Meridian America DJ Equipment Meridian 518 User Manual

MERIDIAN 518 USER MANUAL  
© 1992, 1993, 1995  
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3
Simple rules for using 518..................40  
Additional technical information.........42  
Specification.........................................42  
Help!......................................................43  
Appendix 2 – Hints on Mastering  
with noise-shaping ......................... 47  
Appendix 3 – RS232............................. 49  
Appendix 4 –Resolution  
Enhancement .................................. 50  
Standby point not lit ...........................43  
Audible hiss at high volume  
settings.........................................43  
No output with Meridian 565,  
DSP speaker or DAC....................43  
No time display with Meridian  
DSP speaker ................................43  
Communications not working  
Jitter and de-jittering.......................... 50  
Dynamic-range.................................. 51  
Dynamic-range optimisation  
with Gain...................................... 52  
Dynamic-range optimisation  
with Pre-emphasis........................ 52  
Dynamic-range optimisation  
with Noise-shaped Dither ............. 54  
DAC enhancement by using  
between 518 and other  
Meridian products. ........................43  
Radio interference .............................43  
high-frequency dither.................... 55  
DAC or channel enhancement  
Cleaning................................................44  
Maintenance & Service.........................44  
Part 3.....................................................45  
Appendix 1 – Noise Shapes.................45  
by word-length matching .............. 55  
Index..................................................... 56  
Notes..................................................... 58  
518 User Guide  
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4
Sales and service in the UK  
Meridian Audio Ltd  
Stonehill  
Huntingdon  
Cambs. PE18 6ED  
England  
Tel (0) 480 52144  
Fax (0) 480 459934  
Sales and service in the USA  
Meridian America Inc.  
3800 Camp Creek Parkway  
Building 2400, Suite 112  
Atlanta, GA 30331  
Tel. (404) 344-7111  
Fax (404) 346-7111  
Designed & manufactured in the UK by  
Digital Gramophone & Wireless Ltd  
Stonehill  
Huntingdon  
Cambs. PE18 6ED  
England  
Copyright © 1992,1993,1995 Digital Gramophone & Wireless Ltd  
Acknowledgements  
Trademarks etc.  
Boothroyd|Stuart Meridian and Meridian are registered trademarks of  
Meridian Audio Ltd.  
Super Bit-Mapping is a trademark of Sony Corp.  
Testers  
The processing in 518 has been beta tested in a 618 version over some  
three years. Thanks in particular to Tony Faulkner (Green Room  
Productions), David Chesky (Chesky Records), Tom Jung (DMP  
Recording), David Smith (Sony Classical), Peter McGrath (Audiophon,  
HM) and John Atkinson (Stereophile Magazine).  
A list of their current 618 recordings is available from Meridian Audio on  
request.  
Designers  
The 518 design team included Phil Boddy, Richard Hollinshead, Duncan  
Smith, Bob Stuart and Rhonda Wilson.  
Author: J R Stuart  
518 User Guide  
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Installation  
5
Introduction  
The Meridian 518 Digital Audio Processor is part of the 500 Series of  
advanced high-fidelity equipment.  
In purchasing a Meridian 518 Digital Audio Processor, you have acquired  
a refined piece of equipment that will continue to bring you listening  
pleasure for many years. This manual will enable you to get the most from  
it.  
About this manual  
Because the 518 is such a flexible item, we have divided this manual into  
three parts.  
Part 1 gives an overview of 518 and gives 'how to use' information for the  
two common 'consumer' applications of Control Unit and Resolution  
Enhancement.  
Part 2 is more technical and describes how to use 518 as a Mastering or  
Multimedia Processor.  
Part 3 gives more technical information in Appendices.  
Conventions used in this manual  
506. A number such as 506 refers to a component in the Meridian 500  
Series of audio equipment.  
Display. Whenever a key name is printed in bold typeface, it means that  
you should press this key. If the key name is not in bold type, it  
indicates that the course of action is not required at present, e.g. ‘if  
you want to change the display, press Display' means you can do this,  
but it is not essential as part of the operation currently being  
discussed.  
Standby Italic form normally refers to the state of the 518. In some in-  
stances, a key and the status of the equipment share the same name,  
e.g. the Standby key and the Standby state.  
Radio  
54  
Displays are illustrated in this form.  
1. Sequences of actions are given in numbered lists.  
About the 500 Series  
The Meridian 500 Series is a unique system of digital, analogue and video  
components designed to meet the demand for absolute quality, ease of  
use and lasting value.  
The flexibility of the Meridian 500 Series is such that you can assemble a  
system as simple or as complex as you need, perfectly suited to your  
requirements, and with the ability to add to it or change it at a later date  
should those requirements change.  
The Meridian 500 Series includes a sophisticated communications link, to  
ensure that any configuration of units will work together as a fully  
integrated system. The 500 Series communications system allows you to  
control any combination of units using a single handset, and ensures that  
your commands from the handset are interpreted unambiguously. Any  
unit can be designated as the controller for the system, allowing you to  
position the other units out of range from the handset beam if desired. It  
also allows all the units to be switched off from the front panel of any unit  
in the system.  
518 User Guide  
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Installation  
6
Part 1  
Unpacking the 518  
On opening the carton, you should have found the following parts:  
·
·
·
·
Meridian 518 Digital Audio Processor  
Power cord  
This manual  
500 Series communications lead  
If any of these items is missing, please contact your dealer. We suggest  
that you retain the packing carefully as it provides maximum protection for  
the unit in transit.  
Installing your 518  
General precautions  
Before carrying out any installation, you should ensure that the 518 is  
marked with the correct voltage for your local AC supply. Should this not  
be the case, do not proceed – but contact your dealer.  
As a general rule, you should not make any connections to the 518, or to  
any other component in your system, whilst the AC power supply is con-  
nected and switched on.  
Connections  
There are three types of connection that need to be made to the 518:  
·
·
·
power  
digital audio  
communications.  
Audio connections need to be made to other components in your system.  
Communication connections have to be made to most of the other  
Meridian components in your system in order for them to act as one sys-  
tem. The connections to your 518 are very important and care should be  
taken in deciding which connections to make.  
Connection details are described following page 29.  
Siting  
We recommend the following guidelines for location.  
·
·
The 518 should not be placed on top of a power amplifier.  
Avoid sites where it would be subjected to direct sunlight or where it is  
near a heat source, e.g. a central heating radiator  
Avoid sites where the 518 could be subjected to strong magnetic ra-  
diation, like near a power amplifier.  
·
·
Not too close to a television, or where connecting cables may be sub-  
ject to, or cause, interference.  
Tip In common with all digital products, the 518 emits some radio-fre-  
quency signals. For this reason, try to keep all power cables and network  
leads away from audio, antenna and loudspeaker cables. Some time  
spent laying out the cables carefully will repay you with the best possible  
performance later.  
518 User Guide  
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Overview of 518  
7
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?  
D1  
Input Switch  
D2  
Twin PLL  
42MHz DSP  
Digital Output  
Out  
D3  
Opt  
Control  
Computer  
Front Panel  
RS232  
Internal block diagram for 518  
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.  
518 User Guide  
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Overview of 518  
8
Overview as Preamp (Type 0)  
Conventional analogue systems use a 'preamp' or control unit to gather  
together the various sources and to control the level of signal fed to the  
power amplifier so you can adjust volume.  
Purists know that no matter how well a piece of analogue audio  
electronics is designed, there will always be unwanted and irreversible  
degradation, due to the addition of noise and distortion. Preamps are by  
no means immune from this.  
For this reason, Meridian have for many years been developing an all-  
digital system where digital audio is handled by a digital controller (like  
562) instead of a preamp. In these systems the signal is kept in the digital  
domain right into the DSP loudspeakers. Apart from sophisticated  
loudspeaker technology, the digital signal processing (DSP) in the  
speakers also replaces the volume control.  
Some quality-concious audiophiles (who still don't have DSP speakers)  
prefer to use very simple replacements for the analogue preamp, placing  
a passive volume control between an analogue source such as a CD  
player or DAC and the power amp. This architecture gives very high  
sound quality, but has a number of disadvantages – like it requires a very  
sensitive power amp and has difficulties with impedance matching, hum,  
noise and frequency response in the passive control.  
The Meridian 518 can provide an enormous improvement in the sound  
quality of some systems, by allowing you to dispense with the analogue  
preamp altogether – providing you have a good enough digital–analogue  
converter (DAC) and can route all signals in digital form.  
For these applications – where a DAC can be connected directly to a  
power amp – then 518 provides a radical upgrade by removing the  
troublesome passive control.  
CD Player  
518  
DAC  
Power Amp  
LaserDisc  
DAT  
Using 518 as a 'preamp'  
The system is illustrated above. Up to four digital sources – like CD, DAT  
or LaserDisc (often using the optical input) – are connected to the 518.  
518 is then configured as Type 0 (see page 21) which makes it a system  
controller with a fully-operational volume control.  
The output of 518 is taken to a DAC (or digital power amp); the output of  
the DAC is directly connected to the power amplifier.  
The 518 performs more functions than switching and volume control. In  
summary, it:  
·
·
smooths the sound by de-jittering the incoming data stream,  
performs resolution enhancement by word-length matching, shaped  
dither DAC enhancement and the option of pre-emphasising the DAC.  
For an overview of Resolution Enhancement see page 49.  
Warning! Systems like this can sound incredibly good!  
518 User Guide  
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Overview of 518  
9
What about analogue sources?  
Tuner  
LP  
562  
518  
CD Player  
LaserDisc  
DAT  
Using 518 with a 562  
Analogue sources need to be converted to digital before passing through  
518. Meridian make the 562 and 562V digital controllers, both of which  
have very high quality delta-sigma analogue–digital converters.  
By adding a 562 to the system you will be able to feed 7 analogue  
sources (like radio, tape, even LP) in addition to 5 digital sources. A 562  
also provides full tape copy and 2-room facilities.  
518 and 562 work together seamlessly through the Meridian 500 Comms  
system.2  
What else do I need to know?  
This is a high-performance system, and to be successful, there are a few  
things to consider.  
·
Use a high-quality DAC. Preferably look for at least 18 bit precision.  
The Meridian 563 is an 18 bit converter and is a very good choice. Of  
course, 16 bit DACs will work, and the sound quality improvements  
from 518 will be evident: the drawback is that 16 bit DACs may give  
an audible background hiss when connected directly to a power  
amplifier. The extent of this noise depends on the sensitivity of the  
power amplifier and speaker used – and of course will be no more  
than the noise the DAC currently gives you at high listening levels.  
If the power amp has some adjustment, set its gain to the lowest  
value that also allows 518 to give you the loudest result you need. As  
a guideline, an 18 bit DAC should be quiet enough for a system where  
the DAC maximum output (normally 2V) is well matched to the power  
amp sensitivity.  
·
·
Make sure that the maximum output of the DAC (normally around 2V)  
suits the maximum input level of the power amp. Your dealer will  
advise on this.  
As there is no volume control between the DAC and power amp, it is  
important that either the DAC you use does not have a serious turn-  
on/off thump, or that you always turn the power amp on last and off  
first.  
·
Preferably, the DAC will use analogue de-emphasis.  
2 Setup details: set 518 to Type 0, set 562 to Type 1. Either can be the  
system controller. Autoconfigure (see page 30) makes 562 the controller.  
Make 518 the controller if you want to use the Menu keys on MSR.  
