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Overview of 518 7
518 User Guide
Planning setup of 518
Firstly, the 518 is a product for enthusiasts! We designed it for audio and
multimedia enthusiasts, keen listeners and those with enthusiasm for the
best sound.
However, 518 is something of a chameleon. What do we mean by that?
This is best explained by seeing what it does: 518 fulfils four very different
functions in one box.
We have categorised uses (applications) of 518 into four broad headings,
as follows:
• A simple 'preamp' or Control Unit for a purist digital audio system.
(Type 0) – see below.
• A Resolution Enhancement processor in a high-quality audio system.
(Type 1) – see the overviews on pages 10 and 49.
• A Mastering Processor, used in any recording, editing, mastering or
dubbing process. (Type 2) – see the overview on page 12.
• A peri-computer Multimedia Processor. (Type 2) – see the overview
on page 12.
What's inside a 518?
Input Switch Twin PLL 42MHz DSP Digital Output
Front Panel
Control
Computer
D1
D3
RS232
D2
Out
Internal block diagram for 518
Opt
518 is a 2-channel digital audio computer with four inputs – see the
diagram above. The selected input is de-jittered with a proprietary
Meridian twin phase-lock-loop that acts as a 'big flywheel' to regulate the
audio stream. By using this twin PLL we ensure that the outgoing digital
audio has very precise timing allowing the final output device (e.g. DAC)
to achieve its maximum sonic potential.
1
Following the twin PLL is a fast (42MHz) 24-bit Digital Signal Processor,
which runs the user programs in 518. The DSP functions are all controlled
by an internal computer which co-ordinates the front-panel keys, remote
control sensor and display as well as RS232 control.
All software for 518 – control and DSP is held in a socketed EPROM. This
allows the potential of upgrades or new applications being issued later.
Following the DSP is a multistandard digital output.
1
For the technically interested, Figure 1 on page 49 shows the
performance of the twin PLL.