Meridian America Meridian 518 manual Showing CD pre- and de-emphasis curves

Page 52

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

518 User Guide

Image 52
Contents 1992, 1993 Contents Appendix 4 -Resolution Enhancement Simple rules for usingAppendix 2 Hints on Mastering Sales and service in the UK Sales and service in the USADesigned & manufactured in the UK by AcknowledgementsIntroduction About this manualAbout the 500 Series Conventions used in this manualInstalling your General precautionsUnpacking ConnectionsPlanning setup Whats inside a 518?Overview as Preamp Type What about analogue sources? What else do I need to know?CD or LaserDisc playback improvement Overview as Resolution Enhancement Processor TypeMeridian DSP speaker improvement Meridian Surround improvement Overview as Mastering Processor Type Overview as Multimedia Processor TypeCustomising features ∙ Normal ∙ Standby ∙ Type ∙ ConfigSwitching on Starting off withBasic operation StandbyAdjusting the volume Operating 518 as a Control Unit TypeSelecting a source OutDither FlatShape a Shape BDisplay Advanced operation using the Remote Control Operating 518 as Resolution Enhancer Type Volume controlMuting the sound Menu KeysOperation summary With the Remote ControlMemory Restoring default settings Config an overviewConfig control settings Customising 518, an overviewHow to customise Customising, general procedureConfig sources and inputs How to change to Type or ConfigCustomising using Type How to change back to NormalMaking changes to an existing setup Setting Type ControllerCustomising using Config How to use ConfigConfig Selecting TypesSelecting the controller mode Setting the system address forSetting the product address for Setting the Standby mode forSetting the Blank display option for Setting the Emphasis option forSetting the Volume mode for Setting the Volume displayChoosing source logos Setting up sourcesVol. dB Choosing the Comms type for a source product Changing the input for a sourceChoosing the address of a source product Connections Digital audio connectionsDigital input connections Digital output connectionConnecting to Meridian Digital speakers Communications connectionsTo connect to other Meridian 500 Series equipment ConPart Mastering ProcessorDescription As a Mastering or Multimedia Processor TypeMeridian 500 Comms warning D1 +2Emph +2 ShpB +2Making Recordings Transfer to editor Transfer to the final carrierNoise shaper characteristics Shaper Advantage 44.1kHz 48kHz Normal Pre-emphasisOperating Background Transparency in digital systemsDigital Audio and Quantisation DitherDynamic Range Noise Shaping with ditherPre and De-emphasis Simple rules for using Step-down in sample word sizeNo change in sample size Step up in dynamic rangeSpecification Additional technical informationHelp Cleaning Maintenance & ServicePart Appendix 1 Noise Shapes NoiseAbove noise spectrum for Shape B at 44.1kHz 0Hz 5kHz 10kHz 15kHz 20kHz Vulnerability of the signal Audible results of digital errors and editingAppendix 2 Hints on Mastering with noise-shaping Requirements for D/A conversionAppendix 2 Hints on Mastering Handset Functions Appendix 3 RS232GoTo Functions Appendix 4 -Resolution Enhancement Jitter and de-jitteringDynamic-range FrequencyDynamic-range optimisation with Gain Dynamic-range optimisation with Pre-emphasisShowing CD pre- and de-emphasis curves Dynamic-range optimisation with Noise-shaped Dither DAC enhancement by using high-frequency dither DAC or channel enhancement by word-length matchingContents IndexIndex User Guide User Guide