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Meridian Digital Audio Processor 518 User Manual

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MERIDIAN 518 USER MANUAL
©
1992, 1993, 1995

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Summary of Contents for Meridian Digital Audio Processor Meridian 518

  • Page 1 MERIDIAN 518 USER MANUAL © 1992, 1993, 1995...

  • Page 2: Table Of Contents

    Contents Sales and service in the UK ...4 Sales and service in the USA...4 Designed & manufactured in the UK by...4 Acknowledgements ...4 Introduction ...5 About this manual ...5 Conventions used in this manual ...5 About the 500-Series ...5 Part 1 ...6 Unpacking the 518...6 Installing your 518 ...6 General precautions ...6...
  • Page 3 Simple rules for using 518 ...40 Additional technical information ...42 Specification ...42 Help! ...43 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 between 518 and other Meridian products.

  • Page 4: Sales And Service In The Uk

    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 &...

  • Page 5: Introduction

    Installation 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.

  • Page 6: Part 1

    Installation 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.

  • Page 7: Planning Setup Of 518

    Overview of 518 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.

  • Page 8: Overview As Preamp (Type 0)

    Overview of 518 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.
  • Page 9 Overview of 518 What about analogue sources? CD Player LaserDisc 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.

  • Page 10: Overview As Resolution Enhancement Processor (Type 1)

    Overview of 518 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.
  • Page 11 Overview of 518 Tuner CD Player LaserDisc 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.

  • Page 12: Overview As Mastering

    Overview of 518 Overview as Mastering Processor (Type 2) 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.

  • Page 13: Customising Features

    Overview of 518 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 –...

  • Page 14: Starting Off With 518

    Using 518 in Hi Fi Systems 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.

  • Page 15: Operating 518 As A Control Unit (Type 0)

    Using 518 in Hi Fi Systems 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.

  • Page 16: Dither

    Using 518 in Hi Fi Systems 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.

  • Page 17: Dsp

    Using 518 in Hi Fi Systems 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.

  • Page 18: Emphasis Light

    Using 518 in Hi Fi Systems 20C16 Input/output choice and gain setting, (This example indicates 20 bits of input and 16 bits of output in consumer format), or 44k1 Sampling frequency and gain. If there is no input signal the display would indicate no lock as follows: N.L.

  • Page 19: Muting The Sound

    Using 518 in Hi Fi Systems 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...

  • Page 20: Memory

    Operation summary 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.

  • Page 21: Customising 518, An Overview

    Customising 518: overview 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.

  • Page 22: How To Customise 518

    Customising 518: overview whether or not the Bypass DSP option is available. 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.

  • Page 23: Customising Using Type

    Customise 518 using Type 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.

  • Page 24: Customising Using Config

    Customise 518 using Type Source-Logo-input mapping as shown below. Source Radio Tape1 Tape2 Cable Text VCR1 VCR2 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.
  • Page 25 Customising 518 using Config Auto Selecting the controller mode In Config mode: 1. Press Display until you see a display like: Auto 2. Use the 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:...
  • Page 26 Customising 518 using Config Setting the Blank display option for 518 In Config mode: 1. Press Display until you see a display like: Blank This means that a blank display is one of the options offered by the Display key. To remove this option chose N. 2.

  • Page 27: Setting Up Sources

    Customising 518 using Config Vol. 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 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.
  • Page 28 Customising 518 using Config 3. Use the 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.

  • Page 29: Connections

    Connecting 518 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.

  • Page 30: Communications Connections

    Connecting 518 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.

  • Page 31: Part 2

    Using 518 for Mastering and Multimedia 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.

  • Page 32: Description

    Using 518 for Mastering and Multimedia 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.

  • Page 33: Memory

    Using 518 for Mastering and Multimedia 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.

  • Page 34: Clip Display

    Using 518 for Mastering and Multimedia 20C16 Input/output choice and gain setting, (This example indicates 20 bits of input and 16 bits of output in consumer format), or 44k1 Sampling frequency and gain. If there is no input signal the display would indicate no lock as follows: N.L.

  • Page 35: Transfer To Editor

    Using 518 for Mastering and Multimedia 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.

  • Page 36: Noise Shaper Characteristics

    About the Noise Shapers 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.

  • Page 37: Operating Background

    Additional technical information 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.
  • Page 38 Additional technical information 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.

  • Page 39: Simple Rules For Using 518

    Additional technical information 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.

  • Page 40: Additional Technical Information

    Additional technical information 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.

  • Page 41: Help

    Support information 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.

  • Page 42: Cleaning

    Support information 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.

  • Page 43: Part 3

    Appendix 1 – Noise Shapes 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 -20dB Above: noise spectrum using High-Pass additive TPDF dither at 44.1kHz 10dB -5dB...
  • Page 44 Appendix 1 – Noise Shapes 40dB 30dB 20dB 10dB -10dB -20dB -30dB Above: noise spectrum for Shape B at 44.1kHz 30dB 20dB 10dB -10dB -20dB -30dB Above: noise spectrum for Shape C at 44.1kHz 5kHz 10kHz 15kHz Frequency 5kHz 10kHz 15kHz Frequency 20kHz...
  • Page 45 Appendix 1 – Noise Shapes 40dB 30dB 20dB 10dB -10dB -20dB -30dB Above: noise spectrum of shape D at 44.1kHz. Above: noise spectrum of shape E at 44.1kHz. 5kHz 10kHz 15kHz Frequency 20kHz 25kHz 518 User Guide...

  • Page 46: Appendix 2 - Hints On Mastering With Noise-Shaping

    Appendix 2 – Hints on Mastering 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.
  • Page 47 Appendix 2 – Hints on Mastering 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.

  • Page 48: Appendix 3 - Rs232

    Appendix 3 – RS232 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.

  • Page 49: Appendix 4 -Resolution Enhancement

    Appendix 4 –Resolution Enhancement 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.

  • Page 50: Dynamic-Range

    Appendix 4 –Resolution Enhancement 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.

  • Page 51: Dynamic-Range Optimisation With Gain

    Appendix 4 –Resolution Enhancement 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.
  • Page 52 Appendix 4 –Resolution Enhancement 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.

  • Page 53: Dynamic-Range Optimisation With Noise-Shaped Dither

    Appendix 4 –Resolution Enhancement 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.

  • Page 54: Dac Enhancement By Using High-Frequency Dither

    Appendix 4 –Resolution Enhancement 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.

  • Page 55: Index

    Index Index 500-Series, 5 562, 9 using with, 11 Acknowledgements, 4 AES/EBU digital audio connections, 29 Analogue sources, 9 Autoconfigure, 30 Background noise, 41 Bypass, 33 Cable for digital audio, 29 CD improvement, 10 Clip display, 18, 34 Communication making connections, 30 Config how to get into, 22 how to use, 24...
  • Page 56 Pre-emphasis explained, 38 Programming. see Customising Radio interference, 41 Recording, 34 Remote control, 18 Repacking 518. see Unpacking Resolution enhancement explained, 49 Resolution enhancer, 19 Restoring defaults, 21 RS232, 48 Service where to get, 42 Setup. see Customising automatic, 30 how to get into, 22 Specifications, 40 Standby...

  • Page 57: Notes

    Notes Notes 518 User Guide...
  • Page 58 Notes 518 User Guide...

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