518 User Guide  
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Overview of 518  
10  
Overview as Resolution Enhancement Processor  
(Type 1)  
There are a wide number of applications for this mode of 518: three  
examples are described.  
CD or LaserDisc playback improvement  
Many installations use the 2-box CD player format of CD transport + DAC.  
The CD transport provides a digital output, and of course may be a  
normal CD player where the digital output is used to drive an outboard  
DAC to improve the quality.  
This CD playback system may then have its analogue output connected  
to a preamp or integrated amplifier in the usual way.  
Analogue inputs  
CD Player  
518  
DAC  
Preamp  
LaserDisc  
Using 518 as part of CD playback  
The diagram above illustrates how 518 is added to such a system. The  
picture shows that the source could be a CD transport, a LaserDisc player  
or both.3  
The 518 provides two resolution enhancement methods: de-jittering via  
the twin PLL and DAC optimisation through DSP. These are explained in  
'Overview of Resolution Enhancement' – page 49.  
The de-jittering element is of great importance to some CD players, and of  
enormous significance to any LaserDisc player as they tend to have  
relatively high-jitter output. If you want to use a LaserDisc player for  
serious CD listening, then the de-jittering in 518 is absolutely necessary.  
The DSP DAC optimisation uses the techniques described in Appendix 4.  
One function the 518 provides is matching the wordlength of the source to  
the capability of the DAC, so for example, it can match LaserDisc or CD  
(both 16 bits) to an 18 or 20 bit DAC.  
Normally in this mode, the 518 is not used as a volume control. Optimum  
performance for a disc will come, either from using unity-gain (i.e. 0dB  
gain) or possibly a few dB boost to optimise the disc.  
Meridian DSP speaker improvement  
The Meridian DSP loudspeakers, provide the most advanced performance  
and highest-resolution sound available today. The DSP speakers only  
accept a digital input and in order to use analogue sources a Meridian 562  
or 562V is often added. The 562 provides input handling for up to seven  
analogue signals using its in-built 16 bit delta-sigma analogue-to-digital  
converter (ADC).  
3 Setup details: set 518 to Type 1. Adjust Out to match DAC.  
518 User Guide  
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Overview of 518  
11  
DSP  
Speaker  
Tuner  
LP  
562  
518  
CD Player  
LaserDisc  
DAT  
DSP  
Speaker  
Using 518 with DSP Loudspeakers  
As the diagram shows, a 518 can be placed between the 562 and the  
Meridian DSP speakers. In this case, the 518 is used – very much as it is  
for the earlier CD example – to provide further de-jittering and resolution  
enhancement. The Meridian DSP speakers can read 22 bits on the input  
and have analogue de-emphasis, so 518 can significantly improve the  
sound of this system.4  
Because 518 does not pass on subcode, the time display feature on  
DSP5000 or DSP6000 becomes disabled. However the Meridian Comms  
system keeps the speaker updated on the current track number.  
Meridian Surround improvement  
The Meridian 565 is a world-beating surround decoder. One of its unusual  
features is the ability to accept digital signals directly to the DSP  
decoding. This means, for example, that the signal from a LaserDisc can  
be passed without the distortion of in-built (and often inferior) DACs and  
results in a substantially improved sound.  
The Meridian 565 can drive DSP, active or conventional loudspeakers in  
any combination.  
Tuner  
LP  
562V  
518  
565  
CD Player  
LaserDisc  
DAT  
Using 518 with a 565 Digital Surround Processor  
Whatever the output configuration, the 518 should be placed before the  
565 Digital Surround Processor – so that the precision of the inputs  
(normally 16 bit) can be matched to the 20 bit input capability of 565.5  
4 Setup details: set 518 to Type 1. Set Out to 22 C.  
5 Setup details: set 518 to Type 1. Set Out to 20 C.  
518 User Guide  
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Overview of 518  
12  
Overview as Mastering Processor (Type 2)  
Recorder  
Mixer  
ADC  
DAT  
518  
Recorder  
Using 518 as a Mastering Processor  
The 518 is closely related to the highly respected Meridian 618 Mastering  
Processor; in fact 518 uses identical DSP to the 618 in this mode.  
The Meridian 618 has been used for over three years by some of the  
world's most experienced recording engineers and there is a long and  
growing list of superior CDs that have used 618 in their production. See  
page 4.  
A mastering processor is used during recording, editing and transfer  
processes. In the course of making a CD for example, the music may  
pass through 518 two, three or four times.  
The diagram shows 518 between a recorder – which may be DAT, reel–  
reel, CDR, MO or hard disk – and a source which may be also a recorder  
or an analogue-to-digital converter (ADC).  
The Mastering processor provides these important functions at each  
stage:  
·
·
·
·
·
·
·
·
·
de-jittering  
matching wordlengths output to input  
translating between consumer and professional serial interface modes  
stripping subcode and some flags  
level-shifting to optimise dynamic range  
fading during edits  
multiple re-dithering options  
DSP application of pre-emphasis or de-emphasis  
RS232 control  
Overview as Multimedia Processor (Type 2)  
CDR  
Computer  
ADC  
DAT  
Mixer  
518  
Computer  
Speaker  
CD/DAT  
Using 518 as a Multimedia Processor  
The Multimedia application of 518 is somewhat similar to the Mastering  
Processor just described.  
Inevitably a PC is a very unfriendly place for high-quality sound for a  
number of reasons. The nature of the electrical environment, the block  
(i.e. 'jerky') access of hard-disc data and severe electrical noise combine  
to seriously limit the jitter performance of digital audio functions and the  
analogue performance of sound cards.  
The principle benefits of using 518 in multimedia systems are:  
518 User Guide  
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Overview of 518  
13  
·
·
De-jittering. This is vital to getting good sound when recording or  
playing back from a computer-based sound storage system.  
Matching wordlengths input to output. Hard disc storage systems tend  
to use 16 or 24 bits. While 16 bit storage is quite adequate for simple  
transfer, it does not allow any headroom for manipulation of the  
signals – without degrading noise. 518 can be used to ensure that all  
the headroom in the disc storage is used by boosting the incoming  
signals to full code. 518 is also ideally suited to translating 24 bit  
storage to a downstream 16 bit recording medium like DAT or CDR.  
In fact, the noise-shaping options of 518 allow most of the subjective  
dynamic range of a 20 bit master to be retained in the 16 bit storage  
device.  
·
·
Accurate DSP. The quality of signal processing used in 518 is  
substantially higher than that normally found in PC editors or sound  
API functions. For example, 518 uses the most sophisticated re-  
dithering technology combined with 72 bit internal processing to  
ensure that any level changes or equalisations are made truly  
transparent to the listener. Much of this technology is proprietary to  
Meridian.  
RS232 control. The 518 supports direct RS232 control from a PC–  
effectively turning it into a 2-channel DSP peripheral.  
Customising features  
As the previous sections illustrate, the 518 is very flexible. You have the  
opportunity to significantly customise its functions to give you the  
functionality that exactly suits your application.  
The section ‘Customising 518, an overview' on page 37 describes the  
options in detail.  
We recommend that you first get to know the 518 using one of the  
standard setups, and by working through this manual. Do not be afraid  
later to experiment with customising – we have given you a simple way to  
get back to where you started! (See page 23).  
518 as provided has three standard configurations that we call Type  
settings. Each Type gives a different set of options; this feature is  
described fully on page 23.  
Note By selecting a Type you automatically reset all custom settings for  
518 to that default.  
518 has four operating modes (not to be confused with setup Types):  
·
·
·
·
Normal  
Standby  
Type  
Config  
Normal and Standby are the everyday operating modes: the basic operat-  
ing instructions refer to these.  
Type, and Config are used to make choices about the way 518 works.  
These are described later in the section: ‘Configuring 518, an overview' on  
page 37.  
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Using 518 in Hi Fi Systems  
14  
Starting off with 518  
Checking  
Before turning on the power, check once again that you have made all the  
connections correctly.  
The 518 is designed to be left connected to AC power at all times and can  
be run continuously.  
Switching on  
The power switch is located directly next to the power inlet on the right-  
rear of 518.  
1. Turn on the power switch at the rear of the unit. A small point on the  
display should now be illuminated.  
.
If there is no display  
Check the integrity of the power connections, including any fuses in the  
supply. If the display is still not illuminated, contact your dealer for help.  
Memory  
The 518 stores your latest settings for each Source in non-volatile  
EEPROM memory and automatically returns to these settings either when  
you come back to that Source, or on power-up.  
The settings which are remembered for each Source are:  
·
·
·
·
·
Gain (not volume in Control Unit mode)  
DSP  
Dither  
In  
Out  
Standby  
The entire 500 Series is designed to be left connected to AC power at all  
times.  
This Standby state ensures that the components operate at maximum  
efficiency from the moment you start listening. It is perfectly safe and  
consumes a negligible amount of power. However, when you are not  
going to use your system for an extended period of time, e.g. when you  
are going on holiday, we would advise you to disconnect it from the AC  
power supply.  
Basic operation of 518  
The majority of functions are available from the front panel controls. When  
used as a preamplifier (Type 0), more functions are available using the  
Meridian System Remote control. See ' Advanced operation using the  
Remote Control' on page 15.  
This section describes the front-panel operation for those controls that are  
common to all applications.  
The following sections describe differences when operating 518 as a  
Control unit, as a Resolution Enhancer and as a Mastering processor.  
518 User Guide  
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Using 518 in Hi Fi Systems  
15  
Note 518 can be used with or without other Meridian equipment. When it  
is used as the main system control unit it is normally the ‘System  
Controller’ and operates exactly as described below. Systems including  
other Meridian control units like 562 or 565 or DSP speakers will always  
elect for 518 not to be System Controller and there are some functional  
differences.  
Operating 518 as a Control Unit (Type 0)  
Note Do not use 518 as a Control Unit if the system has a Meridian 565  
or DSP loudspeaker. (Use Type 1)  
Selecting a source  
1. press Source until the input you require is indicated  
2. release Source  
or  
press a Source key on the Remote  
Selecting a source will bring 518 out of Standby.  
Adjusting the volume  
To increase the volume  
1. press , the right-hand volume key on the 518  
or  
press the top red key on the Remote  
To decrease the volume  
1. press , the left hand volume key on the 518  
or  
press the bottom red key on the Remote Control  
As you adjust the volume setting, the display will change to show the cur-  
rent source and volume number. For example:  
would indicate that you were listening to a Compact  
Disc at a volume setting of 65. The volume level dis-  
CD  
65  
played will count up or down and ranges from 1 to 99. Each step is 1dB.  
Subjectively a volume increase of 9dB is equivalent to a doubling of  
loudness. Each volume number represents about a 11% change in loud-  
ness; nine steps to double loudness. In a traditional analogue preamplifier  
using a rotary volume control the mid-way position usually offers  
approximately unity gain – with full volume corresponding to around  
+20dBgain.  
In 518 the unity-gain i.e. 0dB setting is at volume number 87. For normal  
to high-level listening you should expect volume numbers in the region 60  
to 90. For this reason 518 starts at power-up with volume number 87.  
Out  
1. Press Out to cycle between the output word options.  
The Out key is used to set the number of output bits. It is also used to set  
consumer or professional channel-status output format. The choices are:  
16C, 18C, 20C, 22C, 24C, 16P, 18P, 20P, 22P, 24P  
518 User Guide  
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Using 518 in Hi Fi Systems  
16  
The numbers indicate the number of output bits. C and P represent the  
choice of consumer and professional channel status formats respectively.  
