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CEDAR Duo – declickle and auto dehiss

Decrease the amount of attenuation from -40.0 to 0.0, at which point you will hear that the

processed signal is identical to the unprocessed signal. This is because the Attenuation control is

limiting the amount of noise removal to 0dB - i.e. there is no effect.

Now increase the amount of Attenuation as defined by the material and your taste. You may

find that, if the Bias is too high, you can only increase the Attenuation by a few dBs before the

signal starts to sound muffled. If the Bias is too low, you can have more Attenuation, but with

reduced effect.

Iterating the Procedure

You may now wish to attempt to find a better value for the Bias. Having done this you will

probably wish to modify the LF Bias and Attenuation values further. Fine-tuning of these

controls will lead to excellent noise removal with few or no side-effects. However, the Duo is not

a magic wand, and it may not be possible to restore some badly degraded material beyond a

certain point. Experience will enable you to judge whether you have removed as much noise as

possible without unacceptable consequences.

Noise Reduction in M-S Mode

Our research has shown that it is sometime beneficial to perform noise reduction in M-S mode.

This means that, instead of adjusting the Level (or Bias), LF Bias and Attenuation values

independently for the left and right channels, you may adjust them for the monophonic content

within the signal (M) and for the content that is only present in the left or right channels (S).

Signal with a high Mid (M) noise component

If you perceive that the worst of the noise is coming from the centre of the stereo image, place

the auto dehisser in M-S mode. Now toggle the M-S button so that you are adjusting the S

component only, and reduce the Attenuation to zero. Toggle again so that you are adjusting the

M component only. You are now performing noise reduction on the centre of the stereo image.

Follow the tutorials above, and listen to the effect that this has. You will find that you can apply

a considerable amount of noise reduction on the M component without affecting the perceived

width or ambience of the wanted signal.

Signal with a high Side (S) noise component

Sometimes, you will find that loud, wanted signals in the centre of the stereo image mask the

noise, so that it is only noticeable at the sides of the image. Again, this can be handled

effectively in M-S mode. Toggle the M-S button so that you are adjusting the M component only,

and reduce the Attenuation to zero. Now toggle again so that you are adjusting the S

component only. You are now performing noise reduction on the sides of the stereo image.

Follow the tutorials above, and listen to the effect that this has. You will find that you can apply

a considerable amount of noise reduction without affecting the wanted signal at the centre of

the soundstage.

Содержание Auto dehiss

Страница 1: ...2004 CEDAR is a registered trademark of CEDAR Audio Ltd Duo declickle and auto dehiss are trademarks of CEDAR Audio Ltd E OE Subject to revision at the Company s sole discretion interstage Phistersvej 31 2900 Hellerup Danmark Telefon 3946 0000 fax 3946 0040 www interstage dk pro audio with a smile ...

Страница 2: ...CEDAR Duo declickle and auto dehiss This page left blank ...

Страница 3: ...g Started 7 Front Panel Indicators and Controls 8 General Set up and Connections 9 Memories 14 Remote Control MIDI Implementation 16 Declickle Removing impulsive noises 18 Declickle tutorial 20 An Introduction to Click and Crackle Removal 21 Auto dehiss Reducing broadband noise 26 Auto dehiss tutorials 30 A Short History of Noise Reduction 34 Licence and Limited Warranty 37 ...

Страница 4: ...CEDAR Duo declickle and auto dehiss ii This page left blank ...

Страница 5: ...ations in the Duo design and both units are intended for professional use Features include the following Flexibility Both Duo models handle a wide range of audio restoration requirements Portability Each Duo is a compact lightweight unit designed to fit a standard 1U rack space Audio interfaces Duos incorporate 96kHz 24 bit digital audio interfaces conforming to the AES EBU and SPDIF standards Pow...

Страница 6: ...ross Data format SPDIF or AES EBU Processor 400 Mflops peak Group delay milliseconds declickle processing auto dehiss processing 44 1kHz 190ms 463ms 48kHz 174ms 458ms 88 2kHz 95ms 461ms 96kHz 87ms 456ms In Bypass each unit has a latency of less than five samples irrespective of sample rate EMC Regulations In order to comply fully with EMC regulations a Duo should be connected using metal shelled c...

