables and single-ended interconnects, Luxman's C-600f solid-state power amplifier and surprisingly powerful MQ-88 tubed power amp, Ayre's CX-7eMP CD player as an AES/EBU digital transport, Meridian Sooloos's Control:15 as an S/PDIF source, and my iMac computer as a USB source. My headphones were Audio-Technica's cheap'n'cheerful closed-back M50s ($199, reviewed in the February 2010 issue) and, briefly, the 600-ohm variant of Beyerdynamic's wonderful DT 770 Premium closed-back model ($269). (Medium- and low-impedance models are also offered for use with portable music players, but I found the sound of the high-impedance version slightly more appealing. More in a future column.)
First crack off the bat, I connected the m903 to my iMac and listened via Amarra (I still can't get over how much better it sounds than iTunes) to HDtracks' 192kHz download of Bill Evans' "My Foolish Heart," from Waltz for Debbie, using the Beyerdynamic DT 770s. Wowzers. A night-and-day difference from Grace's previous USB (1.0) sound. I quickly cued up my AIFF "Red Book" file of the same track, but from The Complete Village Vanguard Recordings, and while it was nowhere near as immediate, it was still very, very good.
Whether via USB, S/PDIF, or AES/EBU, the m903 carried on the Grace tradition of (to quote Sam Tellig) "warm, rich, and full-bodied," easy-to-listen-to sound, but definitely took it up another notch in every respect, especially in that intangible called "sophistication." I expected the USB performance to be much better, and found it outstanding. However, I was not prepared for how much better the S/PDIF and AES/EBU performance was in terms of resolution of musical details and overall involvement. Still, taking into account changes or improvements in the DAC, the amplifier, the power supply, and the volume control, I probably shouldn't have been surprised. The m903's USB performance was at least as good as S/PDIF or AES/EBU; indeed, Joni Mitchell's piano and voice in Court and Spark's title track seemed almost imperceptibly richer through the USB input.
A visitor who listened to the m903 made an interesting comment. He said that the m903 handled the music so gently that it was the first DAC he'd heard that he'd be tempted to describe as "feminine." I think that's a large part of its charm. However, most virtues have flip sides. In a direct comparison with the $5500 combination of Antelope's Zodiac Gold D/A headphone amp and its optional Voltikus power supply that I wrote about in October, the Antelope started and stopped faster (like a wildebeest?), and had punchier dynamics. For my own tastes, I put timbre ahead of dynamics, so I'm not bothered by this. But if "slam" is what you're looking for, perhaps the Grace m903 is not the DAC for you.
The Grace Design m903 continues the tradition set by its predecessors by being "a great, high-resolution DAC in a very cost-effective package" that offers remarkable clarity, continuity, and roundness of tone, and is better in almost every way than the m902. Major performance gains with only a $200 increase in price, and still made in good ol' Colorado. Those looking to upgrade their CD player or music server should check out the m903. Highly recommended.
Great Cheap Headphones
If you like to listen to your iPod while doing yard work, such as using a leaf blower, have I got a pair of headphones for you! For the ridiculously low price of $36, industrial-safety company Howard Leight offers (on amazon.com, as well as elsewhere) the Sync: passively noise-isolating headphones. I compared them to my Audio-Technica ATH-M50s, and the Syncs held their own to a surprising extent, and really did isolate (to a claimed 25dB) outside noise. They fit me just fine, but common sense should suggest that their noise-reducing function depends on their sealed earcups making a very tight sealI wouldn't want to wear them all day. But over and above yard work, these should also serve very well as affordable isolation headphones for garage bands, basement recordists, or drummers. The cord detaches from the left earcup, so they can also be used as hearing protectors only. Neat!
Running out of space here, so must be brief. I really like Arcam's rDAC ($479)a stripped-down, basic product with an interesting "unique selling proposition." For the rDAC, Arcam licensed asynchronous USB technology from ultra-premium digital engineers dCS, which makes the rDAC, as far as I know, the least-expensive DAC with asynchronous USB. The size of a paperback thriller, the rDAC has elegant industrial design and a resilient, rubber-like bottom that keeps it from sliding around on your desk, and which is claimed to damp vibrations. It has S/PDIF, optical, and USB inputs only. Its DAC is a Wolfson Microelectronics 8741again, a hi-zoot component that's a pleasant surprise to find in such an affordable product. The rDAC can handle 24-bit/192kHz via S/PDIF, but USB is limited to 24/96. (There is a wireless version, but I prefer wired versions.) It uses a wall-plug 6V power supply.
Over the past several months the rDAC has been in and out of my system, and has never sounded anything other than very listenable and very musical for something that costs $479. In short, I would rather listen to it than to Musical Fidelity's $699 M1DACthe rDAC had more air and detail and sounded a bit livelier. While not as revealing as the Grace m903, the rDAC's timbral balance was similar: warm and a bit rounded, though perhaps slightly leaner than the Grace's. The rDAC couldn't unravel musical layers or present soundstage depth the way the Grace can, and just forget about comparisons to the Bricasti M1 DAC that I reviewed last October. The synth strings in "So Do I," from Christy Moore's This Is the Day (CD, Columbia Sony Music 5-3225.2), were on the same plane as everything else via the rDAC; via the order-of-magnitude more expensive Bricasti, they were layered (footnote 2). The rDAC's USB performance was at least as good from USB as from S/PDIF, and perhaps USB was slightly more dimensional and lively, even with iTunes; with Amarra, the differences were more pronounced.
The only thing that might keep people shopping in the rDAC's price tier from closing the sale is that the rDAC is only a DAC; it's not a headphone amp. I can understand the logic behind such a design decision. I think the rDAC is aimed at people who want to get better sound out of their stereo systems while playing music stored on a computer or a Squeezebox or Sonos system. And doing a headphone amp "right" is neither easy nor cheap.
To sum up: handsome styling, great USB performance, sonic defects that are sins of omission rather than commission, and unfailingly musical and listenable; just not the last word in resolving powerand for $479, you shouldn't expect it to be. Recommended.
A few gift recommendations: They Came to Play on DVD, which I wrote about in April 2011; Light & Gold (CD, Decca 001485002) a new recording of Eric Whitacre conducting his own choral works; and Shunyata Research's cryogenically treated SR-Z1 wall outlet ($75). Peace!
Footnote 2: Plaudits to Moore for using a synth. I just hate it when four rapacious conservatory-graduate string players beat one keyboard player out of a gig.