user manual - ClickRepair
Contents
1. AC t od P u lt gt 4 t gt EAA be oy A t y Org ne gt wre lypet a a tos lt sn A Click Start to begin Progress will be indicated as in the picture above 4 More advanced use Features in common with ClickRepair amp DeNoise Equalizer works in exactly the same way as ClickRepair and DeNoise If you have not previously used either of those applications you should download the ClickRepair manual and consult the following chapters e Chapter 4 Producing and Organising files e Chapter 5 User Interface Basics e Chapter 7 Audio Monitoring and the Sound Buffer e Chapter 10 Batch Processing e Chapter 11 The Preferences Dialog The reason that so much of the operation is in common is that about 70 of the code base of the three applications is identical This means that enhancements to one of them will apply to all of them It also means that I decided not to repeat those chapters in this manual Main Controls The Open Play and Abort button are inherited from the other applications Once a file is open this button will change to Start While processing is in progress it will change to Pause Pressing the space bar or clicking the button will pause operations and the button will change to Resume The Play button will play the samples which are selected in the upper narrow window the Sound Bar Changing any of the Filter2. Because it is electronic equipment it is subject to the fundamental physical law of causality This technical term is a statement of the simple fact that the output of the amplifier at any instant can depend only on the input up to that instant The law of cause and effect Any equalizer which is realised in electron ics is subject to this fundamental law one of whose consequences is this the phase response of a causal filter is completely determined by the amplitude response Digital Signal Processing DSP can easily circumvent this law by reading ahead Of course that does not violate causality but it does introduce latency since the output at a particular instant will now depend on future as well as past samples and cannot be computed until those future samples have been read This can be useful but it also introduces an Achilles heel A DSP equalizer de signed to reproduce a particular equalization standard normally specified as a frequency dependent amplitude response can have almost any phase response whatever Even worse it turns out that it is very difficult indeed to reproduce the phase response of an electronic filter because the original continuous signal has been replaced by discrete time samples I wrote Equalizer as an application able to perform high quality emulation of analogue filters in its phase response This is particularly 1 The Kramers Kronig relation useful if you are removing an existing RIAA equalization and
3. and a narrow window at the top for navigating and selecting sample for playback o a ot M vat Uh Da m 7 a mre lt gt t gt r 48 no i t y gt Ff vw a i am I myne ee wwe iper A second window will also appear provided that the Display check box bottom right is se lected as here The information it displays is described later If this window is not visible make certain that the Display check box is selected and that it is not behind the main window The position of windows is persistent from one session to the next Simple settings For the purpose of this quick start I assume that you have captured a Decca ffrr LP record using equipment which has applied RIAA equalization Looking at the main window it is seen that the Original pop up menu drop down list on Windows has been set to RIAA so as to undo the existing equalization and New has been set to ffrr LP The effect of this is seen in the Gain Curves window The red curve is the inverse RIAA equalization the green curve the Decca ffrr LP equalization I left the Lo cut and Hi cut filters switched off and the Gain control set to OdB As a result the blue curve which is overall equalization to be applied is simply the difference between RIAA and Decca ffrr LP The difference is significant and will have a noticeable effect of the perceived brightness of the recording Because Equaliz
4. replacing it with one which is correct for the actual record Speed issues If a 78 rpm record is captured using playback at 33 rpm or 45 rpm then the sample rate aka pitch will have to be adjusted using your audio editor As an example suppose that a 78 rpm record has been captured at 45 rpm at a sample rate of 44 1 kHz Then you should change the sample rate to 76 44 kHz 44 1 kHz multiplied by 78 45 without resampling More information including a how to for some of common audio editors is gtven in Appendix B The reason for not resampling is that you actually want the same audio samples to be played at a faster rate you do not want them to be changed in any way Of course you may have to subse quently resample to 44 1 kHz in order to produce a CD This replaces the 76440 samples of each second of audio by 44100 newly computed samples so that the playback speed is not changed while the audio file becomes smaller A problem arises immediately if the original capture also applied RIAA equalization Such equaliza tion will be affected by changing the pitch RIAA equalization is specified by three turn over fre quencies To see how this interacts with the speed change imagine that a 78 rpm record has on it a pure note at the frequency of 1 kHz If this record is captured at 78 rpm using RIAA equalization then the audio file will also contain a pure note at 1 kHz and there is no problem working out what point of the R
