User Manual


BitPerfect is a high-quality music player for 64-bit Intel Macs running OS X 10.7 and upwards (Lion, Mountain Lion, Mavericks, Yosemite, El Capitan, or Sierra).  BitPerfect integrates with iTunes to improve sound quality.

BitPerfect now supports native playback of DSD files.  Those of you who are familiar with DSD will already know that, as is the case with FLAC files, the problem is that you cannot import native DSD files into iTunes.  To resolve this problem, beginning with BitPerfect v2, BitPerfect now supports “Hybrid-DSD” files which can be imported into iTunes.  With these “Hybrid-DSD” files, and a DAC capable of supporting DSD playback, BitPerfect will now play DSD music seamlessly.  There is an entire section on DSD playback at the end of this User Manual.  It is extremely important that users who wish to enable BitPerfect’s DSD support should read this section of the User Manual carefully.

If you ever encounter any problems with BitPerfect, please send an email to (support only available in English).

This manual applies specifically to the v3.1 release of BitPerfect, but is generally also applicable to previous versions.

Getting Started

BitPerfect sports a very simple, unobtrusive interface.  When you run BitPerfect, look for a small, black BitPerfect icon in the top right corner of your screen, near the date and time.  This is what we refer to as the "Menu Bar Icon."

BitPerfect comes pre-configured with sensible defaults for most users.  To start using BitPerfect, simply run the program, find and click the Menu Bar Icon and go to "Preferences".  From here you can choose the audio device you would like BitPerfect to use from the drop-down marked "Audio Output Device".  Note that if you wish to choose an external audio output device which has been temporarily disconnected or switched off, then it may not appear on the list.  Re-connect the device, switch it on, and then close and re-open the Preferences menu.

As soon as you start playing music in iTunes, BitPerfect takes over control of the audio playback.  While BitPerfect is playing music, it assumes exclusive ownership of the device it is using (so-called "hog" mode).  This means that other Apps (Browsers, Movie Players, etc...  even OS X itself) will not be able to output sound through that device until BitPerfect releases control.  When BitPerfect has taken control of an output device, its Menu Bar Icon changes to green.  To release control, either stop or disable BitPerfect.  Both of these actions can be accessed by clicking the Menu Bar Icon.

You still use iTunes to direct all the usual aspects of playback, such as pausing playback, or moving the track position slider forwards and backwards as you require.

Menu Bar Icon

BitPerfect’s Menu Bar Icon has two functions.  First, its appearance tells you something about the state of BitPerfect.  It is normally black in colour (or white if you use OS X's "Dark Mode").  When BitPerfect is actively in control of audio output, it changes colour according to the audio format of the music being played.  This is discussed in more detail later.  If you disable BitPerfect this icon turns grey.  Second, clicking on the Menu Bar Icon causes a drop-down window to open up, and allows to access various features of BitPerfect.  From top to bottom, these are:
  • The top line is for information only, and shows the status of BitPerfect.  It will either say “Stopped”, or “Playing …” followed by the audio format currently being played.  If "Integer Mode" playback is active this will be indicated by "[ I ]".
  • About opens a window showing some brief information about BitPerfect, including the Version Number.
  • Change Music Directory opens the Access Permissions dialog (see below).
  • Launch iTunes and Quit iTunes allow you to manually launch and quit iTunes.
  • Stop causes both iTunes and BitPerfect to enter the Stopped state.  iTunes will stop playing the currently playing track, and BitPerfect will relinquish control over the audio output device.
  • Disable BitPerfect and Enable BitPerfect allow to disable and re-enable BitPerfect.  This can be useful for comparing the sound with BitPerfect in or out of the playback loop.  Note that Disabling BitPerfect also necessarily causes both BitPerfect and iTunes to Stop, so comparisons cannot be done “on-the fly”.
  • Audio Output Device is a shortcut that allows you to select BitPerfect's audio output device, as discussed more fully in a separate section below.
  • The volume control slider allows you to separately access any volume control functionality built into the audio output device, such as the Built-In Output or an external DAC.  Not all devices support volume control, and if so this control will be either greyed out or non-responsive.  The “Adjustment” number refers to a volume override in the comments field of the track currently playing (see below).  It can also refer to a Sound Check volume adjustment number (see below).
  • Preferences… opens BitPerfect’s Preferences Window.  This is described in great detail below.
  • Device Info… opens the Device Info Report window.  This information is very useful to BitPerfect Support in the event that you have a problem to report.
  • Quit BitPerfect causes BitPerfect to quit.