Information: 24 audio data bits are always written to the left and right  
output words but the least significant bits, below the number of output bits  
chosen, are set to zero.  
e.g. for 16 C  
16 data bits  
0 0 0 0 0 0 0 0  
e.g. for 18 C  
18 data bits  
0 0 0 0 0 0  
In  
1. Press In to cycle between the input word options.  
The In key sets the number of input bits to be read from each input word.  
The least significant bits below the number of input bits are masked (i.e.  
ignored).  
Note It is extremely important that the number of input bits is equal to or  
greater than the number of data bits available on the input. If input is from  
a device which is known to use some of the 24 data bits for non-audio  
data or status1, the number of input bits must be equal to the number of  
input audio data bits.  
Both professional and consumer channel status input signals are  
acceptable to the 518.  
Dither  
1. Press Dither to cycle between the dither options.  
Appendix 1 shows the frequency shapes of these dithers.  
Flat  
Flat uses additive, white-spectrum, triangular probability-distribution  
(TPDF) dither.  
1. Press Dither again to choose between the dither options.  
HP  
HP (high-pass) uses additive, high-pass, TPDF dither.  
Shape A  
Shape A uses flat dither and a 2nd-order shaper optimised to MAF. 2  
Shape B  
Shape B uses flat dither and a 9th-order shaper optimised to MAP. 3  
Shape C  
1For example, some A/D converters based on Crystal Semiconductor Ô  
converters may have level information embedded below the LSB.  
2MAF, Minimum Audible Field, is the appropriate threshold curve for  
human listeners with normal stereo loudspeakers.  
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Using 518 in Hi Fi Systems  
17  
Shape C uses flat dither and a 9th-order shaper optimised to MAF.  
Shape D  
Shape D uses high-pass dither and a 9th-order shaper optimised to  
MAF.  
Shape E  
Shape E uses high-pass dither and a 2nd-order shaper optimised to  
MAF.  
DSP  
1. Press DSP to select the primary processing mode.  
The display will show:  
Gain  
87  
Gain has a flat frequency response, but the level of the signal level is  
adjusted using a precision dithered multiplication. All the front panel  
keys are available to specify processing.  
1. Press DSP again.  
The display will show:  
Emph  
87  
Emphasis ensures that the output of 518 is always pre-emphasised  
according to the 50/15µs CD standard. 518 uses precision DSP to pre-  
emphasis the signal providing the incoming signal is not already pre-  
emphasised. If the incoming signal is pre-emphasised the red Emph  
light indicates this.  
Emphasis is the recommended mode for most program material  
providing the DAC system is correctly designed and uses analogue de-  
emphasis.  
or:  
De-Emph 87  
De-Emph provides the CD de-emphasis function to very high precision  
when the incoming signal is pre-emphasised. You would use this only  
if you have a DAC which provides digital de-emphasis. This adaptive  
mode ensures that the output of 518 is never pre-emphasised.  
Note Gain functions in Emphasis and De-Emphasis, in fact all the front  
panel keys are available to specify processing.  
Display  
1. Press Display key to select between the following display formats  
Emph  
Pre-emphasis option and gain setting, or  
ShpB 67  
Dither mode and gain setting, or  
CD 67  
67  
Source and gain setting, or  
3MAP, Minimum Audible Pressure, is the appropriate threshold curve for  
human listeners using headphones.  
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Using 518 in Hi Fi Systems  
18  
20C16  
67  
Input/output choice and gain setting, (This example indicates 20 bits of  
input and 16 bits of output in consumer format), or  
44k1  
67  
Sampling frequency and gain. If there is no input signal the display  
would indicate no lock as follows:  
N.L.  
67  
Emphasis Light  
There is a light on the front panel Emph which indicates when the  
channel status suggests that the incoming audio is pre-emphasised. It is  
not affected by the user's settings on the 518 itself.  
Clip Display  
Some of the processing modes in 518 deliberately allow you to increase  
the overall level of the signal. If the output signal exceeds full scale, the  
518:  
·
clips (saturates) at full code (normally sounding benign on short  
overloads), and  
·
displays a clip message like:  
ClipL  
89  
The clip message will indicate whether the overload occurred on Left,  
Right or both.  
Clipping in DSP has nothing like the bad sonic consequences of clipping  
analogue systems. Normally small amounts of clipping cannot be heard.  
Software version  
In Standby:  
1. Press and hold Display.  
The display will show the version number of the microcontroller  
software, followed by the DSP version e.g.:  
DSP  
1.5  
Advanced operation using the Remote Control  
Putting the 518 in Standby  
1. press Standby on the Remote Control  
or  
put another Meridian component into Standby.  
Coming out of Standby  
To start up the 518 from Standby  
1. Select a source from the front panel or the Remote Control (MSR).  
or  
If the 518 is part of a Meridian system, bring any component out of  
Standby. For example start up a Meridian CD-player.  
518 User Guide  
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Using 518 in Hi Fi Systems  
19  
Muting the sound  
The mute facility cuts off the sound by setting the volume level to zero.  
To mute the sound  
1. Press Mute on the Remote Control. The output will mute and the  
display will change to:  
Muted  
To restore the sound  
1. Press Mute a second time.  
The volume level and display will be restored.  
Menu Keys  
When the 518 is used as a control unit and it is the system controller, then  
the four menu keys on the MSR can be used to access the DSP, Dither,  
In and Out menu functions.  
To access a menu  
1. Press w or e on the remote.  
The menu will be displayed.  
To change a menu  
1. Press n or s on the remote.  
Operating 518 as Resolution Enhancer (Type 1)  
Note Do not use Resolution Enhancement mode if you want the 518 to  
provide the volume control. (Use Type 0)  
Volume control  
The 518 does not provide the main system volume control in Resolution  
enhancement (Type 1) mode.  
If 518 is used with other Meridian controllers like 565 or DSP  
loudspeakers, they will provide the volume function and the normal  
Meridian 0–99 volume number display.  
In Resolution Enhancement mode, 518 does provide a secondary gain  
control which allows you to maximise the resolution of down-stream  
processors and DACs by raising each piece to full digital code.  
This function is called 'Gain' and does not follow the system volume  
control.  
Gain control  
Gain control is provided in one decibel steps from +12 dB down to -99 dB.  
1. Press   
The gain will increase in 1dB increments, and the display will show the  
gain in dBs, something like:  
CD  
+2  
1. Press , to decrease the gain.  
2.  
518 User Guide  
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Operation summary  
20  
Memory  
In Resolution Enhancement mode, 518 maintains a continuous memory of  
the DSP, Dither, Gain, In and Out settings for each source.  
So, if you had determined that, e.g. CD should always use Gain 0dB but  
that Radio could always use Emphasis and +2dB, then 518 will remember  
these and automatically reconfigure itself for each source.  
DSP  
In addition to the DSP modes offered in Control Unit (see page 15),  
Resolution Enhancement adds Bypass.  
Bypass transmits all 24 bits on the input to the output without any  
processing.  
Note When Bypass is chosen, all the other front panel keys are disabled.  
Operation summary  
On the 518 front panel  
Key  
Action  
Source  
Display  
Selects Source or input  
Cycle the display through:  
Processing option with gain in dB  
Dither option with gain in dB  
Input/output choices with gain in dB  
Sampling frequency and gain in dB  
Blank  
DSP  
Select main processing method: Bypass,  
Gain, Emphasis, De-emphasis.  
Dither  
In  
Select dither or noise shaper to be used  
Set number of input bits  
Out  
Set number of output bits and consumer or  
professional use of channel status  
Decrease volume/gain  
Increase volume/gain  
s
n
With the Remote Control  
Source keys  
Selects input depending on  
customisation.  
Standby  
Puts the 518 into the Standby  
state.  
Clear  
Autoconfigure (in Standby)  
Access the Menus  
w e  
Change the Menus  
n s  
Fn + Display  
Change 518 Display  
Change the primary volume.  
Red n and s  
Mute  
Mutes output.  
518 User Guide  
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Customising 518: overview  
21  
Customising 518, an overview  
518 is a very sophisticated device with a huge number of options to allow  
you to set up exactly the system you need or to experiment with new  
possibilities.  
Programming 518 is a straightforward process and you should not be  
timid about experimenting. Although the setup is stored in non-volatile  
memory called EEPROM, the EPROM (which you cannot change)  
contains default Type settings and you can return to these at any time.  
Restoring default settings  
1. Switch off any power amplifiers that are connected to 518.  
2. Switch off the 518 using the power switch on the back.  
3. While pressing the Source key on the 518 front panel, switch the  
power on again. The display will read:  
Type  
1
4. Release the Source key  
At this stage you can change the Type from 0 – 2 using the n and s  
Volume keys.  
5. Switch off the 518 using the power switch on the back.  
6. After half a second, switch the 518 power on again.  
Caution Some power amplifiers are very susceptible to small surges that  
may result from the process of switching a preamplifier on and off. Some  
– like the Meridian 205, 555 or 605 incorporate DC-offset protection that  
may be triggered by this process. Meridian active or digital loudspeakers  
are inherently proof against these surges and need not be switched off. In  
general digital products like power amplifiers, recorders etc. will be  
unpredictable when they have the digital signal interrupted.  
518 has two setup options; Type and Config. These together with Normal  
and Standby give the 518 four operating states. The following sections  
give an overview.  
Type: an overview  
Type just described, restores one of the default settings. No further  
actions are possible.  
Config: an overview  
Config mode is used for setting fundamentals of options and control.  
Consequently in Config the outputs of 518 are muted while you make the  
necessary choices. The choices available in Config are outlined in the  
following sections.  
Config: control settings  
In Config you can make selections that effect the way 518 responds to  
certain keys. The main choices of this kind are:  
·
whether the 518 is to auto-configure, or you will determine the  
controller in the system.  
·
·
The ‘address’ of the product.  
whether or not Standby is permitted.1  
1 Standby is not recommended for 'Pro' or Mastering situations  
518 User Guide  
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Customising 518: overview  
22  
·
·
·
whether or not the Bypass DSP option is available.2  
whether or not a blank display option is allowed.  
whether or not the Emphasis DSP option is adaptive – i.e. reacts to  
the incoming emphasis status.  
·
choices on how the volume control operates and displays.  
Details of these are described in the next section.  
Config: sources and inputs  
In Config you can also make selections to do with sources, e.g.  
·
·
·
·
·
·
how many inputs will be active  
which sources you can select  
which key on the remote control selects which source  
the Logo for that input on the 518 display  
the physical input connection to 518.  
the Comms type of the source, i.e. whether it is a Meridian controllable  
source like CD or Radio  
·
the address for that source product  
How to customise 518  
The 518 comes configured in Resolution Enhancement mode (Type 1)  
and needs no customising to become operational.  
There are a very large number of different configurations possible. This  
section tells you how to change the configuration.  
Customising, general procedure  
518 has four operating modes (not to be confused with setup Types):  
·
·
·
·
Normal  
Standby  
Type  
Config  
Normal and Standby are the everyday operating modes: the operating  
instructions refer to these.  
Type and Config are used to make choices about the way 518 works.  
These are described in the section: ‘Configuring 518, an overview' on  
page 37.  
How to change to Type or Config  
To change to Type or Config you use the same basic procedure.  
1. Switch off any power amplifiers that are connected to the system.  
2. Switch off the 518 using the power switch on the back.  
3. While pressing the specific key for the operating mode you want on the  
518 front panel, switch the power on again.  
518 will display a message to inform you which mode it is in.  
4. Release the key  
At this stage you can make the adjustments required.  
