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Introduction
The 861 Reference Digital Surround Controller
Digital signal processing, or DSP, is a technique
pioneered by Meridian in hi-fi products for achieving
extremely accurate reproduction of audio signals.
Unlike conventional analogue systems – which process
signals using electronic circuits based on resistors,
capacitors, and inductors – DSP works by performing
exact mathematical calculations on digital versions of
the signals.
The advantage of DSP over analogue circuitry is that
the signals are held as precise numbers, rather than
voltages in a circuit. This means that any number
of stages of processing can be performed with high
precision, and without any of the cumulative noise or
degradation that inevitably occurs, even with high-
quality analogue circuitry. In addition, several of the
surround-sound decoding techniques and signal
improvement techniques available in the 861 would be
virtually impossible to implement in analogue circuitry.
At Meridian we have taken advantage of the availability
of high speed DSP microprocessors to incorporate
DSP in hi-fi products, and the 861 is the result of over
a decade of our research and development in this field.
The 861 takes advantage of DSP for several different
functions:
To de-jitter incoming digital signals and expand the
precision of the signal.
To perform filtering or adjustment of the frequency
response; eg treble or bass.
To decode digitally-encoded signals from Dolby
Digital (AC-3), DTS, or MPEG Audio.
To process the audio into a multichannel signal, and
match the source channels to the configuration of
main loudspeakers and subwoofers in the system.
The 861 converts analogue input signals to digital
format, using high-quality analogue-to-digital converters
(ADCs). Digital signals, from CD, DVD, or digital
broadcasting, are already in digital format and do not
need to be converted.
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The signals are then retained in digital form throughout
the 861 until they are converted back to analogue
form at the analogue outputs, to drive power
amplifiers. If you are using the 861 with Meridian DSP
Loudspeakers, the signals remain in digital form until
the last possible stage.
The architecture of the 861 allows for wide flexibility
– future sources and formats can be handled by
upgrading either software or cards.
Meridian MHR Smartlink and MMHR
The 861 Reference Digital Surround Controller
incorporates the unique MHR SmartLink and MMHR
multichannel links. The MHR SmartLink allows it to
receive an upsampled 6-channel PCM stream from a
compatible source such as the Meridian 800 Reference
DVD/CD Player. The MMHR receives an 8-channel
PCM stream from a compatible system such as the
Meridian HD621 HDMI Audio Processor.
Meridian MHR Smartlink and Meridian MMHR obtain
intelligent stream content information from the source,
allowing the 861 Reference Digital Surround Controller
to select an appropriate preset depending on whether
the source is music or a movie soundtrack, and
whether it is 2-channel or multichannel.
Inputs
The 861 is a full-system controller preamp that
provides seamless control of up to 12 sources.
By providing digital as well as analogue inputs the 861
can give radically higher sound quality for sources that
are originally digital – like CD, Digital Radio and DVD.
As well as accepting 2-channel or multichannel
digital audio, the 861 will handle SPDIF-encoded
Dolby Digital, DTS, or MPEG from sources like DVD,
Satellite, and BluRay.