Страница 7: ... that the aforementioned equipment when used in accordance with the instructions in this manual fully conforms to the protection requirements of the following EC Council Directives on the approximation of the laws of the member states relating to n 89 336 EEC Electromagnetic Compatibility Applicable standards EN 50081 1 92 EN 50082 1 92 n 73 23 EEC Low Voltage Equipment Applicable standard BSEN 60...

Страница 8: ...DAR Audio USA 43 Deerfield Road Portland ME 04101 1805 USA Telephone and Fax T 1 207 828 0024 F 1 207 773 2422 Email cedarusa cedaraudio com Asian Office Address CEDAR Asia Mailing address Attention David William Robinson Tanglin Post Office PO Box 282 Singapore 912410 Telephone and Fax T 66 1 822 9227 F 66 2 619 1277 Email asia cedaraudio com Web Web www cedaraudio com Worldwide Dealer List For a...

Страница 9: ...with your CEDAR Duo please contact your local dealer or CEDAR office Alternatively you may send an email to support cedaraudio com In either case please provide the following details Your Duo hardware and software version numbers See General Set up and Connections A precise description of the problem All details shown in the status page Thank you ...

Страница 10: ... If it is used as a free standing unit the supplied rubber feet should be fixed to the base of the unit Power sources Each Duo features a universal power supply that will work safely on any mains supply in the ranges 85V to 260V 50Hz or 60Hz AC only The unit should always be grounded or earthed and power connectors should be routed so that they will not be walked on or pinched A Duo is connected t...

Страница 11: ...aging the carton should contain the following mains connection lead this manual rack mounting hardware four self adhesive feet Installation site To maintain reliability and prolong operating life observe the following environmental considerations the nominal temperature should be maintained between 5 and 35 Celsius relative humidity should be in the range 30 to 80 non condensing strong magnetic fi...

Страница 12: ... Screen soft buttons and spin wheel The set up and operation of the Duo is determined using the illuminated soft buttons and the spin wheel When a control or menu option is available the button alongside it will be faintly illuminated When an option is selected for adjustment the button alongside it will be fully illuminated Adjustment is carried out either by i repeated pressing of the illuminate...

Страница 13: ...you These are the Main screens for declickle and auto dehiss respectively To set up the unit and access a number of less often required parameters press the MENU option declickle main screen auto dehiss main screen auto mode auto dehiss main screen manual mode Menu You will now be presented with the MENU screen declickle menu screen auto dehiss menu screen ...

Страница 14: ...nit Setup Contrast Press the CONTRAST option and use the spinwheel to alter the contrast of the display to suit your viewing angle MIDI Channel Press the MIDI CH option and use the spinwheel to select the desired MIDI channel for remote control Reset Press RESET to reset the Duo to the factory defaults This will clear all user defined parameters and all the memories You will be asked to CANCEL or ...

Страница 15: ...ay the word CLIP if it detects digital overs Pressing the LEVEL button in this screen will reset the peak hold Bypass Press the BYPASS option to bypass the Duo s processing In this mode the Duo is 24 bit transparent The latency is reduced to less than 10 samples Close Press CLOSE to return to the Main screen Physical Connections Audio Your Duo offers two audio connection standards and passes its s...

Страница 16: ...h inputs are active when you switch on the Duo may not select the input you require so it is advisable only to present signal to one input at a time MIDI The Duo offers MIDI In Out and Thru These operate in the conventional manner Use MIDI to store and recall the memories and to control the Duo using external equipment See MEMORIES USB The Duo offers a USB socket This is for factory use only Statu...

Страница 17: ...is shows the measured sample rate of incoming audio and is accurate to approximately 0 01 This field is blank if the Duo is OFF LOCK DSPn NN NN mm This provides information about each of the SHARC processors within the Duo NN NN These are status codes that should be reported to CEDAR Audio in the event of a failure mm This field reports two messages OK or ERROR Close Press CLOSE to return to the M...

Страница 18: ...ns Mem xx The number XX shown here tells you which memory location is being addressed To change memory location press the soft button associated with this option and use the spinwheel to select other memories Store Press this to save the current workspace in the location MEM XX shown above Recall Press this to load the settings in MEM XX into the current workspace Rename When you press RENAME the ...