In step 3, the front panel key is:  
·
·
·
Type – press and hold Source.  
Config – press and hold Display.  
Normal – do not use any key!  
2 Bypass is not available if the 518 is the system volume control!  
518 User Guide  
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Customise 518 using Type  
23  
Caution Some power amplifiers are very susceptible to small surges that  
may result from the process of switching a preamplifier on and off. Some  
– like the Meridian 205 or 605 incorporate DC-offset protection that may  
be triggered by this process. Meridian active or digital loudspeakers are  
inherently proof against these surges and need not be switched off. In  
general digital products like power amplifiers, recorders etc. will be  
unpredictable when they have the digital signal interrupted.  
How to change back to Normal  
To revert to Normal .  
1. Switch off the 518 using the power switch on the back.  
2. After half a second, switch the 518 power on again.  
Making changes to an existing setup  
Config is a configuration editing mode, it does not reset on entry. Type  
however performs a full reset of all parameters.  
To make any changes to your custom configuration:  
1. Change to Config,  
2. make the changes you want,  
3. change back to Normal.  
Customising using Type  
Type is a mode used specifically to setup 518 into one of three factory-  
preset configurations.  
·
Type resets the following for all three Types.  
Setting  
Controller  
System Address  
Product Address  
Standby  
Type 0  
Type 1  
Type 2  
Auto  
1
Auto  
1
N.Con  
1
1
1
1
Y
Y
N
Y
Bypass  
N
Y
Blank  
Y
Y
N
N
N
dB  
*Emph  
N
N
Volume  
M
##  
N
Volume  
dB  
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Customise 518 using Type  
24  
·
Source-Logo-input mapping as shown below.  
Source  
Logo  
Type 0  
Input  
Type 1  
Input  
Type 2  
Input  
Comms  
type  
CD  
Radio  
LP  
CD  
RD  
LP  
TV  
T1  
T2  
CR  
Cb  
Tx  
D1  
D1  
D1  
D1  
D2  
D3  
D1  
D1  
D1  
D1  
D1  
OP  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
D1  
N
1
2
N
TV  
N
Tape1  
Tape2  
CDR  
Cable  
Text  
D2  
D3  
N
N
N
VCR1  
VCR2  
LD  
V1  
V2  
LD  
N
N
OP  
Selecting Types  
1. Switch off any power amplifiers that are connected to the system.  
2. Switch off the 518 using the power switch on the back.  
3. While pressing the Off key on the 518 front panel, switch the power on  
again. The display will read:  
Type  
1
4. Release the Off key  
5. Use the front-panel and Volume keys to move the selection  
between Types 0 – 2.  
6. When you have the Type you want displayed, wait one second for 518  
to action the choice.  
7. Switch off the 518 using the power switch on the back.  
8. After half a second, switch the 518 power on again to restore Normal  
mode.  
Customising using Config  
In Config you can review and change settings to do with communications,  
control and the hardware options you have. In Config you also make  
choices about the number and types of sources, what the display shows  
when you select them etc. The 518 is initially programmed to Type 1 and  
all Types set up the source configuration as shown in the previous Tables.  
How to use Config  
1. Switch off any power amplifiers that are connected to the system.  
2. Switch off the 518 using the power switch on the back.  
3. While pressing the Display key on the 518 front panel, switch the  
power on again. The display will read:  
Config  
4. Release the Display key, the display will show:  
518 User Guide  
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Customising 518 using Config  
25  
Auto  
Selecting the controller mode  
In Config mode:  
1. Press Display until you see a display like:  
Auto  
2. Use the and , Volume keys to choose between:  
·
·
·
Auto, meaning configuring can be automatic  
Cont, meaning the 518 will be the system controller  
N.Con, meaning the 518 will not be the controller  
Setting the system address for 518  
In Config mode:  
1. Press Display until you see a display like:  
SA=1  
This means the system address is 1. The Meridian 500 Comms system  
allows for up to eight systems operating on the same network. Unless you  
are setting up a Multiroom system, or are advised to do so by Meridian  
support personnel, we suggest you leave this on address 1.  
Setting the product address for 518  
In Config mode:  
1. Press Display until you see a display like:  
PA=1  
This means the product address is 1. The Meridian 500 Comms system  
allows for up to eight products of the same type operating on the network.  
Unless you are setting up a Multiroom system, or are advised to do so by  
Meridian support personnel, we suggest you leave this on address 1.  
Note When customisation is complete, switch the power off and then on  
again to restore Normal mode and to save what you have done.  
Setting the Standby mode for 518  
In Config mode:  
1. Press Display until you see a display like:  
Stby  
Y
This means that Standby mode is available. To prevent Standby chose N.  
2. Use the and , Volume keys to choose between Yes or No.  
Setting the Bypass option for 518  
In Config mode:  
1. Press Display until you see a display like:  
Bypass  
Y
This means that Bypass is available. Bypass prevents the 518 operating  
as a volume control and is therefore it is highly undesirable to access it by  
mistake if you are using 518 to control volume.  
2. Use the and , Volume keys to choose between Yes or No.  
518 User Guide  
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Customising 518 using Config  
26  
Setting the Blank display option for 518  
In Config mode:  
1. Press Display until you see a display like:  
Blank  
Y
This means that a blank display is one of the options offered by the  
Display key. To remove this option chose N.  
2. Use the and , Volume keys to choose between Yes or No.  
Setting the Emphasis option for 518  
In Config mode:  
1. Press Display until you see a display like:  
*Emph  
N
*Emph Y means that pre-emphasis will be 'forced' on the output signal  
irrespective of the incoming channel status (displayed with the Emph  
light). Normally Emphasis is an adaptive setting that guarantees pre-  
emphasis on the output. There may be requirements in mastering where  
pre-emphasis needs to be applied even though incoming emphasis is  
indicated.  
'*Emph N' means use the adaptive method.  
2. Use the and , Volume keys to choose between Yes or No.  
Chose 'Y' to over-ride the incoming emphasis flag1.  
If in doubt chose 'N'. '*Emph Y’ is not needed in normal use.  
Setting the Volume mode for 518  
In Config mode:  
1. Press Display until you see a display like:  
Vol.  
N
In the 500 Comms system there is provision for two volume controls, main  
and secondary.  
2. Use the and , Volume keys to choose between:  
·
N. No means that the gain control in 518 is independent of any  
other Meridian components in the system and is stored by Source.  
M. Volume Main means that the volume control in 518 will follow  
the main Meridian system and respond to the red keys on the  
remote.  
·
·
S. Volume secondary means that the volume control in 518 will  
follow the second volume control in the system and respond to the  
shifted volume command on the remote. (Fn + Volume)  
For further details on shifted commands see the manual supplied with the  
remote control.  
If in doubt choose VolM for a preamp and N for Resolution Enhancement.  
Setting the Volume display  
In Config mode:  
1. Press Display until you see a display like:  
1 Note. *Emph also allows De-emphasis of a signal not shown to be  
emphasised.  
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Customising 518 using Config  
27  
Vol.  
dB  
The gain of 518 can either be displayed in absolute dB in the range -99dB  
to +12dB, or as a Meridian volume number 0 to 99 – where 87  
corresponds to 0dB.  
2. Use the and , Volume keys to choose dB or ##.  
Setting up sources  
For each of the twelve source selection keys on the Remote control you  
choose a display Logo and a physical input connection.  
Normally as shown, we set the CD key to give a CD display with the D1  
(Digital 1) input selected. You may however wish to display CD1 for your  
main CD player and to connect it to D2.  
A full list of possible logos and their meanings is:  
Source  
CD  
Logo  
CD  
RD  
LP  
T1  
Source  
S-VHS  
Betamax  
Camera  
Video 8  
CD-V  
Logo  
SV  
Source  
DAB  
Logo  
DAB  
DSat  
ADC  
Reel  
Radio  
LP  
Dig. Sat  
ADC  
bm  
Ca  
Tape 1  
Tape 2  
CDR  
V8  
R-Reel  
T2  
CD-V  
CD-I  
CD-T  
FM tuner FMTun  
AM tuner AMTun  
MW tuner MWRad  
Cr  
CD-I  
Cable  
Teletext  
VCR 1  
VCR 2  
Cb  
TX  
V1  
V2  
CD-T  
CD Photo CD Photo SW tuner SWRad  
CD Lib CD Li LW tuner LWRad  
CD Jbox CD Jbox Line  
CD-ROM CD-ROM Mic.  
Line  
Mic  
Laserdisc LD  
Satellite  
CDX  
SA  
DAT  
DAT  
Aux  
Aux  
C2  
DCC  
DCC  
Mixer  
Simul.  
Mixer  
Simul  
78 rpm  
VHS  
78 rpm  
VH  
Phono  
Minidisc  
Phono  
Mdisc  
Computer PC  
Choosing source logos  
Note at any time in the source configuring process you can use the front-  
panel Display key or the handset Mute key to return to the root menu  
with a display like ‘Auto'.  
In Config mode:  
1. Press Source until you see a Remote-key (source) + logo display like  
CD  
CD  
2. Press Source until the Remote key name for the source you wish to  
configure is displayed.  
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Customising 518 using Config  
28  
3. Use the and Volume keys until the correct logo is indicated – see  
the list above.  
4. Make changes for all the source options.  
Note If you select the logo ‘N’ the 518 will ignore that key on the Remote  
control and that source will not be offered in the Normal source menu.  
Changing the input for a source  
In Config mode:  
1. Press Source until you see a Remote-key (source) + logo display like  
CD  
CD  
2. Press Source until the Remote key name for the source you wish to  
configure is displayed.  
3. Press DSP.  
you should see the display change to one like:  
CD  
D1  
The Remote control key you are setting up is the source name and it is  
indicated on the left as before. Now the letters on the right indicate which  
of the four physical input connectors will be selected.  
To change the physical inputs:  
1. Use the and Volume keys until the correct one is indicated  
2. Make changes for all the source options by pressing Source.  
Note When customisation is complete, switch the power off and then on  
again to restore Normal mode and to save what you have done.  
Choosing the Comms type for a source product  
This setting currently only applies to a source which is a Meridian CD  
player or Radio tuner.  
In Config mode:  
1. Press Source until you see a Remote-key (source) + logo display like  
CD  
CD  
2. Press Source until the Remote key name for the source you wish to  
configure is displayed.  
3. Press DSP until you see a display like:  
CD  
1C  
4. Use the and Volume keys to chose the Comms type.  
CD players are always 1C, tuners are always 2C. NC means the source is  
not Meridian.  
5. Make changes for all the source options by pressing Source.  
Choosing the address of a source product  
In Config mode:  
1. Press DSP until you see a display like:  
CD  
1A  
2. Use the and Volume keys to choose the product address  
3. Make changes for all the source options by pressing Source.  
518 User Guide  
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Connecting 518  
29  
Connections  
There are three types of connection that need to be made to the 518.  
·
·
·
power, see page 14.  
digital audio, see page 40.  
communications, see page 30.  
Digital audio connections  
Digital connections are made:  
·
from the digital outputs of 518 to your digital power amplifiers, digital  
loudspeakers, digital recording devices, editors.  
to the digital input of 518 from sources like CD, A/D converters,  
mixers, digital recording devices, editors.  
·
Digital connections should be made with either:  
·
·
high-quality 75W screened cable on SPDIF  
high-quality 110W balanced screened cable on AES/EBU.  
For advice on the type of cable we suggest you consult your dealer and  
the manual supplied with the source equipment.  
