Meridian G91 Installation Manual page 8

4
I n t r o d u c t i o n
a received signal. There is also a DSP-based low-pass filter and a
whistle filter for improved AM reception.
Upsampling
The G91 provides upsampling, which allows filtering to take place
far beyond the range of human hearing, as well as offering other
audible benefits right across the audio band, including improved
transient response. All processing is 48-bit precision. This results in
a more open, transparent sound, tighter bass, and a generally more
'musical' sound overall.
To drive the analogue outputs, signals are upsampled to 176.4/
192kHz for digital to analogue conversion – DACs can offer better
performance at higher sampling rates – and 88.2/96kHz is used for
the digital outputs, all at 24-bit word lengths.
Here again, sending 24 bits at high sample rates via an S/PDIF link
reduces jitter as compared with the original 44.1kHz, 16-bit signal
from a CD, for example. In addition, digital outputs derived from
high resolution sources are encrypted, removing cyclic components
from the data stream and again reducing jitter.
All these advanced digital processing features are handled by a
powerful DSP engine delivering an impressive 150MIPS (million
instructions per second).
Digital surround processing
In addition, the G91 incorporates digital signal processing to allow
the multichannel digital output and stereo analogue output to
be used to directly drive a basic 5.1 surround system based on
Meridian DSP loudspeakers and up to two analogue speakers (left
and right, centre, subwoofer, centre and subwoofer, or rear left and
right).
A setup option allows you to define the configuration of
loudspeakers in the layout, and specify whether the bass is handled
by a subwoofer, or the speakers in the layout with good bass
handling. A separate Calibration page allows you to calibrate
the layout by adjusting the gain and distance of each loudspeaker,
while listening to test signals. This lets you fine tune the layout for
an optimum surround image.
The built-in surround processing decodes 5.1 Dolby Digital or DTS
soundtracks from DVD-A or DVD-V discs, or from the external
digital inputs. It will also create a full surround image from two-
channel soundtracks on audio CDs, DVD-A or DVD-V discs, or from
the external two-channel digital or analogue inputs.
Several DSP presets are provided to allow you to choose the type
of surround processing. For 5.1 audio formats a Discrete or Cinema
DSP preset is selected automatically, depending on whether the
source is music or a movie. For two-channel audio formats the DSP
preset can usually be switched between Trifield (recommended
for music), Stereo (uses just the main left and right speakers and
subwoofer), or PLII (recommended for movies), using the DSP key
on the front panel or MSR+.
The default preset is Trifield for audio CDs, two-channel DVD-As,
the internal tuner, or a two-channel external input, and PLII for
two-channel DVD soundtracks or a two-channel Dolby Digital