5. settings during such playback will have no effect on what is heard once samples are processed and in the buffer they cannot be changed other than by restarting What is played is determined by selecting the Sound Group In and Out radio buttons The effect of changing the Mono Mix settings will be heard during playback this effect is only applied as the samples are exported from the buffer and written to file When Merge is selected the and buttons will be enabled This is of assistance in selecting the optimum balance setting for mono mix down See below Processing stopped Abort Startagain Continue The Abort button can be used to terminate processing of the current file completely or as a way to restart processing using different settings It produces the dialog above to indicate that The Filters Four filters and an overall gain control are available I will describe each in turn showing their ef fect by providing pictures of gain curves at each stage If you with to follow this set all filters to Flat or Off and set the Gain control to 2dB The gain will display as a blue line at 2dB from 20Hz to 20 kHz The settings I am using here were used as the first stage of processing the 1925 Percy Grainger sample which is on the website The record was captured at 45 rpm through a pre amplifier with built in RIAA equalization at a sa
6. Equalizer 1 9 www kagi com clickrepair for Java enabled platforms Information and Instructions Brian Davies clickrepain Okage COM Preamble Please Read In 2004 I began to write software for removing clicks heard on typical LP recordings once they have been captured for transfer to CD The resulting application ClickRepair now has a wide circle of users from whom I have received much encouragement Equalizer is part of an expansion of that software to other areas of audio restoration particularly audio captured from older records It is free software Equalizer is written in Java and developed using X Code an integrated development environment that ships with every copy of Mac OS X The Windows installer is produced using Inno Setup 5 by Jordan Russell The manual is produced using Apple s Pages application and typeset in Garamond I wish to thank those users who have contributed to the design of the Interface I owe a particular debt to Michel Poulain and Willy Kunz who spent many hours working on the French and German translations Table of Contents Introduction Basics Phase issues Speed issues Installation Apple Mac OS X Microsoft Windows Quick Start Initial Interface Simple settings Processing the file Main Controls The Filters Custom Equalizers Mono Records Appendix A Equalizer Settings Appendix B Sample Rates amp Resampling Changing Sample Rates Resampli
7. IAA curve was used by the amplifier But if the record is played at 45 rpm the note will be heard and captured as a 577Hz tone and this is what will pass through the amplifier per forming the RIAA equalization After you change the sample rate of the file to 76 44 kHz the note will once again play at 1 kHz but it will still have been equalized as for a note at 577Hz The RIAA standard is that a 1 kHz note is left unchanged whereas some boost will have been applied by the amplifier at 577Hz and must be removed as part of the editing process To help adjust for these problems Equalizer has four built in inverse RIAA equalizers designed to remove the equalization They are e Normal for records captured at the correct speed using an RIAA equalized pre amplifier e Frequency shifted for 78 rpm records captured at 33 rpm and 45 rpm and for 45 rpm records captured at 33 rpm using an RIAA equalized pre amplifier Note that capturing a 78 rpm record at 33 rpm may introduce severe rumble problems since turntable noise originally in the range 15 30Hz will be shifted to 35 70Hz clearly audible 2 Equalizer does not do this gt Not all resampling algorithms are equal some can introduce serious audible degradation Make certain that your software uses good and probably licensed under patent methods 4 2 Installation Apple Mac OS X Users should download the file Equalizer dmg Upon double clicking the file it will mount as
8. a vol ume The contents should be dragged to the desired location on your hard disk most likely the applications folder Equalizer for Mac OS X require a Java run time and have been tested on Mac OS X 10 3 to Mac OS X 10 7 The latter version Lion does not have Java pre installed but a Java run time is available from Apple you will be prompted to install it the first time you attempt to run a Java application The situation with the upcoming Mac OS X 10 8 is unclear visit my website for information which will be posted when it is available There is no installer for Mac OS X I recommend that you create a folder Equalizer in your Ap plication folder and keep the applications and the manual in it For easy access drag the Applica tion icons to the dock as well Microsoft Windows Microsoft discontinued Java deployment for Windows some time ago Equalizer users should download and run the installer EQinstall exe which does not come with a Java run time You will be prompted to install one if necessary The applications have been tested with Java 1 6 on both Windows XP and Windows 7 Shortcuts to the Application and to the Manual are installed in the Windows Start gt Programs menu at Start gt Programs gt Equalizer 3 Quick Start Initial Interface On starting Equalizer the default window has the appearance shown below There are four groups of controls a large window in the middle for viewing the the waveform
9. e walls But for normal use it is best to attempt to keep only the horizontal signal This is achieved by first setting the balance to OdB and then gently moving the slider by a fraction of a dB at a time listening for the musical content to be at a minimum For this particular recording that point was achieved by setting the gain of the right channel at 0 8dB above that of the left Provided the sound buffer is not yet full clicking resume is all that is needed to apply this setting to the whole file The merge is applied as the audio is exported 12 Appendix A Equalizer Settings Most records ate mastered with some attenuation of the bass at 6dB octave and in many cases with some increase in treble at 6dB octave This requires the specification of two turn over fre quencies Often there is a third low frequency turn over below which bass cut ceases It is usual to specify equalization relative to OdB at 1 kHz So for example the standard RIAA LP was recorded using treble boost from 2 1215 kHz up and bass cut from 500 5 Hz down to 50 5Hz below which the theoretical level is 20dB On playback these recording levels need to be reversed The 12 pre set equalization curves built in to Equalizer have the following turn over frequencies They are not user adjustable and are given here as a convenient reference only comers ff e oo e o ome o S a y a per e e oo e e e o w o S e y ES a a a a Most of these equalizatio
