Grace Design m902 Reference D/A headphone amplifier Sam Tellig, October 2008

Sam Tellig wrote about the m902 in October 2008 (Vol.31 No.10):

John Atkinson and Wes Phillips reviewed the Grace Design m902 Reference in April 2006, and since then it's remained essentially unchanged.

As standard, for $1695, the Grace m902 offers four digital inputs—RCA/S/PDIF, TosLink optical, USB, and AES3—plus two pair of analog inputs (unbalanced RCA, balanced XLR). The analog output is a pair of unbalanced RCAs—or, for $1850, you can have a pair of ¼" TRS balanced outputs instead. An additional $125 puts into your hands a beautifully machined remote control—an option that's really a necessity, but isn't available with the Benchmark DAC1 Pre. For everything—balanced TRS outputs and the remote—you're looking at $1975.

Once the Grace is connected via a USB input, your PC or Mac should recognize it. I had no problem with my Mac mini running OS X10.3.9, using Audio MIDI setup to select "USB audio device" as the default output.

Ergonomically, the Grace Design m902 is a joy. There's that remote control. It's a pure joy for this geezer not to have to jump out of his chair to tame or turn up the volume. There are separate output-level controls for the line stage and the pair of headphone jacks. Moreover, the gain level can be adjusted from the front panel's digital display without opening the case and fussing with internal jumpers.

The m902 also features something called cross-feed circuitry, which Grace calls X-Feed. This option (accessible via the front panel or the remote) mixes some of the right-channel signal with the left, and vice versa. The aim is to create a more realistic soundstage, enhance localization, and eliminate some listening fatigue due to your ears' struggle to make a recording sound real. Its effects are subtle, but on the whole welcome for headphone listening. It's one of those things that you may notice is off when it's off and then want to turn back on—a breeze from the remote. This feature is found in headphone amps from HeadRoom, but I haven't seen it elsewhere.

The fit and finish of the m902 Reference are exquisite. The beautifully machined case has the look and feel of something twice as expensive. It's the kind of equipment you want to caress. Hi-fi hardware porn. Capitalist luxury at a proletarian price. Comrades! To the barricades!

Yes, the remote control does add $125, but it's a far cry from the cheesy plastic remote controls you sometimes see even with expensive gear. Like the m902 itself, the remote (made for Jeff Rowland Design Group) exudes quality and hints of longevity in a throwaway world.

Does it pay any longer to buy an expensive CD player? Did it ever? You know what's likely to crap out first: the transport mechanism. Good luck getting it fixed. In some cases, good luck finding the manufacturer or importer. Why not keep the player(s) you have now and invest in a good DAC, since the quality of the transport may not matter so much anymore?

Overall, the Grace Design m902 Reference has a warm, rich, full-bodied sound that reminds me of gear from Jeff Rowland Design Group. (Perhaps this should be no surprise; Michael Grace, founder of Grace Design, used to work for Rowland, and both companies are based in Colorado.)

The sound was anything but analytical or clinical, which reflects the way Michael Grace says he approaches digital: with an ear toward avoiding listening fatigue for his pro-audio customers, who must listen through headphones all day long. The sound was reminiscent of tubed gear in its smoothness and roundness, but not quite. It didn't matter which digital input I used, or whether I used the Cary CDP1's DAC (via the Grace's analog inputs) or the Grace's own internal DAC.

As a line stage, the Grace Design m902 seemed to have more character than the Benchmark DAC1 Pre. Not that I'm beefing about the Benchmark. The Grace may have had more muscle and musicality, too. It seemed to me more like a standalone line stage than the Benchmark. (By the way, the Grace m902 has a balance control, accessible from the front panel or from the remote. The Benchmark does not.)

Whether using its own internal DAC or that of the Cary CDP1 CD player, the Grace m902 had a way of fleshing out the tonal qualities of voices and musical instruments. This made it one of my favorite headphone amps, too—maybe even my top fave. I experienced no listening fatigue.

Like the Benchmark DAC1 Pre, the m902 Reference is probably not fussy about whatever transport you use. Its proprietary s-Lock phase-lock-loop (PPL) system is designed to capture the incoming clock from the chosen digital input and switch it to the s-Lock clock to run the DACs, which are Burr-Brown PCM 1730s.

"The PCM 1730's current output and this allow us to build our own transimpedance amp for current-to-voltage conversion," Michael Grace told me. (The usual, cheaper approach is to turn current to voltage via a voltage-feedback op-amp.) "The way current-to-voltage conversion is handled determines the characteristics of the sound," he continued. "Current-feedback amplifiers have a low-impedance current input and so don't have slew-rate limitation issues with instantaneous changes in the current coming into the amp. Voltage-feedback amplifiers, by contrast, constantly operate in a nonlinear way when they're used for current-to-voltage conversion. As a result, transimpedance amplifiers have a more open, harmonically rich and detailed sound.

"No single design concept accounts for the [m902's] sound," said Michael. "For instance, we don't like electrolytic capacitors, preferring polymer film capacitors anywhere possible in the signal path. The headphone amplifier itself is an Analog Devices DSL transimpedance driver capable of very high current output. It can drive a signal from a modem in your home or office, via a twisted pair of wire, a mile or two to the phone company, and can deal with high amounts of capacitance and reactance. Because it has no slew-rate limitations, it can track the rich harmonic content and overtones of the music in a way that a regular amplifier can't."

That's what you need to drive your headphones—and your power amp: a DSL modem!

I think you'd find the Grace Design m902 Reference a big upgrade from most CD players—or outboard DACs, for that matter. While I did hear a little more air and openness when I used the Cary CDP1 CD player through the Grace's analog inputs instead of the Grace's onboard DAC, I don't want to make too much of this.

I was, however, slightly disappointed with Internet radio from my Mac mini via the Grace's USB input. Compared to the Benchmark and the Ray Samuels Predator, I noticed a more pronounced lack of openness and airiness. The sound wasn't edgy or offensive, just slightly lifeless and dull. Perhaps Grace could take another USB approach.

I could easily live with the Grace m902, though I still haven't decided whether or not to buy it. So beautifully made. So musical. It has soul. Humanity. There but for the Grace named Michael goes thin audiophile sound.

What might make the Grace Design m902 Reference a must-have for me is that remote control. Every headphone amp should offer this feature, but few others, if any, do, and I'll tell you why: Because audiophiles must suffer.

Tyll Hertsens, of HeadRoom, calls the Grace a "bad boy" headphone amp. He means it in a good way. Along with its musicality, the m902 gets a superb grip on demanding headphones such as AKG's K-701.

As they say in Russian, Molodyets! Good job, Grace Design!

Grace Design
2434 30th Street
Boulder, CO 80301
(303) 443-7454