MERIDIAN 518 USER MANUAL © 1992, 1993, 1995
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 ...............
Simple rules for using 518 ..................40 Additional technical information .........42 Appendix 2 – Hints on Mastering with noise-shaping ......................... 47 Specification .........................................42 Appendix 3 – RS232............................. 49 Help! ......................................................43 Standby point not lit ...........................43 Audible hiss at high volume settings.........................................
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.
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.
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.
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.
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.
Overview of 518 9 What about analogue sources? Tuner LP CD Player 562 518 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.
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.
Overview of 518 11 DSP Speaker Tuner LP CD Player 562 518 LaserDisc DSP Speaker DAT 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.
Overview of 518 12 Overview as Mastering Processor (Type 2) Recorder Mixer ADC 518 Recorder DAT 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.
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.
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 rightrear of 518. 1. Turn on the power switch at the rear of the unit. A small point on the display should now be illuminated. .
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.
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 0 0 In 1. Press In to cycle between the input word options.
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.
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.
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.
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.
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.
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.
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.
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 CD D1 D1 D1 1 Radio RD D1 D1 N 2 LP LP D1 D1 N – TV TV D1 D1 N – Tape1 T1 D2 D1 D2 – Tape2 T2 D3 D1 D3 – CDR CR D1 D1 N – Cable Cb D1 D1 N – Text Tx D1 D1 N – VCR1 V1 D1 D1 N – VCR2 V2 D1 D1 N – LD LD OP D1 OP – Selecting Types 1.
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.
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.
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.
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.
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.
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).
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.
Using 518 for Mastering and Multimedia 32 Description The Meridian 518 Digital Audio Processor is a general-purpose digitaldomain 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.
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.
Using 518 for Mastering and Multimedia 20C16 34 +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.
Using 518 for Mastering and Multimedia • 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.
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 Normal Pre-emphasis 48kHz Normal Pre-emphasis Flat TPDF 0.0dB 3.4dB 0.0dB 3.4dB High-pass 3.5dB 7.0dB 3.5dB 7.0dB Shape A 6.4dB 12.2dB 6.
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.
Additional technical information 38 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.
Additional technical information 39 source, the average and peak spectrum level declines with frequency above a few kHz. Best use is therefore made of the channel by preemphasising 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.
Additional technical information 40 the dynamic range of the signal itself. A typical application may be a fullrange 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 Digital Subcode 3 cable and one TOSLINK optical.
Support information 41 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.
Support information 42 FCC WARNING: This equipment generates and can radiate radio frequency 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.
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. Noise spectrum 20dB 0dB -20dB 0Hz 5kHz 10kHz 15kHz 20kHz 25kHz Frequency Above: noise spectrum using High-Pass additive TPDF dither at 44.
Appendix 1 – Noise Shapes 44 40dB Noise Spectrum 30dB 20dB 10dB 0dB -10dB -20dB -30dB 0Hz 5kHz 10kHz 15kHz 20kHz 25kHz 20kHz 25kHz Frequency Above: noise spectrum for Shape B at 44.1kHz 30dB Noise Spectrum 20dB 10dB 0dB -10dB -20dB -30dB 0Hz 5kHz 10kHz 15kHz Frequency Above: noise spectrum for Shape C at 44.
Appendix 1 – Noise Shapes 45 40dB Noise Spectrum 30dB 20dB 10dB 0dB -10dB -20dB -30dB 0Hz 5kHz 10kHz 15kHz 20kHz 25kHz Frequency Above: noise spectrum of shape D at 44.1kHz. Above: noise spectrum of shape E at 44.1kHz.
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.
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.
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 (dec. 13). No echo is implemented. Any subsequent on its own repeats the last command. 518 returns useful strings acknowledging the command and giving status information.
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.
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.
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.
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.
Appendix 4 –Resolution Enhancement 53 such converters are used. Meridian has always used correct analogue deemphasis 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.
Appendix 4 –Resolution Enhancement 54 100 80 dB spl 60 40 20 SBM Shape C 0 -20 10Hz Shape D 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.
Index 55 Index EPROM,version number, 18 500-Series, 5 562, 9 565 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 overview, 21 Connections AES/EBU, 29 Communications, 29, 30 digital, 29 digital audio, 29 general, 6 power, 29 Contents, 2 Customising how to, 22 making ch
Index Pre-emphasis explained, 38 Programming. see Customising Surround sound, 11 Switching on, 14 Radio interference, 41 Recording, 34 Remote control, 18 Repacking 518. see Unpacking Resolution enhancement explained, 49 Resolution enhancer, 19 Restoring defaults, 21 RS232, 48 Transfers, 35 Transparency explained, 37 Type how to get into, 22 overview, 21 Service where to get, 42 Setup.
Notes 57 Notes 518 User Guide
Notes 58 518 User Guide