Access Permissions

Apple has introduced strict requirements for Apps to be sold on the App Store.  Amongst other things, these require us to ask for your explicit permission to read certain files on your computer.  Obviously, we need to read your music files in order to be able to play them.  Apple requires that we seek those permissions in the following manner.

Starting with BitPerfect v3 the procedure for managing Access Permissions has been significantly streamlined.  However, it in turn requires strict adherence by the user to these instructions.

When BitPerfect launches for the first time, provided you have not previously granted Access Permissions using a previous version of BitPerfect, it works with iTunes to determine a common root folder below which all of your music files can be located (this may take a few minutes if you have a very large library).  It will then open a Finder window to that folder and give you the option to Open or Cancel.  If you select Open, it will then correctly set your Access Permissions.  If you select Cancel you will fail to set Access Permissions and BitPerfect will fail to operate.  If you navigate away from this folder before you click Open, you will suffer unpredictable results.  On some versions of OS X this folder may open up behind iTunes and as a result may not be immediately visible.  After you click on Open, a dialog box will appear confirming that your music library has been updated.

If at any time you add additional files to your iTunes Library, located in a folder to which these access permissions have not previously been granted, BitPerfect will not be able to play those files.  To fix this, you can re-run the permissions dialog at any time by selecting “Change Music Directory” from the BitPerfect menu bar menu.  Please note that this only affects users who have specifically set up iTunes to have their music files managed by the user.  If you are uncertain, look in iTunes’ Preferences, under the Advanced section – if you have checked “Copy files to iTunes Media Folder when adding to library”, then you will not have to worry about this.

When you select “Change Music Directory” the process is the same as described for first-time launch.  However, if as a result BitPerfect determines that the Access Permissions do not need to be changed, then the folder described above will not be displayed.

If you play tracks for which Access Permissions have not been granted, these will be played by iTunes, not BitPerfect.  You will observe that BitPerfect’s menu bar icon will stay black.  BitPerfect’s menu bar icon shows green (or some other color - see below) when BitPerfect is controlling playback.


If you are using OS X 10.8 (“Mountain Lion”) or higher you will have the ability to use BitPerfect to play music through an AirPlay device.  There are, however, some limitations to BitPerfect’s ability to support AirPlay due to the way Apple has elected to configure the interface.  AirPlay allows multiple devices to operate off the same AirPlay interface (for example, Airport Express and Apple TV).  Users can normally select between these devices both from within iTunes and using the Audio Midi Setup console.  However, Apple does not permit BitPerfect to make this selection.  To compound this problem, the way the AirPlay device responds is different depending on whether you are using iTunes or a third-party App such as BitPerfect.  What you will find is that when you use BitPerfect to play through AirPlay, it will only direct sound to the one AirPlay device selected in the Audio Midi Setup console.  Changing the selected device within iTunes will have no effect on BitPerfect.  We hope Apple will rectify this behaviour in a future OS X update.

With OS X 10.9 ("Mavericks") there are further subtle differences.  Here is the current thinking about how to make AirPlay work with BitPerfect under Mavericks:
  • First, you must select AirPlay as the audio output device in BitPerfect, then quit BitPerfect.
  • Then, go into Audio Midi Setup and select the AirPlay device you want to play through (such as AirPort Express).
  • Now, go into iTunes, and in the AirPlay configuration utility select Computer.
  • Finally relaunch BitPerfect.
  • While all this is happening, make sure you have no other devices in your house using AirPlay.  You may have to repeat this cycle multiple times until the settings remain stable (I do not know why that is).

With OS X 10.10 ("Yosemite") the above process still works, but now there is no need to quit BitPerfect after selecting AirPlay as the audio output device.  Experience seems to show that AirPlay playback is significantly more stable and reliable under Yosemite.