10. eo car tridge They can be mixed down to mono by ClickRepair using an automatic balanced merge algo rithm available in that application but they can also be mixed down to mono using the Equalizer application A simple reason for recommending an initial stereo capture is that it is quite common that the output from the two channels first from the cartridge itself and then after passing through the pre amplifier may not be exactly balanced For the purpose of this section 1 opened the Percy Grainger file and selected the Merge check ce box before starting Since this is not a vertical recording I left the R invert right channel check box un checked The I started processing pausing after the sound buffer was nearly full Fi co 22 nally I selected a few seconds of audio in the Sound Buffer at the top checked the radio but ton and the Loop check box I y eT i ia i a Lael Regt OW are vy gag wn gh bigger re i s Marap K gt re I _ es Awi A cra n t yore a p n A vamer aa haahi Dt anii TT nae bee Wee ot x Hee Mes a ww Ch oad Serle Q 4 2 5 ALJ Da 6 of it saj aoe The result of this is that once I clicked Play and endless loop of mainly noise was played Mov ing the balance slider completely to the left or right results in the audio from only one channel be ing used This is basically what is being picked up from one or other of the groov
11. er pays attention to the phase response of these operations the result should match quite closely that which would have been obtained using an amplifier equipped to play Decca ffrr LPs Processing the file Equalizer is based on the same framework as ClickRepair and DeNoise It is not an audio editor and it will not change an existing file To equalize an audio file first use the Open button which will bring up a file selection dialog for the file to be processed followed by a second dialog for naming the new file The default is that if you choose the file beethoven aiff then the suggested name for the new file will be beethoven eq aiff An alternative is to use Drag and Drop which is new to Equalizer 1 6 The convention for naming the newly created file and the choice of folder where it goes is determined on the basis of the preference settings A dialog will appear showing the full path name of the output file The Open button will now change to Start Before clicking it choose one of the options in the Sound Output group e Out to listen to the sound after equalization e In to listen to the untreated sound e Off not only turns off the sound but will increase the speed of processing from real time to whatever the processor can achieve This selection may be changed during processing b em i nah bata kd t eet Mee ot ww been Mees ot Seed Chet owt e Dy a Paste
12. esample e In Cool Edit Pro or Adobe Audition for Windows go to the Edit gt Adjust Sample Rate menu item and change the sample rate e Note in Adobe Audition use the Edit gt Convert Sample Type menu item to resample the audio Resampling An audio file at a sample rate of say 76 44 kHz is quite unorthodox If the end use of this file is for conversion to a compressed format such as mp3 or aac this is not an issue But if the file is to be subsequently burnt to disc in standard audio CD format the file will have to be resampled to the CD rate of 44 1 kHz Clearly this is a complex re calculation because each 76440 samples to con tinue with the same example must be interpolated using a suitable mathematical algorithm to yield just 44100 samples which represents the same sound This is a highly complicated procedure In principle audio sampled at 76 44 kHz carries information up to 38 22 kHz In practice there will be no problem converting these samples to an analogue signal with negligible errors in the full frequency range 20 Hz 20 kHz By contrast it is only with a high de gree of sophistication that CD quality sampled audio can be so converted which is why all CD players are not equal This applies also to digital resampling not all algorithms are equal Because the number of samples is adjusted to match the change in sample rate resampling does not affect the pitch and so does not affect the choice of equalizer setti
13. mple rate of 44 1 kHz Since the original record was designed to be played at 80 rpm I then changed the sample rate to 78 4 kHz without resam pling see Chapter 1 and Appendix B First the RIAA equalization must be removed by selecting RIAA 45 gt 78 in the drop down menu Since RIAA equalization consists of boosting the bass and cutting the treble the inverse curve has the appearance here The red curve is the inverse RIAA equalization Notice that it is not OdB at 1 kHz because of the pitch change The blue curve is the overall gain of the process cur rently 2dB above the single filter chosen so far Next we need to apply equalization appropriate to the actual recording I chose HMV Blumlein for this to get the following result Detailed information about the 12 pre set equalizer filters is given in Appendix A gt http www kagi com clickrepait Given the extent of processing needed for restoration 78 is close enough to 80 for this purpose The red curve remains as before but now there is a green curve to show the effect of the HMV Blumlein filter The blue curve is the sum of the two and the 2dB of extra gain I applied You can see that I used it to bring the equalization at 1 kHz back to about zero The third filter is a low cut filter Technically it is second order Butterworth filter There is no audio content on this record below 40 50Hz so I chose a cut off of 32Hz for safety The effect of this fil