Meridian has a range of suitable digital interconnects available as  
accessories. We recommend you do not use cables intended for analogue  
connection since these do not usually have the degree of shielding or an  
impedance of 75W. Cable intended for UHF applications like antenna  
down-lead is also unsuitable since it does not shield adequately in the 1–  
30MHz region.  
Warning. We strongly recommend the use of well-screened precision  
coaxial cable. Certain ‘audiophile' cables are not screened. Screened  
cable will minimise RF interaction with your system. Unscreened cables  
for digital connections may cause illegal levels of RF interference.  
Digital input connections  
1. Make digital connections from each of your digital sources to an  
appropriate digital input on 518. The digital inputs on 518 are labelled:  
·
·
D1 to D3 for the three cable inputs, and  
OP for the optical input.  
These inputs are identical in performance and are assigned in Config.  
D1 also has an AES/EBU connection. Only one can be used at a time, i.e.  
D1 is either SPDIF or AES/EBU not both.  
Digital output connection  
1. Make digital connections from the output to the equipment you have  
chosen to follow it.  
You can use both the SPDIF and AES/EBU output connections at the  
same time.  
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Connecting 518  
30  
Communications connections  
Communications connections are only made to other Meridian equipment.  
The following sections describe the major points.  
To connect to other Meridian 500 Series equipment  
1. Connect one of the COMMS sockets on the rear panel of the 518 to  
one of the COMMS sockets on another 500 Series unit, using the 500  
Comms lead supplied.  
2. Connect all the 500 Series products together in this way to form a  
chain (not a loop). The order in which they are connected is not  
important.  
If the system is to operate in 500 mode, then, configure the units with the  
following automatic setup procedure.  
1. Switch all the units to Standby.  
2. Press Clear on the handset.  
Each unit will display:  
Auto  
One unit will then be designated as the controller and display:  
Con  
All the other units will be configured as non-controllers and display:  
NCon  
The system is now set up and ready to use.  
If for any reason the automatic setup does not give the configuration you  
want, you can restore the default operation by selecting a Type or by  
setting the controller status in Config as described on page 21.  
Connecting to Meridian Digital speakers  
1. Connect the phono plug on the end of the M-lead to the digital output  
of the 518.  
4. Connect one of the two DIN plugs on one end of the M-lead to one of  
the COMMS sockets on the back of 518.  
Note There are usually two DIN plugs on an M-lead. Take care to chose  
the correct one and do not force the plug. The second plug is used to  
connect to any 200 Series products in the range.  
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Using 518 for Mastering and Multimedia  
31  
Part 2  
Mastering Processor  
The Meridian 518 Digital Audio Processor has been designed to allow  
the making of better recordings, and in particular to enable the  
production of high-quality, enhanced-definition CDs.  
The predominantly available channels for delivering high-quality sound  
to consumers is stereo, linear-encoded 16 bit PCM. There is also no  
realistic prospect of a widely-available improvement on this capability.  
While CD is limited to 16 bits, we now have A/D converters, recorders  
and editors operating with anywhere between 16 and 24 bit words.  
The Meridian 518 provides the very best quality and combination of  
signal-processing functions for use when preparing material for issue on  
media like CD. In fact, using the unique signal processing in 518, CDs can  
be produced with up to 19-bit subjective dynamic range.  
The functions of 518 have been optimised for use in three stages of  
the production process, namely:  
·
on location, processing the signal between the A/D converter and  
recorder,  
·
·
during transfer of a recording to an editor,  
during transfer from editor to production master.  
In each such step, the word-size can be different, and 518 can make  
these processes optimal.  
The signal-processing used is based on an extensive programme of  
research, and is implemented in DSP with an internal precision of 72  
bits to ensure exceptional transparency. For a very full technical  
background, please see the papers referred to below: copies may be  
obtained from Meridian. 1 2 3 4  
518 also finds applications in professional or consumer replay  
situations. Here the precision gain control and pre/de-emphasis  
processing can replace the system preamp and enhance the dynamic  
range of a D/A converter – see the earlier sections of this manual.  
1J.R. Stuart and R.J. Wilson, "A Search for Efficient Dither for DSP  
Applications", 92nd AES Convention, Vienna 1991, Preprint #3334  
2J.R. Stuart, "Noise: Methods for estimating Detectability and Threshold", 94th  
AES Convention, Berlin 1993, Preprint #3477  
3M.A. Gerzon, P.G. Craven, J.R. Stuart, R.J. Wilson, "Psychoacoustic Noise-  
Shaped Improvements to CD and other Linear Digital Media", 94th AES  
Convention, Berlin 1993, Preprint #3501  
4J.R. Stuart and R.J. Wilson, "Dynamic Range Enhancement Using Noise-  
Shaped Dither Applied to Signals With and Without Pre-emphasis", In  
preparation for AES Convention, Amsterdam 1994.  
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Using 518 for Mastering and Multimedia  
32  
Description  
The Meridian 518 Digital Audio Processor is a general-purpose digital-  
domain DSP engine that operates on or between consumer or  
professional interfaces at sampling frequencies between 32–50kHz and  
with up to 24 bit input and output.  
The supplied user programmes are intended for use in recording, editing,  
mastering and replay situations.  
The primary functions of 518 permit the correct signal processing when  
moving between carriers or channels of different word size. Options are  
also offered – in the form of noise-shaping, gain control and precision pre  
and de-emphasis – to maximise the subjective dynamic range of the final  
carrier or channel. Typical applications would be to use 518 at all stages,  
i.e. between an A/D converter and a recorder; then between the recorder  
and any editor; and finally between the editor and the final carrier.  
518 has been extensively beta-tested, there are many highly-regarded  
commercially-available CDs that have used its processes.  
518 as a Mastering or Multimedia Processor (Type 2)  
This section covers unusual features of 518 operation when used in  
mastering or Multimedia processor mode (Type 2). Please refer to the  
normal operating instructions on page 15 for more details.  
Meridian 500 Comms warning  
We strongly recommend that you do not connect anything to the Comms  
sockets in Type 2. The behaviour of the 518 may be unpredictable.  
If you want to use 518 as a Mastering or Multimedia Processor along with  
other Meridian equipment, we suggest you start from Type 1 and build the  
appropriate functionality in Config.  
Emphasis Light  
There is an Emph light on the front panel which indicates when the  
channel status suggests that the incoming audio is pre-emphasised. It is  
not affected by the user's settings on the 518 itself. Obviously in this  
circumstance, it is not advisable to pre-emphasise again using 518!  
Routinely 518 prevents you from making this mistake, however, against  
the possibility that the incoming channel-status may be wrong, you can  
over-ride this protection, see *Emph on page 26.  
Selecting a source  
1. press Source until the input you require is indicated  
2. release Source  
Gain control  
Gain control is provided in one decibel steps from +12 dB down to -99 dB.  
1. Press ▲  
The gain will increase in 1dB increments, and the display will show the  
gain in dBs, something like:  
D1  
+2  
1. Press , to decrease the gain.  
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Using 518 for Mastering and Multimedia  
33  
Memory  
In Mastering Processor mode, 518 maintains a continuous memory of the  
DSP, Dither, Gain, In and Out settings for each source.  
So, if you had determined that, e.g. D1 is an 18 bit source that should  
always use Gain 0dB but that D2 is 16 bit and can always use Emphasis  
and +2dB, then 518 will remember these and automatically reconfigure  
itself for each source as you switch between them.  
DSP  
1. Press DSP to select the primary processing mode.  
The display will show:  
Bypass  
0
Bypass transmits all 24 bits on the input to the output without any  
processing.  
Note When Bypass is chosen, all the other front panel keys are disabled.  
1. Press DSP again.  
The display will show:  
Gain  
0
Gain has a flat frequency response, but the level of the signal level is  
adjusted using a precision dithered multiplication. All the front panel  
keys are available to specify processing.  
1. Press DSP again.  
The display will show:  
Emph  
0
Emphasis ensures that the output of 518 is always pre-emphasised  
according to the 50/15µs CD standard. 518 uses precision DSP to pre-  
emphasis the signal providing the incoming signal is not already pre-  
emphasised. If the incoming signal is pre-emphasised the red Emph  
light indicates this.  
or:  
De-Emph 0  
De-Emph provides the CD de-emphasis function to very high precision  
– providing the incoming signal is emphasised (Emph light on).  
Note Gain functions in Emphasis and De-Emphasis, and all the front  
panel keys are available to specify processing.  
Display  
1. Press Display key to select between the following display formats  
Emph  
Pre-emphasis option and gain setting, or  
ShpB +2  
Dither mode and gain setting, or  
CD +2  
+2  
Source and gain setting, or  
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34  
20C16  
+2  
Input/output choice and gain setting, (This example indicates 20 bits of  
input and 16 bits of output in consumer format), or  
44k1  
+2  
Sampling frequency and gain. If there is no input signal the display  
would indicate no lock as follows:  
N.L.  
+2  
Clip Display  
Some of the processing modes in 518 deliberately allow you to increase  
the overall level of the signal. If the output signal exceeds full scale, the  
518:  
·
clips (saturates) at full code (normally sounding benign on short  
overloads), and  
·
displays a clip message like:  
ClipL  
+10  
The clip message will indicate whether the overload occurred on Left,  
Right or both.  
Clipping in DSP has nothing like the bad sonic consequences of clipping  
analogue systems. Normally small amounts of clipping cannot be  
detected.  
Making Recordings  
Case 1. The recording is made to the final carrier, DAT or CDR  
at 16 bits  
a) 16-bit A/D – 518 – CDR, use Bypass.  
b) 20-bit A/D – 518 – CDR.  
use Emphasis (if the material has sufficient headroom at high  
frequencies), or:  
use Gain (on the maximum setting which does not cause clipping)  
with:  
·
·
·
Shape B, C or D.  
In set to 20.  
Out set to 16 C (possibly 16 P).  
Case 2. The recording will be further processed: carrier and  
A/D converter have the same word size  
In this case use Bypass.  
Case 3. The recording will be further processed: carrier has  
more bits than the A/D converter  
In this case use Bypass.  
Case 4. The recording will be further processed: the carrier  
has fewer bits than the A/D converter  
Use Emphasis if the material has sufficient headroom at high  
frequencies, or:  
use Gain on the maximum setting which does not cause clipping.  
In both cases, also select:  
·
·
Flat or H.P. dither. You may also use Shape A.  
In set to the number of bits in the A/D converter.  
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35  
·
Out set to the number of bits in the recorder.  
Transfer to editor  
Case 5. The recording and editor are the same word size  
In this case use Bypass.  
Case 6. The recording has fewer bits than the editor  
In this case use Bypass.  
Case 7. The recording has more bits than the editor  
In this case use Emphasis (if the recording is not already pre-  
emphasised) and if there is sufficient headroom at high frequencies, or:  
use Gain on the maximum setting which does not cause clipping.  
In both cases, also select:  
·
·
·
Flat or H.P. dither. You may also use Shape A.  
In set to number of bits on the recording.  
Out set to the number of bits used in the editor.  
Transfer to the final carrier  
Case 8. Editor and final carrier have same word size.  
In this case use Bypass.  
Case 9 Editor has fewer bits than final carrier  
In this case use Bypass.  
Case 10 Editor has more bits than final carrier  
In this case use Emphasis (if the recording is not already pre-  
emphasised) and if there is sufficient headroom at high frequencies, or:  
use Gain on the maximum setting which does not cause clipping.  