AirPlay has changed very dramatically under macOS Sierra (10.12).  On the one hand, Apple is definitely moving in the right direction with the changes the first introduced with OSX 10.11 ('El Capitan').  But on the other hand, they have introduced a whole set of new problems that they (and we) are going to need to work through.  With macOS Sierra, though, things are starting to improveOriginally, the AirPlay device was treated by OS X as a standard audio device interface, which BitPerfect could select like any other audio device.  However, behind the interface, the AirPlay subsystem has many capabilities which the Standard Audio Interface is not designed to handle.  With El Capitan, and now macOS Sierra, instead of AirPlay being a single device, each of the individual AirPlay devices now appears as a separate entity in OS X’s system sounds.  Unfortunately - and this is one of the big problems - AirPlay devices do not appear at all in BitPerfect's list of available Audio Output devices unless one of the AirPlay devices has been selected as OS X's default audio output device.  Consequently, in order to use Sierra’s AirPlay under BitPerfect, the procedure appears to be as follows:
  • First, go into System Sounds and select as the Default Audio Output device the specific AirPlay device that you want to play to.
  • Next, in iTunes, click on the icon to the right of the volume control slider and make sureComputer is selected.
  • Finally, from the Audio Output Device section of BitPerfect's menu bar drop-down menu (or, if you prefer, from the General tab of BitPerfect's Preferences Window), select your chosen AirPlay device, which will now appear in the list of available devices.
However, be aware that you as the user, or even other Apps, can select a different AirPlay device as OS X’s default audio output device.  If that happens, the currently-playing device will suddenly no longer be available to BitPerfect and it will simply stop playing. If you get intermittent disconnects to your AirPlay device (a significant issue with Wi-Fi) this can also cause unpredictable problemsExperience seems to show that AirPlay playback is significantly more stable and reliable under Sierra than El Capitan.  There is not much to choose, stability-wise, between Sierra and Yosemite, except that Yosemite obviously has a longer track record.

**Please read the AirPlay section once more to be sure you understand it, if you plan on using AirPlay**

DRM, Streaming Music Sources, Home Sharing & Apple Music

BitPerfect cannot support Streaming Music Sources such as TIDAL, Spotify, Home Sharing, or Apple Music.  This is because BitPerfect needs to receive from iTunes the full path and name of the music file in order to be able to load it into memory.  With a Home Sharing network, iTunes does not supply BitPerfect with an accessible file path - BitPerfect cannot therefore load the file, and so it returns playback responsibility to iTunes.  With TIDAL, Spotify and Apple Music, music is streamed from the Cloud – so there is no file anywhere for BitPerfect to load.  When using any of those services, even if BitPerfect is running, it will be iTunes that is playing the file (the BitPerfect Menu Bar Icon will be black).

Also, BitPerfect does not support files containing Digital Rights Management (DRM).  These tend to be older files downloaded from Apple, and usually have the extension ".m4p".  However, files downloaded from Apple Music for off-line listening also contain DRM and are not supported by BitPerfect.

Volume Control

There are two ways to use iTunes and BitPerfect to control the playback volume:
  1. The iTunes volume control continues to function normally.  When BitPerfect is playing, it uses the setting on this slider to perform digital volume control inside its own playback engine.  This volume control will not have any effect if BitPerfect is playing native DSD content.
  2. BitPerfect also has its own volume control slider in the drop-down menu from the Menu Bar Icon.  This slider uses your DAC's own built-in volume control.  However, some DACs do not support internal volume control, and in these cases this slider will be disabled.  (Note:  Some DACs tell BitPerfect that they support internal volume control, but then fail to do so.  In such cases BitPerfect's volume control slider will function, but will not affect the volume).

Menu Bar Icon Color

The menu bar icon is normally black in color (or white if you use OS X's "Dark Mode").  However, when BitPerfect is in control of playback the icon changes color.  With previous versions of BitPerfect this color was always green, but starting with v3 the color indicates the format of the audio stream being played.  This is only of academic interest to most users, but is helpful if the user wants an instant indication of the sample rate of the currently playing audio format.  These are the colors currently implemented:
  • 44.1kHz    -  Dark Blue
  • 48kHz       -  Red
  • 88.2kHz    -  Lilac
  • 96kHz       -  Pink
  • 176.4kHz  -  Turquoise
  • 192kHz     -  Orange
  • 352.8kHz  -  Purple
  • 384kHz     -  Yellow
  • DSD64      -  Dark Green
  • DSD128    -  Light Green
  • DSD256    -  Pale Green
If any other sample rates are played the color will remain black.


BitPerfect comes with a few options you can use to find the perfect sound with your system.

  Because BitPerfect is designed primarily to be a cutting edge audiophile music player, some of these options allow you to make compromise choices between the best sound quality, and the overall effectiveness of the integration with iTunes.  For many users, these options will deliver subtle improvements in sound quality that may not be resolved by their equipment.

These set-up options are accessed from BitPerfect’s Preferences Window.  BitPerfect’s Preferences Window has five tabs labelled General, Sound, iTunes, DSD, and Advanced.  The various settings available under those tabs are described below.

