Home Reviews Amazing Grace (m902 Review)

Amazing Grace (m902 Review)


There’s a long tradition of professional studio gear crossing over into the domestic market to become a firm favourite with hi-fi fans. Over the years no end of monitor loudspeakers have made the jump – the most famous being the BBC’s legendary LS3/5. The trend has not been quite so pronounced on the electronics side of the industry, until recently when the increasing prevalence of the standalone DAC and headphone amplifier saw a number of pro-gear manufacturers finding a ready market for their products amongst home audiophiles. One such company is the USA’s Grace Design, founded in 1994 by brothers Michael and Eben Grace. In the intervening years the company has built up an impressive range of clients including the New York Metropolitan Opera House, Skywalker Sound, Dolby Laboratories, Shure Microphones and even Stevie Wonder. But Grace first came to the serious attention of the audiophile fraternity in 2001 with the launch of its m901 model, one of the first commercially available 24/96 headphone amp/DACs on the market. That was updated to the 24/192- capable m902 in 2005 and followed by the m903 in 2011 which added a new asynchronous USB interface as well as both balanced and unbalanced outputs; it drew high praise from the hi-fi press and headphone enthusiasts.

Now the model has been upgraded again, this time to m920 status and in a nod to Grace Design’s pro-audio background is described as a ‘High Resolution Monitoring System’. Outwardly it looks little different to its predecessors, being a sturdily built, brushed aluminium unit, measuring 1.7in x 8.5in x 8.25in (H/W/D) and weighing in at a reassuringly solid 2.2kg. It’s inside, however, that the most significant changes have taken place. The Burr Brown digital to analogue convertors used in the m903 have been replaced by the latest ESS Sabre32 DAC – widely acknowledged as one of the best on the market at the moment.


As well as handling PCM files of up to 32bit/384kHz, the Sabre also allows for playback of both 64x and 128x DSD. It also features three userselectable filter options: fast, slow and minimum phase, so users can tailor the sound to their individual taste either for entire listening sessions or to suit individual music selections. Grace has also improved its proprietary s-Lock system, which is a dual-stage ‘phase lock loop’ circuit aimed at reducing jitter from non- USB digital sources. Other interesting features include a crossfeed option (dubbed xfeed) which subtly blends part of the right and left channel outputs together to better simulate the sensation of loudspeakers when listening through headphones – especially useful on recordings featuring hard-panned left/right stereo effects.

All the various functions are accessed via the busy front panel which features two headphone outputs, the power switch, input selector as well as a series of small LEDs to indicate incoming sample rate as well as the rotary volume control and a small but clear display panel. Holding down the volume control for three seconds and then turning it right or left gives access to the various menu options – although some of the symbols used can be a little cryptic so keeping the instruction book handy is pretty mandatory until you become familiar with the m920’s operation. A trio of small lights beneath the display indicate which output has been selected – headphones, line one, line two or both line one and two together. Round the back input connections include USB, unbalanced RCA, balanced XLRs and AES3 as well as digital coaxial and Toslink. Both unbalanced and balanced outputs are provided, although unusually the latter are on 1⁄4” TRS sockets which is either another nod to the m920’s pro-audio roots or simply because there wasn’t enough room for an extra set of the more common three-pin XLRs.


Right from the off the m920 comes across as a highly-resolving performer. Plugging in a pair of Oppo’s PM2 planar magnetic headphones, Dylan Howe’s ‘Subterranean’ had tremendous extension at both ends of the frequency spectrum. The Oppos can sound a little soft but the m920 seemed to brush this tendency aside to portray the music with masses of bite and detail. Howe’s delicate cymbal work positively shimmered with the right sense of brush hitting metal while bass was tight and punchy but never overpowering.

Playing Led Zeppelin’s ‘When The Levee Breaks’ there was a tremendous integrity to the music. This is a dense mix but the m920 pulled off the trick of letting the individual instruments have their own space without losing any of the bone-crushing power of the track. I’ve rarely heard John Bonham’s drumming sound as powerful through any headphone amplifier. Swapping the Oppos for a pair of ADL H128s the sense of detail remained, except the more forward nature of the latter headphones imbued the music with even more drive and tempo, showing the m920 is adept at highlighting differences between partnering equipment. As ever with ESS Sabre DACequipped components, changing between the three filter options does subtly alter the sound – although bear in mind the effect is dependent on the bit-rate and production quality of the material being played. I tended to gravitate towards minimum phase which seemed to give a slightly richer bass but opinions will vary.

Also, the xfeed feature was intriguing. Switched in it seemed to bring a wider soundstage, allowing the music to float a little more freely outside the headphones – although the overall mix sounded a little busier with perhaps not so much forensic detail. Using the m920 as a DAC/ preamp combination into the power amp section of a Creek Evolution 100A showed its talents are not confined to the headphone section alone.

The Clash’s ‘Bankrobber’ had focus to the vocals and instrumental backing, through the frequency range. Again the m920 was adept at highlighting detail yet never sounded sterile or overly mechanical in the manner of some DAC/preamp combinations. It also evinced excellent rhythm and timing thanks to a supple, agile feel that never let the music wallow. Part of this is down to its bass reproduction which was tonally rich and complex – and a world away from the one-box thump of lesser products. Playing ‘Passage To Hades’, Jah Wobble’s throbbing bass didn’t just underpin the music but wound sinuously around Evan Parker’s saxophone improvisations so both were operating as melodic counterpoints. And that’s what the m920 does so well – simply play music superbly, whether as a supremely confident headphone amplifier via either analogue or digital inputs or as a DAC/preamp feeding a good power amplifier. As such it’s capable of forming the heart of a very good system indeed.


It may look a little utilitarian but the sound the m920 produces is anything but. This is a rich, detailed and musical headphone amp/DAC and preamp combination that bears comparison to some of the best on the market. Recommended without reservation.


The Grace m920 had a gain of x3 (dB) from its analogue Line input to the headphone output sockets, and no less than 5.8V was available for headphones where most need 1V-2V, so there is
plenty to spare. Curiously, there was slight attenuation of x0.8 from XLR input to headphone output. Both inputs were wideband, with an upper limit beyond 80kHz, and low distortion (0.001% at 1V out).

All three S/PDIF digital input – AES/EBU, Optical (Tos) and Electrical – processed a 192kHz sample rate signal; no limitation was imposed by the optical receiver. Frequency response extended to 60kHz (-1dB) before slowly rolling away to the 96kHz upper limit, our analysis shows. Distortion from 16bit (i.e. CD) measured 0.21% at -60dB, and with 24bit resolution 0.03% – both low
values. However, some quantisation noise products existed close to the fundamental and these limited EIAJ Dynamic Range to 116dB via Optical and Electrical, and 117dB via AES/EBU, where the Sabre32 is specified as and usually manages 123dB.

The USB input processes 96kHz sample rate maximum, below 192kHz or 384kHz now being achieved. Frequency response measured flat to 46kHz (-1dB) and a full level signal (0dB) provided full
5.8V output from the headphone socket. Distortion at -60dB measured 0.09% and EIAJ Dynamic Range was 115dB, just 1dB below S/PDIF due to a little noise. This isn’t very consequential however. The m920 measured well and reaches high standards. However, it doesn’t get the best from the Sabre32 DAC that can manage 6dB more dynamic range.

Frequency response (-1dB) 4Hz-60kHz

0dB 0.0008%
-60dB 0.03%
Separation (1kHz) 96dB
Noise (IEC A) -115dB
Dynamic range 116dB
Output (headphone) 5.8V


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