Страница 19: ...ticlockwise as appropriate If you do not choose a name for a memory it will be set to MEMORYXX by default If you clear a name and do not replace it the Duo will insert UN NAMED as the default Close Closes this screen and returns you to the Main screen Delete Deletes the contents of the current memory MEM XX Use this with care you will not be prompted to confirm the operation When the Duo is first ...

Страница 20: ...ories may be stored and recalled using MIDI patch change messages MIDI Controller Numbers All models Command CC Comments Bypass 16 0 63 Bypass OFF 64 127 Bypass ON Makeup Gain 17 0 127 maps to 10dB to 10dB Wordlength 18 0 31 16 bit 32 63 18 bit 64 95 20 bit 96 127 24 bit On Off 19 0 63 Processing OFF 64 127 Processing ON MIDI Controller Numbers Declickle only Command CC Comments Threshold left 20 ...

Страница 21: ...0 Atten B 27 0 127 maps to 0 0 to 40 0 Auto mode on off 28 0 63 Auto mode OFF 64 127 Auto mode ON Patch change messages Ordinarily a patch change message Patch NN causes the user memory of the corresponding number NN to be recalled There are 99 user memories and patch numbers outside the range 1 99 are ignored except for the following special cases Sending Patch 0 causes the audio parameters to re...

Страница 22: ...set high Declickle will remove only the largest clicks and scratches A lower threshold will also remove smaller ticks clicks and crackle If you reduce the value too far the wanted audio may exhibit mild damage in the form of a slight instability in the background signal You should therefore always attempt to find the highest value at which the unwanted noise is removed The threshold ranges from 00...

Страница 23: ...nd will maintain the brightness of the original signal Use it for removing clicks from high bandwidth signals such as obtained from high quality vinyl and signals recorded directly to digital media medium A compromise between fine and coarse settings this is the most commonly used mode coarse Designed to detect rounded grungier clicks and crackle this mode will detect more problems but with a grea...

Страница 24: ...t if you notice any dullness or distortion If you reduce the threshold too far the wanted audio may exhibit mild damage in the form of a slight instability in background sounds and any background noise present You should always attempt to find the highest value at which the unwanted clicks and crackle are removed The correct threshold will vary with the detector mode chosen Fine mode will require ...

Страница 25: ...witches between them as appropriate This removes large clicks but like all non digital solutions is unable to distinguish small ticks from genuine signal Also the switcher assumes a perfect monaural source If the groove walls differ significantly or suffer degradation simultaneously then the assumption and therefore the restoration fails Digital technology has made it possible to implement ideas t...

Страница 26: ...polation takes account of two adjacent good samples and the elapsed time between them In this algorithm the corrupted data is replaced by a straight line joining the last good sample and the next available good sample The result is less offensive than Sample and Hold but suffers from low frequency artefacts and a reduction in audio bandwidth over the interpolated region ...

Страница 27: ...ce is the cause of several common signal defects If the disturbances are randomly distributed the degradation will sound like crackle or a chip fryer type of noise If they are regularly spaced the degradation will sound like a buzz Alternatively if they are correlated with the signal the degradation will sound like distortion Declickle will correct all of these problems so the term crackle removal...

Страница 28: ...CEDAR Duo declickle and auto dehiss 24 Various Forms of Crackly Signal Defects ...

Страница 29: ...dered to be additive and this assumption is no longer appropriate Declicking a crackly signal discards a lot of useful information that an optimal algorithm can use to improve the quality of the processed audio Declickle CEDAR s Declickle algorithm was born out of research into the dual problems of declicking and decrackling difficult signals such as those including overblown brass instruments sol...

Страница 30: ...n Mid Side format whilst retaining conventional Left Right stereo at the input and output Switching between Modes You may switch between modes using the front panel buttons as follows Auto Manual Toggle between AUTO and MANUAL modes by pressing and holding the AUTO OFF MANL OFF button for three seconds or more This operation is also available in the MENU PROCESS MODE screen Left Right Mid Side Tog...

Страница 31: ...se reduction to a wide variety of audio material The Bias control is a multiplying factor that affects the noise level calculated during the course of the signal It is not the same as the Level control in Manual mode which sets an absolute value for the noise content of the recording LF Bias dB at 0Hz The LF Bias control allows fine control of the algorithm below 5kHz It has no effect on higher fr...