Audio Output Device

This is the device which will be used by BitPerfect to play your music, and this is one of two places where you can make that selection.  Any selection you make here is independent of any selection you might make in OS X’s System Preferences or Audio Midi Setup.  In fact, it will over-ride any selections that you may previously have made there.  When BitPerfect is using its selected Audio Output Device it puts it in “hog” mode, sometimes also known as “exclusive” mode.  This means that no other App - including OS X - can access it.  You can easily tell when BitPerfect is “hogging” the Audio Output Device, because its Menu Bar Icon will change from black to some other colour, depending on the audio format being played.

The audio output device can also be selected directly from the Audio Output Device setting in the Menu Bar drop-down menu.

Integer Mode

Integer Mode on the Mac platform is considered by many audiophiles to be the most sonically accurate playback mode.  Integer Mode was originally only available under OS X 10.6 ("Snow Leopard"), for supported DACs.  Starting with OS/X 10.7 ("Lion"), and continuing with OS X 10.8 ("Mountain Lion"), Apple discontinued support for Integer Mode.  However, starting with OS X 10.9 ("Mavericks") support for Integer Mode has once again been re-introduced.

If your combination of OS X and DAC supports Integer Mode, the 'Device Capability' section in the General tab of BitPerfect's Preferences Window will display a check box where you can choose to enable Integer Mode.  

If either OS X or your DAC does not support Integer Mode, the check box will not appear.

Recommendation:  Enabled.  Integer Mode, if available generally improves sound quality.

Troubleshooting:  If your system supports Integer Mode and you are getting static instead of music, or persistent clicks, disable Integer Mode.  Please contact BitPerfect support and include the output of the "Device Info" screen.  Some DACs actually have poor support for Integer Mode and cannot be reliably used in that mode.

Memory Buffer (MB)


This refers to the Audio Buffer.  The Audio Buffer size controls how much system RAM BitPerfect should set aside to store decoded and processed music for memory playback.  The default value of 256MB is sufficient for most CD quality music.  If you listen to high-resolution music or long classical tracks you may want to increase the buffer size.  Generally you should not increase it beyond one quarter of the total amount of RAM in the system.  Also, please note that the Audio Buffer is not the same thing as the Device Buffer mentioned later.

Recommendation:  If your system has 4GB of RAM, use 256MB or 512MB, otherwise with 8GB or more of RAM, use 512MB or 1024MB.  Our experience shows that there is little to no sonic benefit to be gained by allocating more than 512MB to 1024MB to the audio buffer.  RAM allocated to the Audio Buffer is no longer available to the Operating System, so it is important not to allocate more than you really need.

Troubleshooting:  Make sure Buffer Size is not more than one quarter of your total RAM.  If you know other applications are using lots of RAM, you may need to decrease this further.  Sound quality is not significantly affected by this option, so if in doubt it is safe to err on the side of a lower number.  Always bear in mind that the sound quality of BitPerfect will be at its best if your computer is doing as little as possible other than playing music.


SRC is an acronym, standing for Sample Rate Conversion.  A sample rate converter is an algorithm that changes the sampling rate of your music.  Many audiophiles believe upsampling can improve sound quality.  This option controls which algorithm will be used for both upsampling and downsampling.  In our opinion, any of the three SoX options are a better choice than Core Audio.

BitPerfect will automatically downsample any tracks that cannot be played at their native sample rate if your selected output device will not support it.

Recommendation:  SoX VHQ MinimumMinimum Phase filters are becoming very popular among discriminating audiophiles, but frankly, each of the choices has their adherents.  If you are unsure, try the various options and see which one you prefer.

Troubleshooting:  N/A, there are no known cases where the choice of sample rate converter can cause a problem.


Upsampling controls whether BitPerfect will increase the sample rate of the music you're playing to the value you choose.  If the option to "Upsample by powers of two" is selected, BitPerfect will only double, quadruple, etc ... the sample rate.
For example, if Upsampling is set to
Maximum Supported" and your DAC will support 192kHz, BitPerfect will upsample all tracks to 192kHz.  If you check "Upsample by powers of two", BitPerfect will upsample all CD quality files (CD sample rate is 44.1kHz) to the highest power of two supported by your DAC, such as 176.4kHz (i.e. 44.1kHz x 4).  There is an option to disable upsampling on a per-track basis (see below).

If you set Upsampling to a fixed sample rate, and check "Upsample by powers of two", then in the event of a conflict, upsampling by powers of two will take precedence.  For example, if you set Upsampling to 96kHz and check "Upsample by powers of two", and play a 44.1kHz track, BitPerfect will upsample it to 88.2kHz rather than 96kHz.  If you uncheck "Upsample by powers of two" it will instead upsample it to 96kHz.

