Recording - November 2017 - 36

Grace Design
m900 Headphone
Amplifier
The beloved Grace sound-
anywhere, anytime
REVIEW BY MIKE METLAY

race Design, located in the lovely mountain town of Lyons,
Colorado, is a pro audio manufacturing company
owned and run by the brothers Eben and Michael
Grace. While there are several other companies that offer
gear that's "straight wire with gain," Grace Design's preamps
and monitoring devices always seem to provide that with just a
certain something that keeps them from becoming clinical. It's
an approach that's made a lot of fans, myself included.
I've reviewed a couple of Grace Design's headphone amplifiers
over the years, most recently the m903 in January 2013 (now
superseded by the m920) and the m905 in March 2014. Both
of my reviews ended with essentially the same sentiment: "I love
the sound of this box, and you will too... if you can make the
investment it requires." These are fantastic products, but they're
not cheap... and for many users, they offer a huge slate of
features that will be rarely if ever used.
As I sadly returned both reviewed units to les frères Grace, I
found myself wishing more than once that Grace Design would
do something for headphone monitoring that was roughly equivalent to the company's fabulous m101 preamp: a basic listening
system that provides the Grace sound with minimal features, all
at a price that even folks in very small studios could afford.
It looks like I've finally found the right star to wish upon.
Allow me to present the very compact, very affordable, and
very amazing Grace Design m900.

The little black box

The m900 is a 2-channel D/A converter and headphone
amplifier with a surprising number of extras under the hood.
The 4 x 5.25 x 1.8 inch solid metal box has a good heft to it,
but isn't so heavy that you'd want to leave it at home. Its most
notable features are a smooth and lightly-stepped volume control encoder on the top and a bright dual-digit LED display on
the front. The front edge also has two 1/4" TRS headphone jacks
that run in parallel.
On the rear panel you'll find unbalanced RCA outputs to run an
external set of speakers, a coaxial S/PDIF input, and an optical
36

RECORDING November 2017

Toslink input (to use the m900 as a D/A without a computer).
There are two USB Micro-B ports, one for a computer connection
and the other for an included 2 Amp power supply.
This extra power supply isn't always needed; the m900 will
run happily in Low Power Mode using bus power from a connected
computer (or a conventional 0.5 Amp power supply, as on an
iPad charger, if for some reason you don't have the 2A power
supply with you). Connecting the 2A supply does two things.
First, it lets the m900 run in High Power Mode, which provides
a bit more oomph for headphones that are harder to drive
effectively, like older 600Ω designs and the planar magnetic
phones favored by some audiophiles. Second, it lets you hook
up iOS and Android devices via the appropriate cables or
adapters (the m900 calls this Self Powered Mode).

Under the hood

In normal operation, the LED display shows the output level
in dB, from 0 to 99 dB, in 0.5 dB increments (a decimal point
indicates "plus a half"). The level encoder can be push-clicked to
mute the outputs. This level control affects both headphone jacks
and the line outputs; note that the right headphone jack switches
off the line outputs when a pair of headphones are plugged in.
If the encoder is pressed and held for two seconds, the m900
enters Setup Mode. This is where you set things like the default
power-up volume, whether the display turns off after a few
seconds, which input the m900 should be listening to (USB,
Toslink, or coaxial S/PDIF), and a few functions that deserve a
bit more description...
First off, there's sample rate display (not selection; the m900
reads the input signal and adjusts to it). The m900 effortlessly
handles up to 32-bit audio, at sample rates from 44.1 kHz to
an in-bloody-sane 384 kHz, as well as three quality levels of
DSD audio (64, 128, and 256). If you like listening to DSD files
and want to use your computer rather than a hardware SACD
player, this alone is worth the cost of the m900.
Then there's USB Audio Class selection. Long story short: USB
Audio Class 1 supports up to 96 kHz operation on macOS and
Windows without special drivers. The newer USB Audio Class 2
is still driverless on macOS, but requires a driver download from
the Grace Design website for any version of Windows before
the recent Windows 10 Creators Update. In Class 2, sample
rates up to 384 kHz are supported.
Crossfeed is a feature that's common to every Grace Design
headphone product. This all-analog process loosely simulates the
acoustics of listening to speakers in a room by feeding each ear a

Table of Contents for the Digital Edition of Recording - November 2017