home entertainment 2007

Before we begin…
A network music player is not a music
server. 2 The primary job of a music
server is to store digital music files and
distribute them elsewhere. A music
player facilitates the distant control of
these files, using the owner’s generalpurpose
WiFi network to wirelessly
2 The Roku SoundBridge can’t be called a music or
media server because it lacks an internal hard drive to
store music and/or video files, though its accompanying
software distributes files to other components for
playback. The owner of a digital music player must set
up the files of his music library on his computer’s hard
drive. Alternatively, a separate external hard drive, or
Network Attached Storage (NAS) drive—such as a
Maxtor Shared Storage (Plus) or a Buffalo Linksys—can
be used to store the music files. One attaches an NAS
to the WiFi’s router via an Ethernet cable. The drive’s
icon will then appear on the PC’s screen whenever the
owner pulls up the “My Network Places” page.
(fig.2). The noise floor is also much higher in level than is
usually found with 16-bit audio data. This is very poor
behavior. There is a slight peak evident at 60Hz in this
graph. Repeating the spectral analysis but with data representing
digital black gave the pair of traces shown in fig.3:
Fig.3 Roku SoundBridge M1001, 1 ⁄3-octave spectrum with noise and spuriae
of digital black, 16-bit data (right channel dashed).
Fig.4 Roku SoundBridge M1001, left-channel departure from linearity, 16bit
data (10dB/vertical div.).
ROKU SOUNDBRIDGE M1001
transport them from the music server’s
hard drive to an audio system. The
WiFi network allows the player to be
placed anywhere in the home.
The SoundBridge M1001 depends
either on iTunes or on free opensource
software, such as Windows
Media Connect or Slim Devices’
SlimServer, running on the musicserver
computer. Once this server
software is running, the SoundBridge
has many functions. Its large fluorescent
display shows track title, composer,
album name, or even real-time
spectral analysis.
Description
The SoundBridge M1001 comes in a
blister pack, along with a well-written
manual, a wall-wart power supply, a
remote control (two AAA batteries are
included), a 1 ⁄8" (3.5mm)-to-RCA cable,
and a detachable rubber base to steady
the cylindrical SoundBridge when it’s
placed on a flat surface. Its rear panel
has a socket for an Ethernet cable, a
separate area for a stereo line-level
jack, an RCA jack for the S/PDIF
coax, and a TosLink connector.
The player itself is a thin tube of
black and silver anodized aluminum.
Much of its front panel is taken up by
a fluorescent 200x150-pixel display
that runs almost the full 10" width of
the player. The SoundBridge has both
digital (coaxial and optical) and analog
outputs. Its audio circuitry includes a
proprietary 20-bit DAC to drive its
while the noisefloor is lower in level than in fig.2, powersupply–related
peaks can be seen at 60Hz and 180Hz,
and another peak of unknown origin is evident just below
60kHz.
Tying in with the amplitude error in fig.2, the Roku’s
plot of linearity error against absolute signal level is very
poor (fig.4). Not only do signals below –78dBFS suffer an
increasingly positive error, the DAC is “deaf” to signals
with a level of –75dBFS, hence the notch in the linearity
error trace at that level. Probably what is happening is
that a DAC code error is leading to frequency doubling at
that level, minimizing the fundamental’s energy in favor of
the second harmonic. (I had already returned the Sound-
Bridge to Larry Greenhill when I analyzed these test data,
otherwise I would have run more tests to confirm this
conjecture. I will do so in a “Follow-Up.”) Because of the
linearity error, the SoundBridge’s reproduction of an
undithered 1kHz tone at exactly –90.31dBFS reproduces
at a higher level than expected, but with what should be
just three clearly delineated DC voltage levels overlaid by
noise (fig.5).
Tested for conventional harmonic distortion, the
Fig.5 Roku SoundBridge M1001, waveform of undithered 1kHz sinewave
at –90.31dBFS, 16-bit data.
www.Stereophile.com, May 2007 69