Recommendation:  This is a matter of taste.  The sample rate converter will generally perform better when upsampling by powers of two, but many DACs will automatically upsample the incoming signal internally by design.  The best option is to try the different converters and upsampling rates and decide what you like best.  It may boil down to whether you prefer BitPerfect's upsampling algorithm to your DAC’s.

Troubleshooting: If you have an optical DAC which you plug into a USB to optical converter, be aware that the converter may support sample rates higher than the DAC itself will support, and that BitPerfect has no way of knowing this.


If you use BitPerfect to perform volume control or sample rate conversion, this work is done in our 4th-Generation 64-bit audio engine to ensure maximum quality.  Digital audio data, whether 16-bit or 24-bit, acquires additional bits of data precision as a result of this processing, after which the original 16 or 24 bit structure needs to be recreated.  Dithering is an optimized mathematical process for accomplishing this, which many listeners find improves the sound.  Many listeners are agreed that dithering is essentially inaudible with 24-bit audio data.

Recommendation:  This is again a matter of taste, but Triangular High Pass Dither should give best results.

Troubleshooting:  N/A, there are no known cases where dither can cause a problem.

Maximum Sample Rate

If you are using an optical DAC connected via Toslink to your Mac's optical output, your Audio Output Device should be set to Built-In Output.  It is important to note that the Built-In Output may support higher samples rate than the DAC itself.  However, the Built-In Output will only report to BitPerfect the sample rates it supports, rather than those supported by the connected DAC.  If this is case in your system, be sure to set this option to the maximum sample rate supported by your DAC, rather than the maximum supported by the Built-In Output itself.

The same considerations will apply if you are using an external USB-to-Optical converter instead of the Built-In Output.

Recommendation:  Unless the above applies to you, set this to "Maximum Supported".

Troubleshooting:  N/A unless you are using an optical connection.

Maximum Bit Depth

If you are using an optical DAC connected via Toslink to your Mac's optical output, your Audio Output Device should be set to Built-In Output.  It is important to note that the Built-In Output may support different bit depths than the DAC itself.  However, the Built-In Output will only report to BitPerfect the bit depths it supports, rather than those supported by the connected DAC.  If this is case in your system, be sure to set this option to the maximum bit depth supported by your DAC, rather than the maximum supported by the Built-In Output itself.

The same considerations will apply if you are using an external USB-to-Optical converter instead of the Built-In Output.

Recommendation:  Unless the above applies to you, set this to "Automatic (Optimal)". "Maximum" may be a better choice if you often use the iTunes (software) volume slider.

Troubleshooting:  N/A unless you are using an optical connection.

Use Maximum Device Buffer Size

The Device Buffer is NOT the same thing as the Audio Buffer mentioned previously, whose size is set by the “Memory Buffer (MB)” setting.  The Device Buffer is the output buffer allocated by the output device driver for data being sent to the audio output device.  Although you might be forgiven for imagining otherwise, it is NOT normally a good idea to set this to its maximum size.  When selected, this will configure BitPerfect to send as much data to the DAC as possible all the time. The idea is that this reduces CPU use in BitPerfect and can improve sound quality.  However, in practice, it often causes more problems than it solves, particularly under Integer Mode.  It is provided here primarily as a diagnostic tool to be used under the direction of BitPerfect Support.
  90% of all problems reported to BitPerfect Support are caused by users enabling this setting.

Recommendation:  Disabled.

Troubleshooting:  This setting is very much DAC-dependent.  If you have problems with clicks, particularly in Integer Mode, then you can try checking this setting.  However, you would be better off contacting BitPerfect Support for guidance.

Default to Inverted Polarity

Some audiophiles, and some systems, are able to detect and reveal subtle sonic differences when the music is played with reversed polarity.  This effect is normally very difficult to detect.  Many audio components (such as amplifiers) reverse the polarity as the signal passes through them.  This setting enables the polarity of every track to be automatically reversed, thereby compensating for such behaviour in the downstream electronics.  BitPerfect can also do this on a per-track basis (see below).

Recommendation:  Disabled.

Troubleshooting:  N/A, there are no known cases where Inverted Polarity can cause a problem.