Страница 32: ...L modes You may press the BYPASS button in the Audio I O page to cancel Bypass Manual Mode In Manual mode the Bias control is replaced by a Level control and the AUTO OFF button becomes MANL OFF All other controls operate the same way as they do in Auto mode There are six options LEVEL LF BIAS ATTEN L R M S shown above in L R mode MENU MANL OFF Level dB The Level control allows you to determine th...

Страница 33: ... applied at any given frequency at any given moment If the algorithm determines that the noise attenuation at any moment should be less than the ATTEN that you select the lesser figure will be applied L R M S Select which channel or channels you are adjusting by repeatedly pressing the L R M S button Toggle between Left Right and Mid Side modes by pressing and holding this button for three seconds...

Страница 34: ...ial Your first task will be to find the most appropriate setting for the Level This will be the biggest influence on the quality of the processed signal Starting with the Level at zero and the Attenuation at 40dB increase the value of the Level At first you will notice very little happening Next you enter a region in which there may be noise bursts and an artefact similar to noise pumping Increase...

Страница 35: ...u can now adjust the Attenuation to determine the amount of noise removed Decrease the amount of attenuation from 40 0 to 0 0 at which point you will hear that the processed signal is identical to the unprocessed signal This is because the Attenuation control is limiting the amount of noise removal to 0dB i e there is no effect Now increase the amount of Attenuation as defined by the material and ...

Страница 36: ...s action to accommodate broadband noise with differing frequency characteristics Your Duo allows you to do this by accentuating or suppressing the amount of noise identified at low mid frequencies Switch the processing off and listen to the source material Does the noise appear to be present at all frequencies If not is it predominantly high frequency hiss or low frequency rumble If the former tur...

Страница 37: ... independently for the left and right channels you may adjust them for the monophonic content within the signal M and for the content that is only present in the left or right channels S Signal with a high Mid M noise component If you perceive that the worst of the noise is coming from the centre of the stereo image place the auto dehisser in M S mode Now toggle the M S button so that you are adju...

Страница 38: ...de of the noise by say 6dB you also reduce the desired signal by the same amount So the low pass filter will clean your antique 78s which have little or no high frequency content but even then only at a cost Dynamic Filters are devices in which the cut off frequency moves dynamically according to the signal content thus removing high frequencies when there is no signal present but leaving them unt...

Страница 39: ...f the noise you remove 3 4 of the signal and so on Consider now a signal that has at a given frequency 100 units of volume on an arbitrary scale By measuring the noise content of that signal during an otherwise silent passage you can determine that there are say 20 units of noise present at that frequency It should be possible to remove this noise by removing 20 of the signal But what if a moment ...

Страница 40: ...oise level attenuation and a third parameter called brightness or variance However this method is not what we mean today when we use the term auto dehissing In our search for a truly automatic dehisser that you can set up and forget we have devised an algorithm that without human intervention performs a remarkably good job of identifying the noise content of any signal presented to it To use this ...

Страница 41: ...any and all copyright trade marks trade names styles and logos and other intellectual property rights in the System including all documentation and manuals relating thereto are the exclusive property of the Company The Licensee acknowledges that all such rights are the property of the Company and shall not question or dispute the ownership of any such rights nor use or adopt any trading name or st...

Страница 42: ...r offered for supply by the Company or which the Company certifies has been superseded by a later version or has become obsolete 5 FORCE MAJEURE The Company shall not be liable for any breach of its obligations here under resulting from causes beyond its reasonable control including but not limited to fires strikes of its own or other employees insurrection or riots embargoes container shortages w...

Страница 43: ... provided by the Company or for any other indirect or consequential loss 11 ENTIRE AGREEMENT The Company shall not be liable to the Licensee for any loss arising in connection with any representations agreements statements or undertakings made prior to the date of supply of the System to the Licensee 12 TERMINATION This Licence may be terminated forthwith by the Company if the Licensee commits any...

Страница 44: ...Date Manufactured by CEDAR Audio Ltd 20 Home End Fulbourn Cambridge CB1 5BS UK Web www cedaraudio com Email info cedaraudio com Tel 44 1223 881771 interstage Phistersvej 31 2900 Hellerup Danmark Telefon 3946 0000 fax 3946 0040 www interstage dk pro audio with a smile ...

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