In both cases, also select:  
·
·
·
Shape A, B, C or D.  
In set to number of bits on the output of the editor.  
Out set to the number of bits on the final carrier.  
Note In this circumstance, the editor should be set to put out the  
maximum number of bits it can to preserve linearity.  
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About the Noise Shapers  
36  
Noise shaper characteristics  
Each noise shaper presents a different degree of subjective noise  
reduction – we call that its ‘advantage’ – compared with normal dithering  
using white TPDF dither. Each shaper also has a different degree of HF  
boost. The parameters are summarised in the table below.  
Shaper  
Advantage  
44.1kHz  
Pre-emphasis  
48kHz  
Pre-emphasis  
Normal  
0.0dB  
Normal  
0.0dB  
Flat TPDF  
High-pass  
Shape A  
Shape B  
Shape C  
Shape D  
3.4dB  
3.4dB  
3.5dB  
6.4dB  
19dB  
7.0dB  
3.5dB  
6.4dB  
19.6  
7.0dB  
12.2dB  
22.6dB  
17.9dB  
21.5dB  
12.2dB  
23.6dB  
21.4dB  
23.5dB  
15.1dB  
15.3dB  
18.6dB  
19.9dB  
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Additional technical information  
37  
518 Operating Background  
Transparency in digital systems  
Digital audio gives a unique opportunity to deliver exceptional sound  
quality in a recording or broadcast. In the first decade of this technology,  
considerable progress was made developing the gateways – i.e. A/D and  
D/A conversion. The promise of digital audio is only deliverable if the  
digital audio signal is handled with complete integrity.  
It is has been a common misconception among practising engineers that  
the signal is robust once it is in the digital domain. This combined with a  
general misunderstanding about dither, has led to working practises that  
degrade the potential of the recording. Obviously, it is necessary to  
understand the signal processes, and to have a way to process the signal  
optimally.  
The 518 allows you to achieve a transparent channel with the maximum  
subjective dynamic range. This section explains the technical background.  
Digital Audio and Quantisation  
Digital audio is used because it is possible to transmit the data through  
space (broadcast) or time (recording) without any loss of information or  
generation degradation. This property of digital audio makes it extremely  
attractive. The major development in digital audio has been in extending  
our comprehension of the processes of digitisation and reconstruction of  
the original analogue signal.  
Dither  
Dither is an essential lubricant if a digital audio channel that includes  
processing is to remain transparent.  
Transparency in a digital channel is the result of maintaining linearity at both  
high and low levels and not falling prey to signal-processing distortions like,  
for example, noise modulation.  
It is well established that in order for linearity to be maintained, dither  
must be applied at every non-trivial signal processing stage. By non-trivial,  
we include all operations that modify a sample. With very few exceptions,  
arithmetic operations that modify a sample result in an increase in the  
number of bits representing the output result; in a fixed size channel, this  
can therefore lead to truncation or quantisation effects.  
In a recording process, the typical non-trivial operations will be:  
·
·
·
·
·
Truncation and requantisation if the A/D converter has a larger word  
size than the recorder.  
Truncation and requantisation if the recorder has a larger word size  
than the editor.  
Truncation, requantisation and many potential signal-processing  
errors in the editor itself.  
Truncation and requantisation if the editor has a larger word size than  
the final carrier.  
Truncation and requantisation mastering house processes the  
material (e.g. gain shift, dc filtering etc.).  
It is well established that applying dither with triangular probability  
distribution of ± 1 LSB to a quantisation process results in perfect  
linearity, contributes no noise modulation and permits resolution of signal  
elements below the LSB. It is therefore the ideal tool to achieve  
transparent processing.  
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Unfortunately, although this process is generally understood, it is not  
common practise to employ correct dithering procedures at these stages.  
In fact, practising engineers are often under the misapprehension that  
dither is only needed once in a system, or that if there is sufficient noise in  
a recording then further dither will not be needed. This is an important  
misunderstanding that has so often led to lost quality in recordings.  
518 provides two additive triangular probability-distribution dither forms –  
flat and high-pass. The essential difference between them is that H.P.  
dither has a lower subjective noise-floor, being about 3.5dB less audible  
than additive white dither.  
Both spectra are illustrated in Appendix 1.  
Noise Shaping with dither  
Noise-shaping is a technique in which a filtered version of the quantisation  
error plus dither is fed back and subtracted from the quantiser input. By  
this technique, the total noise can be redistributed, moving the noise from  
spectral regions where the listener is sensitive to other regions where they  
are less audible.  
In 518 we provide four different shapers; they are carefully selected for  
their different properties, each optimised for a different application.  
Dynamic Range  
The dynamic range of a digital channel is defined by the maximum level –  
often referred to as full-scale or 0dBFS – and by the quantisation noise  
floor which is itself determined by the sample word-length. A normal  
TPDF dithered quantisation introduces a benign uncorrelated addition to  
the noise-floor.  
A background to this and a method of calculating dynamic range is given  
in the paper [2] referred to on page 31 of this manual.  
From a users point of view, the noise-floor is determined by the number of  
bits; the subjective noise-floor is determined by the spectrum of the noise,  
i.e. the shaper used.  
The most important application where maximising subjective dynamic-  
range occurs is in a word-size reduction. Here the correct strategy for  
maximising dynamic range is to use the Gain feature of 518 to raise the  
overall recording so that it nearly reaches full-scale. (This can be done by  
playing the recording and monitoring with a peak-hold indicator the  
maximum level; then replay increasing the gain sufficient to raise the peak  
to say -1dBFS).  
Further maximising of the subjective dynamic-range can occur by  
minimising the impact of the added noise using a shaper. For example, if  
a 20-bit original recording achieved a peak level of -4dBFS, then  
transferring it to a CD using Gain +3dB and Shape B could result in a 19-  
bit subjective dynamic range on the CD. Transferring it without 518, i.e. by  
truncation, will reduce the recording to 15 bit with unpleasant low-level  
artefacts.  
Pre and De-emphasis  
The use of pre and de-emphasis as signal-processing means of  
optimising the subjective dynamic range of analogue channels, should be  
quite familiar ideas to audio engineers. In particular, pre and de-emphasis  
have been used in channels where the analogue noise level showed an  
increasing level with frequency, e.g. magnetic tape, shellac or vinyl  
grooves and Frequency Modulation. In all these cases, a well-  
documented property of music and speech is exploited, namely that for  
material microphoned at normal listening positions, and of acoustic  
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source, the average and peak spectrum level declines with frequency  
above a few kHz. Best use is therefore made of the channel by pre-  
emphasising high-frequency signals to an extent where they are more  
likely to occupy the capacity of the channel. De-emphasis is applied on  
replay or reception and has the dual benefit of reducing noise and  
distortion from the preceding chain.  
So far, all linear PCM standards used for digital audio permit the use of  
pre and de-emphasis; the universal characteristic being 50/15uS.  
Probably this standard came into play originally because it helped to  
alleviate the very real problems of linearity in early A/D and D/A  
converters.  
More recently, the use of pre-emphasis has been neglected in digital  
audio. The main reasons for this being:  
·
prejudice based on the very considerable difficulty of designing a  
transparent analogue pre-emphasis module in a microphone  
preamplifier.  
·
·
the much-improved quality of A/D and D/A converters.  
the availability of A/D conversion with more significant bits than the  
distribution channel (e.g. CD 16 bits).  
This trend is mistaken, and for suitable material and conditions, a very  
real benefit can be obtained using pre-emphasis. The improvements with  
518 are unique since the noise-shaping is designed for that circumstance  
and the pre-emphasis is effected in the DSP.  
If we used pre-emphasis on the example of the previous section, the  
resulting CD could have a subjective dynamic range of 20 bits.  
Simple rules for using 518  
This section lays out some simple rules for using 518 in three different  
circumstances.  
A step-down in sample word size  
A step-down in sample word size while applying noise-shaping to give the  
channel a subjective dynamic range as close as possible to the input data.  
Such applications include transferring e.g. 20 bit masters to a 16 bit  
carrier like CD. In these cases:  
·
·
·
Use Gain to bring peak level as close to full-scale as possible  
If the programme material permits, use pre-emphasis  
Use Shape B, C or D unless there is to be significant subsequent  
editing – in which case use either Shape A or high-pass dither.  
No change in sample size  
Modification of a signal in a channel where the same number of bits are  
used to define the input and output data. In this case we should be  
concerned with minimising the impact on the subjective dynamic range of  
the output signal. In these cases:  
·
·
·
Use Gain to bring peak level as close to full-scale as possible  
If the programme material permits, use pre-emphasis  
Use Shape A or high-pass dither.  
Step up in dynamic range  
Shifting incoming data to allow the output to have potential for a  
subjective dynamic range that exceeds the input data without increasing  
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the dynamic range of the signal itself. A typical application may be a full-  
range DSP volume control, where e.g. a 16 bit input is modified by a gain  
control function and passed out to a DAC of 18 or 20 bits. In these cases:  
·
·
If the programme material permits, use pre-emphasis  
Use Shape A or high-pass dither.  
Additional technical information  
Specification  
Inputs  
3 cable and one TOSLINK optical.  
Digital serial interface to AES/EBU or SPDIF  
2 channels up to 24 significant bits  
Digital serial interface to AES/EBU or SPDIF  
2 channels up to 24 significant bits.  
32kHz – 48kHz.  
Outputs  
Sampling Frequency  
Twin PLL  
Second phase-lock loop minimises jitter at  
44.1kHz to approx. 3pS rms.  
Input word selection  
16, 18, 20, 22, 24 bits  
Output word selection 16, 18, 20, 22, 24 bits  
Channel status  
Dither options  
Output selectable professional or consumer  
Additive white spectrum TPDF  
Additive high-pass spectrum TPDF  
5 specific types offered, optimised for each  
sampling frequency, with and without pre-  
emphasis and for MAF and MAP hearing  
thresholds.  
Noise shapers  
Processing  
Gain control in 1dB steps from +12 to –99dB  
Digital-domain pre-emphasis  
Digital-domain de-emphasis  
Accuracy  
Display  
72 bit internal precision  
Gain, processing mode, dither, incoming  
emphasis, clipping.  
Digital Subcode  
Channel status only  
Controls  
Dimensions  
Weight  
Source, Display, DSP, Dither, In, Out, Gain  
325 x 100 x 320mm, (12.9 x 3.9 x 12.6")  
5 kg (10 lb.)  
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Help!  
Standby point not lit  
Check the following:  
1. There is AC power connected to the socket on the rear of the 518  
2. The power switch on the rear panel of the 518 is turned on  
If the 518 will still not illuminate, check any fuses in your power supply  
and the fuse in the inlet of the 518. If these are all intact, contact your  
dealer.  
Audible hiss at high volume settings  
The input dynamic range of any recordings you have are at maximum 16  
bit. The reason for this is that CD and other consumer sources use a 16  
bit standard. The analogue sources you have cannot achieve this kind of  
range. For comparison, analogue sources are likely to be of the order of:  
·
·
·
·
FM Radio, 13 bits  
Reel-reel tape, 13 bits  
Cassette tape, 12 bits  
LP, 11 bits.  
Note that there may be a difference between the dynamic-range of the  
source channel when it is operating, and the noise you hear in Standby.  
For example LP normally has lower noise when the stylus is not in the  
groove; similarly tape will be quieter when it is stopped. CD may also be  
quieter when it is stopped, producing so-called ‘digital silence’.  
The 518 has a 16 bit capability from input to output on analogue sources.  