Disable Gapless Playback

BitPerfect manages Gapless Playback in the theoretically best possible way - while one track is playing, the next track is pre-loaded into a second memory buffer.  This way, switching between tracks is instantaneous, since playback is simply switched between two memory buffers.  This method relies upon BitPerfect receiving accurate information from iTunes, identifying which is the next track to be cued up.  For reasons described in more detail here, iTunes sometimes provides BitPerfect with the wrong information.  This can result in glitches, or fragments of the wrong track being played, as BitPerfect detects - and then corrects for - the error.  If the music you listen to does not require true Gapless Playback (i.e. if there is a distinct break in the music between tracks), you can check the Disable Gapless Playback checkbox, and BitPerfect will no longer attempt to pre-load the next track into memory.

Additionally, there is a known problem when using iTunes “Shuffle” mode.  iTunes always reports to BitPerfect that “Shuffle” mode is off, regardless of the actual setting, and this can cause BitPerfect to queue the wrong track for gapless playback.  We recommend checking “Disable Gapless Playback” whenever iTunes is in “Shuffle” mode.

Recommendation: Leave it unchecked unless you encounter the problems described above.

Troubleshooting:  N/A, there are no known problems associated with this option.

Start iTunes on Startup

This option automatically launches iTunes whenever BitPerfect is launched.

Recommendation:  Enabled.

Troubleshooting:  N/A.

Minimize iTunes Interaction

This option reduces CPU use in BitPerfect and iTunes by reducing iTunes activity.  For users concerned about minimizing hard disk activity during playback, enable this option.  This option also has the effect of stopping iTunes from running muted in the background (see “Stop iTunes using AirPlay Devices” below), and means that BitPerfect now takes control over the position of the iTunes track progress bar, which, as a consequence, is only updated once per second.

After toggling this setting, it is necessary to Disable Bitperfect and re-Enable it using the commands in the menu bar drop-down menu, or Quit/Restart BitPerfect.

Recommendation:  Enabled.  Minimizing iTunes interaction can subtly improve sound quality.

Troubleshooting:  If you are experiencing problems with tracks repeating parts, not advancing correctly, suddenly stopping or starting, disable this option.  Please report any such issues to BitPerfect support so we can fix these problems and improve this option over time.

iTunes Response Speed

Controls how often BitPerfect checks iTunes' status.  This determines how quickly or slowly BitPerfect responds to changes like pausing a track or dragging the volume control slider.  Faster response speed increases CPU use, and may have an adverse affect on sound quality.

  This option is disabled when "Minimize iTunes Interaction" is enabled.

Recommendation:  The default setting of 1-tick left from "Fast".

Troubleshooting:  If you are experiencing problems with tracks repeating certain parts in a loop, move this option towards "Slow", or enable "Minimize iTunes Interaction".

Default to Fixed Indexing

BitPerfect relies on iTunes telling it what track is due to play next, so that it can manage gapless playback.  Unfortunately, sometimes iTunes provides incorrect information to BitPerfect, and when it is time to start the next track BitPerfect suddenly finds it has the wrong track queued up and playing.  This causes stuttering at worst, and gaps in gapless playback at best.  Checking “Default to Fixed Indexing” relies on an undocumented feature of iTunes, and can on occasions be a useful fix for this problem.  Additionally, try playing the album from within a playlist, and not from within iTunes’ music library.  Sometimes deleting and re-importing the album can work (particularly re-importing the album one track at a time, in track order).

“Default to Fixed Indexing” works on your whole music library.  Alternatively, you can use the ‘fixedindexing’ iTunes comment field (see below) on individual tracks within an album.

Recommendation: At the time of writing (with iTunes 12.5.5 and OS X 10.12.3) BitPerfect’s Reference System obtains the best performance with it checked.

Troubleshooting:  N/A, there are no known problems associated with this option.

Stop iTunes using AirPlay Devices

BitPerfect can only play the audio output through an “exposed” device, i.e. one that is listed in Audio Midi.  In OS X 10.7 ("Lion") and earlier versions, AirPlay was proprietary to Apple, and was not made available as an exposed device – BitPerfect and other third party Apps could not use it.  With the release of OS X 10.8 ("Mountain Lion") this changed, and AirPlay is now an exposed device, and BitPerfect can access it.

When BitPerfect is playing a track, iTunes is also playing the track in the background.  The iTunes playback is directed to an unused output device, but the sound is muted.  Which unused output device is selected is determined by OS X, and depends on how you have set up your system.  If OS X selects the AirPlay device, this can have some unintended consequences, such as turning on, or unexpectedly muting, an Apple TV for example.  At the time of writing, we are still hearing from BitPerfect customers who are encountering these issues, so we have not yet identified and resolved all of the outstanding issues.