14. n settings were inspired by those available in the Elberg MD 12 profes sional pre amplifier except that I used the bass turnover frequency of 300Hz for ffrr 78 and the treble turnover of 3 4 kHz for Decca 78 taken from Roger Wilmut s website For convenience I also added the EMI LP system 13 Appendix B Sample Rates amp Resampling The audio formats supported by Equalizer are of AIFF and WAV types These formats are very similar in that they consist of a number of small header chunks containing information about the number of channels the sample rate the sample type etc followed by the bulk of the file which is the audio data itself This data is always in the form of a sequence of numbers represent ing samples taken at equally spaced time intervals in a specified format such as 24 bit integer Changing Sample Rates If the sample rate which is a single number contained in one of the header chunks is changed for example from 44100 to 76440 the only effect is to change the speed at which the audio will be played using a computer program Typical ways to change the sample rate are e In Sound Studio for Mac go to the Audio gt Change Sample Rate menu item which brings up a dialog Enter the desired new sample rate then de select the checkbox Resample Audio In Amadeus for Mac go to the Sound gt Characteristics menu item enter the desired new sample rate then select the checkbox Don t r
15. ng WKB LK amp yn a Ut S PON DAD AW 13 14 14 14 1 Introduction Basics Equalizer is an application designed to assist when capturing and restoring audio from gramophone records The most common situation is that the record is a normal stereo 33 rpm vinyl record and that it has been captured via an amplifier preamplifier which performs RIAA equalization elec tronically In this case Equalizer is not required nor even useful There are however many situations where the equipment used for audio capture does not match the equalization required for the original record The ideal solution is to buy a special purpose pre amplifier Another is to capture the record to an audio file using the equipment at hand then sub stitute the inappropriate equalization with the correct equalization as a digital process That is what the Equalizer application is designed to do There is a further issue when working with older 78 rpm shellac records the question of turntable speed Many hobbyists simply do not have and do not wish to purchase a good quality turntable offering 78 rpm Often this is because they already have good quality equipment which will play 33 and 45 rpm records There are also some people who prefer to capture a 78 rpm record at 45 rpm because it can offer advantages such as better tracking stability Phase issues Electronic equipment deals with audio as a continuous electrical signal in real time
16. ngs For the purpose of noise reduction however I recommend that the resampling be deferred until after any use of pro grams such as ClickRepair for clicks and crackle and DeNoise for hiss and broadband noise 14
17. ter is now evident in the Gain Curves window from about 50Hz down as a cyan coloured curve The effect is also factored into the blue curve The fourth and last filter is a high cut displayed in orange This is again a Butterworth filter and there is a choice between first order 6dB octave or second order 12dB octave Based on my auditioning of the material I judged that there was no point having a cut off greater than 8 kHz or a lower roll off rate The issues to consider in making such a decision are as follows e Simple linear filtering like this does not introduce processing artifacts which can be distracting e Simple linear filtering affect everything so it should not be overdone e Subsequent denoise operations are better suited to reducing the remaining hiss 7 It emulates an electronic filter which is not the same as a second order DSP filter of the same name 10 So here finally is the filter which I applied to the Percy Grainger record I did this before any noise reduction processing Then I de clicked then de crackled and merged then finally reduced the hiss Custom Equalizers In addition to the 12 preset equalizers described in Appendix A in the New menu there is pro vision to add custom equalizers To do so select the Custom item on the menu which will bring up the dialog shown here Delete er UF New Dquslizer Narre my Hegh Frequercy 909 He Midde Frequercy yo Ma Low requesc
18. y 160 He There are four fields two of which must contain data the name and the middle frequency The other two fields may be left blank indicating that there is no corresponding turnover frequency 8 The restrictions on the allowed entries are e The name must be no more than 32 characters long and not match that of a Default Equalizer e The middle frequency must be between 100Hz and 5000Hz e The high frequency must be between 1500Hz or the middle frequency if that is higher and 10000Hz or it may be left blank e The low frequency must be between 20Hz and the middle frequency or it may be left blank 8 In previous Equalizer versions the middle frequency was called bass turnover the other two treble and lower bass turnovers The new version of Equalizer can be used in conjunction with direct input from tape heads which require a middle frequency of 4000Hz for which the nomenclature bass is inappropriate 11 While these adjustments are being made the corresponding gain curves will be displayed whenever the entries are in acceptable limits the Save button will be enabled Existing custom settings may be deleted using the Delete button and the menu alongside Preset equalizers may not be deleted or otherwise edited although their turn over frequencies are dis played for convenience Mono Records I recommend that mono recordings be captured in stereo if the cartridge in use is a ster
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