When the volume is turned up high you may hear this dither as a hiss  
when the sources are stopped. This hiss is lower than the background  
noise of your recordings and is of no consequence.  
No output with Meridian 565, DSP speaker or DAC  
Many consumer products will mute when fed a signal in Professional  
format. If you have no sound – try setting Out to C.  
No time display with Meridian DSP speaker  
518 removes unnecessary subcode as a method of reducing jitter and  
therefore improving sound quality.  
Because 518 does not pass on subcode, the time display feature on  
DSP5000 or DSP6000 becomes disabled. However the Meridian Comms  
system keeps the speaker updated on the current track number.  
Communications not working between 518 and other  
Meridian products.  
If you have this problem check the connections carefully.  
Are you using a mix of 200 and 500 mode units?  
Radio interference  
NOTE 518 is a digital audio and computing device which has been de-  
signed to very high standards of electromagnetic compatibility.  
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FCC WARNING: This equipment generates and can radiate radio fre-  
quency energy and if not installed and used correctly in accordance with  
our instructions may cause interference to radio communications or radio  
and television reception. It has been type-tested and complies with the  
limits set out in Subpart J, Part 15 of FCC rules for a Class B computing  
device. These limits are intended to provide reasonable protection against  
such interference in home installations.  
If this equipment does cause or suffer from interference to/from radio or  
television reception then the following measures should be tried:  
1. Reorient the receiving aerial (or antenna) or route the antenna cable of  
the receiver as far as possible from the 518 and its cabling.  
2. Ensure that the receiver uses well-screened antenna cable.  
3. Relocate the receiver with respect to the 518.  
4. Connect the receiver and this product to different AC outlets.  
5. If the problem persists contact your dealer.  
EEC This product has been designed to comply with the limits set out in  
EN55013 and EN55020C.  
REMEMBER to switch all units off before changing any connections.  
Cleaning  
When cleaning the 518 bear in mind that the front of the unit is plastic,  
and the display panel and top surface are glass.  
Disconnect the power cord before cleaning the unit.  
Note Do not use abrasive cleaners on any part of the 518.  
Maintenance & Service  
The Meridian 500 Series of hi-fi components have been carefully de-  
signed to give years of untroubled service, and there are no user-service-  
able parts inside the case, nor do the units require any form of mainte-  
nance.  
In the unlikely event that your 518 fails to function correctly, it should be  
returned, in its original packing, to your Meridian dealer. In case of diffi-  
culty within the UK or USA please contact our sales and service offices  
shown on page 4.  
Outside the UK: contact the importing agent for the territory. A list of  
Meridian agents abroad is available from the above address.  
No responsibility can be accepted for the 518 whilst in transit to the fac-  
tory or an agent and customers are, therefore, advised to insure the unit.  
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Appendix 1 – Noise Shapes  
43  
Part 3  
Appendix 1 – Noise Shapes  
The graphs in this appendix show the relative noise spectra in dB for the  
different shapers, compared with the flat-spectrum dither level for the  
same word-size.  
20dB  
0dB  
-20dB  
0Hz  
5kHz  
10kHz  
15kHz  
20kHz  
25kHz  
Above: noise spectrum using High-Pass additive TPDF dither at 44.1kHz  
10dB  
5dB  
0dB  
-5dB  
-10dB  
-15dB  
0Hz  
5kHz  
10kHz  
15kHz  
20kHz  
25kHz  
Above: noise spectrum for Shape A at 44.1kHz.  
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Appendix 1 – Noise Shapes  
44  
40dB  
30dB  
20dB  
10dB  
0dB  
-10dB  
-20dB  
-30dB  
0Hz  
5kHz  
10kHz  
15kHz  
20kHz  
25kHz  
Frequency  
Above: noise spectrum for Shape B at 44.1kHz  
30dB  
20dB  
10dB  
0dB  
-10dB  
-20dB  
-30dB  
0Hz  
5kHz  
10kHz  
15kHz  
20kHz  
25kHz  
Above: noise spectrum for Shape C at 44.1kHz  
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Appendix 1 – Noise Shapes  
45  
40dB  
30dB  
20dB  
10dB  
0dB  
-10dB  
-20dB  
-30dB  
0Hz  
5kHz  
10kHz  
15kHz  
20kHz  
25kHz  
Above: noise spectrum of shape D at 44.1kHz.  
Above: noise spectrum of shape E at 44.1kHz.  
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Appendix 2 – Hints on Mastering  
46  
Appendix 2 – Hints on Mastering with noise-shaping  
There are a few difficulties associated with employing noise-shaping  
schemes to maximise the subjective dynamic-range of a digital audio  
channel. These are now reviewed.  
Vulnerability of the signal  
The available dynamic range in a channel is only as wide as the  
narrowest step. No matter how much care is taken with a recording, or to  
maintain the maximum word-size right up to a noise-shaped dithered  
truncation to e.g. 16 bits, the whole benefit can be thrown away if at that  
stage a non-dithered signal process is carried out on the material. This is  
not unheard of, a mastering house may e.g. choose to pass the signal  
through an undithered dc filter!  
This caution simply says that every process on the signal leading up to  
delivery to the customer has to be reviewed for its impact on the noise-  
floor and transparency. Such errors will be cumulative, but just one will  
destroy any dynamic-range enhancements.  
Audible results of digital errors and editing  
Normal digital channels have provision for error detection and correction.  
In sophisticated apparatus, short bursts of erroneous samples are  
interpolated to reduce the audible effect. It is becoming more common in  
CD replay systems, that the only error handling is a first-order hold; that is  
when the system detects an erroneous sample, the previous valid sample  
is output in its place.  
This trend has partly been a response to the fact that errors on CD tend to  
be single missing samples at an acceptably low rate. There are however  
marked variations in this performance between players.  
On normal music this strategy results in a minor modification to the  
waveform and it usually passes unnoticed. The introduced sample is of  
similar size to the signal, and is therefore readily incorporated or masked.  
On normal material we also notice that errors occurring in silent passages  
result in near-zero additions which tend to be inaudible.  
Let us now consider the circumstance where a signal has been passed  
through a noise-shaper with a function like Shape D. In loud passages  
errors will be masked just as the normal circumstance. However channel  
errors occurring in quiet or silent passages will tend to result in an audible  
click (since the HF noise is boosted) with little or no material to mask it.  
A similar problem pertains to editing ‘shaped’ material in quiet passages.  
The requirement exists to maintain apparent continuity in the shaped  
noise. We have observed clicks due to replay errors when shaped  
material is re-played on cheap CD players, but no difficulty at all on  
reasonable or up-market units.  
Requirements for D/A conversion  
Noise-shaping can be used to extend the audible dynamic range of a  
channel beyond that which would be expected for a normal digital channel  
of the same word-size. The essential principle by which this is achieved is  
representing numbers below the LSB as an average of successive  
bracketing numbers. For this system to work, the channel must exhibit  
differential linearity equal to the resolution required.  
We can illustrate this best by example. Let us assume that a signal has  
been encoded with 20-bit precision and that a shaper type D has been  
used to convey this signal onto a 16 bit CD channel. Measurement in the  
digital domain shows very clearly the success with which the subjective  
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Appendix 2 – Hints on Mastering  
47  
dynamic range is extended. Implicit in this theory is the fact that the digital  
channel has near-infinite differential linearity, i.e. each bit has a magnitude  
precisely twice or half the magnitude of the next.  
When this signal is applied to a D/A converter some problems may arise.  
First the D/A process may be associated with an oversampling digital  
filter. Commonly these parts take no precautions with regard to dither and  
introduce a quantisation noise-floor themselves at the approximate level  
of the LSB in the filter, thereby obliterating lower-level information in the  
signal. Secondly the D/A converter will not have perfect differential  
linearity – there is no longer any reason why successive bits will maintain  
a precise 2:1 ratio. The effect of this is also equivalent to quantisation at  
the linearity level of the converter.  
In summary therefore, the wide subjective dynamic range inherent in the  
recording cannot be reproduced unless the replay D/A system has both a  
word-size (in terms of associated oversampling filters) and a differential  
linearity equivalent to the original material, which in this example was 20  
bit. The result would be further improved by the correct use of dither and  
noise-shaping in the digital filter.  
That a subjective channel dynamic range of approaching 20 bit can be  
conveyed on a 16 bit channel is quite remarkable. On reflection, it should  
not be surprising that to realise this benefit, both the A/D and D/A sub-  
systems must have the required 20-bit precision.  
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Appendix 3 – RS232  
48  
Appendix 3 – RS232  
The 518 may be operated via its RS232 interface.  
Set the communication settings as follows:  
·
·
·
·
Baud rate 9600  
Data bits 8  
Stop bit 1  
Parity none  
The 518 is operated by sending short command strings on the RS232  
interface. Each command is terminated by a <return> (dec. 13). No echo  
is implemented. Any subsequent <return> on its own repeats the last  
command.  
518 returns useful strings acknowledging the command and giving status  
information.  
Handset Functions  
The following commands emulate the MSR remote control keys.  
Sources send one of: CD, RD, LP, TV, T1, T2, CR, CB, TX, V1, V2, LD  
Numbers send one of: N1, N2, N3, N4, N5, N6, N7, N8, N9, N0, DP  
(decimal point)  
Menus send one of: ML, MR, MP, MM (for w, e , n, s .)  
Source send one of: PR (previous), PL (play), NE (next), PS (pause), FB  
(fast back), ST (stop), FF (fast forward), RC (record), RP (repeat)  
Memory: SR (store), CL (clear)  
Status: DI (display), SB (standby)  
Volume: VP (up), VM (down), MU (mute)  
GoTo Functions  
There are direct access functions that use two-character codes that may  
be followed by additional numbers or parameters.  
VN##  
GN±##  
BP  
Goto volume number  
Goto gain number  
Goto DSP Bypass  
GA  
Goto DSP Gain  
EM  
Goto DSP Emphasis  
DE  
Goto DSP De-emphasis  
Goto dither # (0=flat, 1= HP, ....6=ShapeE)  
Goto input bits ##  
DT#  
IN##  
OU##C  
OU##P  
Goto output bits ## (Consumer format)  
Goto output bits ## (Professional format)  
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Appendix 4 –Resolution Enhancement  
49  
Appendix 4 –Resolution Enhancement  
Resolution enhancement in 518 depends on six techniques.  
1. De-jittering  
2. Dynamic-range optimisation with Gain  
3. Dynamic-range optimisation with Pre-emphasis.  
4. Dynamic-range optimisation with Noise-shaped Dither.  
5. DAC enhancement by using high-frequency dither.  
6. DAC or channel enhancement by word-length matching.  
Jitter and de-jittering  
Digital audio works by representing the acoustic waveform by a series of  
evenly-spaced sample words. In digital-audio systems, it is quite possible  
– in fact usual – for the data to pass without error. Unfortunately, where  
the data is passed from process to process, the exact even timing of the  
samples may become disturbed so that the samples arrive occasionally  
slightly early or late. inaccuracy in the timing of the incoming stream is  
called 'jitter' – and Meridian have been skilled at dealing with this since  
1983.  
When a jittered digital stream is fed to a DAC, the sound is degraded –  
typically a listener will describe it as 'harsh', 'glassy' or 'bright' or lacking in  
'spaciousness'.  
The de-jittering element is of great importance to some CD players, and of  
enormous significance to any LaserDisc player as they tend to have  
relatively high-jitter output. If you want to use a LaserDisc player for  
serious CD listening, then the de-jittering in 518 is absolutely necessary.  