If you check “Stop iTunes using AirPlay devices”, BitPerfect will attach itself in the background to the AirPlay device in such a way that no other Apps can use it, thereby preventing some of these issues.

Using OS X 10.12 (Sierra), the AirPlay subsystem has changed dramatically, and this setting no longer functions reliably.

Recommendation:  Disabled.  Please contact BitPerfect Support and provide us with a detailed description of the problem you are encountering if you find you need to enable this.

Troubleshooting:  N/A, there are no known specific problems associated with this option.

Enable Sound Check

Starting with v3.0.1 BitPerfect can can read iTunes' Sound Check values.  If this option is enabled, BitPerfect will apply a volume adjust to each track as determined by its Sound Check value.  This will be done in BitPerfect's 64-bit Audio Engine.  Sound Check is designed to equalize the perceived loudness of all the tracks in your music library so that they all appear to be playing at the same volume.  This effect may not be suitable or desirable for all types of listening.

BitPerfect only reads your music library's Sound Check values when it launches.  If you add music to your library after BitPerfect has launched you will have to quit and re-launch BitPerfect in order for the new tracks' Sound Check values to be registered.

Enable DSD

Please take particular care to read the separate section on DSD Support before you consider enabling this functionality.

I/O Procedure Duration

This option operates at the fundamental levels of BitPerfect's sound engine and its interaction with the computer's operating system.  Moving the slider to the left left can provide improved sound quality in high-resolution audio systems, but could also cause "Overload!" messages in the Console Log, sound corruption, and other unexplained problems.  These are areas in which perhaps the greatest optimizations in sound quality can be realized using BitPerfect, but will require great patience and determination on the part of the user.  Users experimenting with this slider should be taking great care to ensure that the computer is used only for audio playback in order to achieve the intended benefit.

Recommendation: Start with the slider all the way to the right.  Try gradually moving the slider left and see if you notice an improvement, without encountering unexplained problems.  Each time you move the slider, you have to re-start playback to initiate the change.  If this level of tweaking leaves you feeling uncomfortable, leave the slider at its right-most position and ignore it!

Troubleshooting: Before trying any other troubleshooting measures, make sure to move this slider all the way to the right, the default position.

Use BitPerfect 2.x iTunes Communication

This option is included purely for diagnostic purposes.  It over-rides a setting that BitPerfect chooses upon launch based on which version of OS X you are running.  It should never require user intervention.

Recommendation: Don't touch it!  Seriously ... don't touch it!

Troubleshooting: Contact BitPerfect Support before you consider making changes to this setting.

iTunes Comments

BitPerfect can interpret text in the iTunes Comments field to play a particular track in a different way. BitPerfect supports the invertpolarity, monophonic, donotupsample, volume,  fixedindexing, and invertchannels comments in the track’s iTunes Comments field.  All comments are case insensitive, and can appear anywhere within the comments field:

Add invertpolarity to invert the polarity of the track.

Add monophonic to play the track in mono.

Add donotupsample to disable upsampling for a particular track.

Add volume:[adjustment]dB to boost or attenuate volume for a particular track.  Specifying a negative number attenuates volume, a positive number boosts volume.  The number must end in ‘dB’ (case insensitive).  For example, volume:-5.5dB will lower the volume by 5.5dB for this track.  Be very careful using this feature to increase the volume, as system damage may occur.  Adjustments specified here will over-ride any Sound Check settings.

Add fixedindexing to change the playlist indexing system.

Add invertchannels to swap the left and right channels of the track.

DSD Support

Starting with version 2.0, BitPerfect offers the possibility to play DSD files natively.  Compared to the standard PCM form used by all computer audio, DSD is a totally different format for encoding music digitally, but many audiophiles are convinced that it is sonically superior.  Regardless, one advantage is that the majority of recordings released in DSD format are either recorded under exceptionally high quality conditions, or are remastered with the utmost attention to sound quality.  For this reason BitPerfect is an enthusiastic supporter of DSD!

In order to play files encoded in DSD it is necessary to have a DAC which supports DSD playback.  At the time of writing, relatively few DACs have this capability, but the large majority of specialist DAC manufacturers are announcing DSD-compliant products under development.  In the Mac environment there is an additional limitation due to the fact that OS X itself does not support native DSD playback.  In response to this situation, the industry has developed a technology called “DoP” (DSD over PCM) which is a way of dressing up a DSD data stream to look like a normal PCM data stream for transmission to the DAC.  At the input of a DSD-compliant DAC this DoP data stream is recognized and the content is played as DSD.  A non-compliant DAC would see it as an ordinary PCM data stream and play it normally - but the result would be noise.

There is one major drawback with the DoP system, and that is that there is currently no way for OS X (or for playback software such as BitPerfect) to be able to detect automatically whether an audio output device supports DoP.  It is therefore incumbent upon the user to provide this information.  Of course, this also means that there is little to prevent a user from declaring an audio output device to be DSD-compliant when in fact it is not.  The consequences of playing DSD on a Mac through an audio device which does not actually support DSD can be loud hiss.  The DoP specification does a good job of minimizing the loudness of this hiss, but in a worst-case scenario it can conceivably cause equipment damage, or damage the hearing of a listener using headphones.  This is entirely due to the limitations of DoP as currently constituted, and applies equally to any other playback software that utilises it.  Under no circumstances will BitPerfect be held liable for any such consequences.

Enable DSD

This tab contains a checkbox which enables all DSD support within BitPerfect.  If you cannot make use of DSD support, it is important that you leave this checkbox permanently unchecked.  In order to make use of DSD support within BitPerfect  ALL of the following must apply:
  1. You have a DSD-capable DAC.  You must be certain that your DAC supports DoP, and fully understand its capabilities.
  2. You have one or more DSD audio files in DFF or DSF format.  You must be prepared to convert those files into “Hybrid-DSD” format.
  3. You must have purchased “DSD Master” from the Mac App Store.  DSD Master is used to create “Hybrid-DSD” files.
  4. You have read, and fully understood, this User Manual.
If all of those conditions are met, then you can proceed to enable BitPerfect’s DSD support.  However, all users who enable DSD playback under BitPerfect remain responsible for ensuring that all devices and settings are configured correctly.

Each time you select a new audio output device, BitPerfect will inspect its capabilities.  If those capabilities meet certain minimum requirements which are needed for DoP playback, then, if DSD Support is enabled, BitPerfect will ask you whether this device supports DSD.  It is the user’s responsibility to know whether or not the device supports DSD, and to check the correct option.  However, anything you select here can be overridden later in the DSD Device Window which appears in the DSD tab in BitPerfect’s Preferences window.

DSD Device Window

If you have enabled DSD support, the DSD tab in BitPerfect’s Preferences window will display the DSD Device Window.  This lists all of the available audio output devices, and lists their DSD capabilities.  There are many different variants of DSD, but the most important is usually known as DSD64*; others include DSD128* and DSD256*.  BitPerfect supports only these three DSD formats.  Almost all commercially available DSD is in the DSD64 format (in fact the term “DSD” only properly refers to DSD64 - the term has been hijacked for convenience), but some recordings are being made available by specialist studios in DSD128 and DSD256 formats (as well as in other variants not presently supported by this release of BitPerfect).  The DSD Device Window enables you to fine tune which of these variants of DSD are supported by your DAC.  Note that BitPerfect will automatically grey out some of these selections if it has detected that the PCM playback modes required to support them are themselves not supported.

*DSD64 refers to DSD with a sample rate of 64x 44.1kHz (2.8224MHz).

*DSD128 refers to DSD with a sample rate of 128x 44.1kHz (5.6448MHz).
*DSD256 refers to DSD with a sample rate of 256x 44.1kHz (11.2896MHz).

Additionally, BitPerfect supports a legacy DoP format used by some older DACs, such as certain models produced by the company dCS.  This setting is labelled dCS DoP.  Do not enable this setting.  We strongly recommend you contact BitPerfect Support before you consider using this setting.

Hybrid-DSD files

A Hybrid-DSD file is a special file type created by the App DSD Master, available on the Mac App Store.  These files are normal Apple Lossless files, and contain a PCM version of the DSD original.  Because they are normal Apple Lossless files they can be imported into iTunes, and will play normally whether or not BitPerfect is present.  However, they also contain the original native DSD data hidden inside them.  BitPerfect 2.0+ is capable of reading and playing the native DSD content.  If DSD support is enabled, and if the selected audio output device supports DSD, then BitPerfect will automatically play the native DSD content.  Otherwise it will play the PCM content.  If any software other than BitPerfect is used to play these files, it will play the PCM content.  All this happens automatically, with no further user intervention required.  We believe this is the most friendly imaginable way of supporting DSD playback.  You can read more about DSD Master on its own Blog Page.