Another interesting aspect of jitter is that the current AES/EBU and SPDIF  
interfaces use coding that causes some signal-dependent jitter to be  
introduced. So, we can de-jitter a stream, but if it is then passed through a  
series of digital interfaces then it will almost certainly benefit from de-  
jittering again. Now, jitter does no harm in the digital domain: it is only  
important that the stream be correct going into the final converter – which  
in a Meridian system may be a DAC like 563, a Surround Processor like  
565 or a DSP loudspeaker.  
Figure 1. Showing jitter spectrum of twin PLL.  
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Appendix 4 –Resolution Enhancement  
50  
The block diagram on page 7 shows the twin phase-lock-loop which 518  
uses to smooth out the digital sample stream. Each loop acts as a  
progressive 'flywheel' – following the average sample rate exactly – but  
removing short-term speed unevenness.  
Dynamic-range  
The dynamic range of a channel or system is determined by the ratio  
between the loudest signal it will carry without distortion and the  
background noise.  
For digital signals the loudest signal – full output of the channel – is called  
full-scale and this level uses all the available bits.  
In a system using digital components, the background noise may be  
determined by:  
·
·
·
the analogue input signal  
the analogue output components like DAC, preamp or power amp  
the smallest word-size in the digital chain.  
For digital systems to be transparent, dither is needed – this is described  
on page 37. Whether the dither is added at the analogue–digital  
conversion stage or later, it produces a defined noise-floor.  
100  
80  
60  
40  
20  
16  
0
18  
-20  
20  
10Hz  
100Hz  
10kHz  
Frequency1kHz  
Figure 2. Showing audibility of noise in dithered channels of  
different wordsize at very high listening levels.  
In the diagram above, an audio system has been modelled for the loudest  
reasonable listening circumstance – where peak levels reach 120dB spl.  
The 'U'-shaped curve is the threshold of human hearing – sounds below  
this are inaudible. The three curves show the human-audible-significance  
of the dither level in 16, 18 and 20 bit channels. The diagram shows that  
for a digital audio system to reproduce the whole scope of human hearing  
without noise – 19 bits are needed.  
For interest and comparison, the diagram below compares this  
circumstance with LP records where the playback is set for 115dB  
maximum.  
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Appendix 4 –Resolution Enhancement  
51  
Figure 3. Showing the audibility of noise in the LP system for  
comparison with digital channels.  
Dynamic-range optimisation with Gain  
The noise-floor of a digital system is determined absolutely by the lowest  
preceding wordsize. For nearly all commercial material this is 16 bits.  
518 allows you to get the best out of whatever comes next, by making  
sure that the full output capability is used. Gain can be used in Resolution  
Enhancement and Mastering to boost the level of the signal to fill the  
available capacity.  
For some reason, many CDs are recorded well below maximum level. By  
boosting these we are able to reduce the audible effect of noise in  
subsequent processing, or digital filters in DACs, or in the analogue  
electronics.  
Getting this right is easy – 518 immediately tells you if had to 'clip' the  
output because you asked for too much. See page 18.  
Dynamic-range optimisation with Pre-emphasis  
Real-world music and speech signals do not have equal energy at all  
frequencies. Typically the loudest sounds happen in the mid-range and  
peak levels are much reduced above 5kHz.  
This fact has been exploited extensively in audio systems over the years,  
with a system known as pre-emphasis.  
Input  
Pre-emphasis  
Channel  
De-emphasis  
Using Pre-emphasis and de-emphasis to improve channel performance  
The diagram above shows the general pre-emphasis method. To take  
best advantage of the channel – which could be an AM or FM radio link,  
an LP record, a tape recording, a CD or a DAC – high-frequency signals  
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Appendix 4 –Resolution Enhancement  
52  
are boosted. This boost process is called pre-emphasis. Now, in the  
channel, the energy is more evenly distributed with frequency, and any  
high-frequency noise and distortion in the channel is further below the  
signal. In other words we get a better distortion and noise result in the  
channel.  
Before playing back the signal, we need to de-emphasise it to bring the  
overall frequency response back to where it should have been. By cutting  
the high-frequencies back, we also reduce the noise and distortion  
introduced in the channel.  
This process is used everyday for FM broadcast, tape and cassette  
recording, for LP (RIAA pre- and de-emphasis) and for some CDs.  
Now, boosting high frequencies is possible only when the program does  
not have too much high-frequency content. Obviously anything that has  
been through a pre- and de-emphasis process has the required spectrum.  
The diagram below shows the pre-emphasis and de-emphasis curves for  
CD – which are the curves used by 518. You can see that the highest  
frequencies are boosted by nearly 10dB in the channel (on the disc).  
Figure 4. Showing CD pre- and de-emphasis curves.  
The 518 obtains resolution enhancement in making CD recordings by  
using this pre-emphasis. All CD players know how to de-emphasise this  
signal and recognise the pre-emphasis flag. When a signal coming in to  
518 is pre-emphasised, the Emph light comes on. When 518 adds pre-  
emphasis to a signal, the digital audio output stream carries an industry-  
standard indication of pre-emphasis to tell downstream devices how to  
handle this signal.  
The 518 obtains resolution enhancement in playback systems by boosting  
the high-frequency signals as it travels through signal processing or the  
digital filters and conversion parts of a DAC. In the above diagram  
'Channel' can be the digital and conversion part of an outboard converter.  
The last block, 'De-emphasis' is normally in the final analogue sections of  
the converter.  
Well-designed converters use analogue de-emphasis so that all the noise  
of the digital filters and converter are reduced. There are some cheap  
implementations around that use digital-de-emphasis. This is bad design  
and the benefits of this type of resolution enhancement are reduced if  
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Appendix 4 –Resolution Enhancement  
53  
such converters are used. Meridian has always used correct analogue de-  
emphasis in its designs.  
By wrapping 72-bit precision pre-emphasis and analogue de-emphasis  
around a DAC, it effectively gains:  
·
·
·
one bit noise reduction  
two-bit increase in high-frequency resolution  
more than ten-fold (20dB) reduction of converter noise.  
These are substantial gains and are clearly audible on a good system.  
On some material, using pre-emphasis will raise the overall signal level to  
give 'clip' messages. It is still a great step forward to use pre-emphasis  
with some overall gain reduction. In other words, if using pre-emphasis on  
a piece of music causes clipping, try using Emphasis with the gain  
reduced to –2 or –3dB. You are still winning on resolution with most DACs  
up to –6dB.  
100  
80  
60  
40  
HP  
20  
16  
0
18  
HP_Deem  
-20  
10Hz  
100Hz  
1kHz  
10kHz  
Figure 5. Showing the effect on audibility of the 518's High-  
pass and Flat dithers. Also showing the noise reduction from  
de-emphasis.  
Dynamic-range optimisation with Noise-shaped  
Dither  
The section following page 37 describes some of the background to  
noise-shaping.  
Essentially noise-shaping works by an averaging method that is well  
matched to human hearing. The noise-floor of the system is shaped by  
moving energy from the mid-range – where listeners are most sensitive –  
to high frequencies. A correctly designed noise-shaper allows the noise of  
the channel to be made inaudible and allows resolution well below the  
normal wordsize.  
The diagram below shows how 518 can obtain inaudible noise and  
effectively 20 bit resolution on a 16 bit CD!  
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Appendix 4 –Resolution Enhancement  
54  
100  
80  
60  
40  
20  
0
SBM  
Shape C  
Shape D  
-20  
10Hz  
100Hz  
1kHz  
10kHz  
Figure 6. Showing the effect on audibility of the 518's Shapes  
C and D (C using pre-emphasis).  
DAC enhancement by using high-frequency dither  
The graphs above and in Appendix 1 (page 43) show that some of the  
noise-shapers produce quite a lot of supersonic noise. This high level of  
dither can have a very positive effect on DACs by causing them to  
represent each level by averaging a large a number of different levels.  
This high-frequency 'lubricant' tends to smooth out truncation and linearity  
problems in real-world DACs.  
Try the various shapes and see which one you like best in your system.  
DAC or channel enhancement by word-length  
matching  
Digital systems work best if the input data is matched to the correct  
wordsize for the device. Particularly where the signal has a larger  
wordsize than the following device, then truncation distortion will arise.  
The effects are real, but more subtle the other way round and are to do  
with jitter and linearity.  
In general 518 should be set to match the input and output wordlengths to  
the incoming signal and following equipment. That will produce the  
cleanest sound.  
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Index  
55  
Index  
EPROM,version number, 18  
Gain control, 19  
500-Series, 5  
562, 9  
565  
using with, 11  
Help!, 41  
Hiss, 41  
Acknowledgements, 4  
AES/EBU  
digital audio connections, 29  
Analogue sources, 9  
Autoconfigure, 30  
Input  
changing for a source, 28  
choosing in Config, 28  
digital connections, 29  
Inside 518, 7  
Installation  
Background noise, 41  
Bypass, 33  
customising, 13  
general, 6  
siting, 6  
Types, 13  
Introduction, 5  
Cable  
for digital audio, 29  
CD improvement, 10  
Clip  
display, 18, 34  
Communication  
making connections, 30  
Config  
Jitter, 49  
LaserDisc improvement, 10  
Logo, 27  
how to get into, 22  
how to use, 24  
overview, 21  
Mastering, 31  
examples, 34  
hints, 46  
how to use, 32  
Memory, 14, 20  
Menus, 19  
Multimedia, 12  
how to use, 32  
Mute  
Connections  
AES/EBU, 29  
Communications, 29, 30  
digital, 29  
digital audio, 29  
general, 6  
power, 29  
Contents, 2  
Customising  
demuting, 19  
how to, 19  
how to, 22  
making changes, 23  
overview, 21  
using Config, 24  
using Type, 23  
with Config, 21  
with Type, 21  
Noise shape plots, 43  
Noise shapers, 36  
Noise, audible background, 41  
Normal  
how to get back to, 23  
Default settings, 21  
Demute. see Mute  
Digital  
connection, 29  
Display, 17  
Operating  
as preamp, 15  
summary, 20  
Output  
digital audio connections, 29  
Overview as preamp, 8  
Overview as resolution enhancer, 10  
Overview of mastering, 12  
Overview of multimedia processor, 12  
logos, 27  
Dither explained, 37  
DSP, 17, 33  
DSP speaker improvement, 10  
Dynamic range, 41, 50  
Dynamic range explained, 38  
Planning a setup, 7  
Power switch, 14  
Preamp  
Emph light, 18  
Emphasis explained, 38  
Emphasis light, 18  
overview, 8  
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Index  
56  
Pre-emphasis explained, 38  
Programming. see Customising  
Surround sound, 11  
Switching on, 14  
Radio interference, 41  
Recording, 34  
Remote control, 18  
Transfers, 35  
Transparency explained, 37  
Type  
Repacking 518. see Unpacking  
Resolution enhancement explained, 49  
Resolution enhancer, 19  
Restoring defaults, 21  
RS232, 48  
how to get into, 22  
overview, 21  
Unpacking 518, 6  
Using  
as control unit, 15  
as mastering processor, 32  
as resolution enhancer, 19  
Service  
where to get, 42  
Setup. see Customising  
automatic, 30  
how to get into, 22  
Specifications, 40  
Standby  
Version. see EPROM  
Volume  
display, 15  
numbers, 15  
Volume, adjusting, 15  
display, 14  
getting into, 18  
to get out of, 18  
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Notes  
57  
Notes  
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Notes  
58  
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