DSD Master introduces, for the first time, a new file format which we term "Hybrid-DSD". This is a file format which looks to the world exactly like an Apple Lossless (ALAC) PCM file, and functions exactly like one. "Hybrid-DSD" files can be loaded into iTunes, or into any other player which supports the Apple Lossless format, and will play music like normal. A "Hybrid-DSD" file contains a PCM copy of the DSD original. However, it also contains the original DSD data, encoded within the file in such a way that iTunes and other players won't attempt to read it. If BitPerfect is asked to play this file, it is able to read both the PCM and the DSD versions. If your DAC supports DSD, then BitPerfect will automatically play the DSD version, otherwise it will automatically play the PCM version. BitPerfect 2.0 and later is required to support this feature. All other playback software will only ever play the PCM version.
Why do we need a Hybrid-DSD file?
Good question! The main reason is to allow BitPerfect users to play DSD files. BitPerfect has for a long time now had the capability to play DSD, but since iTunes does not support DSD there is no way to load DSD files into iTunes. As is the case with FLAC files, if you cannot load it into iTunes, then there is no way to get BitPerfect to play it.
Other players have approached this problem with the use of proxy files. This is a file which typically looks like an Apple Lossless file, so it can be loaded into iTunes, but contains digital silence, of a duration corresponding to the duration of the DSD file. It also contains data telling the player the location of the original DSD file, which it can then load and play. These proxy files do work just fine, but they have some drawbacks which go against BitPerfect's sense of how an App should function.
The proxy file drawback that we dislike the most, is that if you try to play the file through a non DSD-compliant DAC, all you will hear is silence. This means that if you want to play your music through both DSD-compliant and non DSD-compliant DACs, you have to load both the DSD originals (using proxies) and the PCM versions as separate entities. Then you need to establish a method to identify which is which within iTunes, bearing in mind while doing so the capabilities of the DAC you have chosen to play through. At BitPerfect we believe that when you navigate through your music library, you should not be faced with multiple versions of your music, each labelled for a different purpose. You shouldn't have to remember what all these versions are and what they all do. You should not need to be an expert in the playback capabilities of each audio device that you might want to play your music through. We believe that the software should be able to do all that for you, with the minimum of driving skill required of the user. Hybrid-DSD files (and the 2.0 update of BitPerfect) have been developed with this purpose in mind.
Using DSD Master's Hybrid-DSD files, you can load into your player a single file which seamlessly switches between the DSD and PCM content according to the capabilities of your DAC and your player software. It has the further advantage that with DSD Master's proprietary PCM conversion algorithm, when listening to the PCM version you will enjoy the best possible PCM sound quality. All we ask of you is that you learn to operate iTunes. We think most audiophiles' cohabiting technophobes will have few - if any - problems with that.
How will I recognize my Hybrid-DSD files?
BitPerfect's new Hybrid-DSD files look like Apple Lossless files. In fact, strictly speaking, since they adhere fully to the Apple Lossless file specification, they ARE Apple Lossless files! For that reason, when DSD Master creates a Hybrid-DSD file it gives it a filename with ".DSDh" inserted between the original file name and the ".m4a" extension:
The ".DSDh" has no other function than to enable you to recognize Hybrid-DSD files at a glance, and differentiate them from regular Apple Lossless files. If you like, you can edit the file name to remove the ".DSDh", and this will have no impact whatsoever on its performance or behavior.
What about the PCM content?
When creating a Hybrid-DSD file, BitPerfect gives you the option of the full range of available sample rates for the PCM content, from 44.1kHz all the way up to 384kHz. You can choose whichever one you prefer, whether from the perspective of audio quality, DAC compatibility, or file size. Except for 44.1kHz which is dithered down to 16-bits, all formats maintain a 24-bit bit depth.
We recommend that the very best sound quality will be achieved using one of the 44.1kHz family of sample rates (44.1kHz, 88.2kHz, 176.4kHz, 352.8kHz). However, only the the very finest audio equipment will be able to resolve the audible differences between those sample rates and the 48kHz family (48kHz, 96kHz, 192kHz, 384kHz). [For the technically curious among you, this arises because the sample rate of DSD is precisely 64 times 44.1kHz, whereas it is an awkward 58.8 times 48kHz. 64 is an integer power of 2 - this allows the mathematics underlying the sample rate conversion algorithm to be slightly "cleaner".]
Your choice of PCM sample rate will involve a trade-off between sound quality and file size. Using Light Harmonic's amazing Da Vinci DAC (by a substantial margin the best we have ever heard), which can operate natively at up to 384kHz, it is our observation that incremental improvements in sound quality can be achieved, albeit with rapidly diminishing returns, all the way up to 352.8kHz. However, in the real world, your best choice for sample rate (based purely on sound quality) will normally be either 176.4kHz or 88.2kHz, depending on the quality and capabilities of your primary non DSD-compliant DAC. File size considerations may, however, be equally important factors in your particular situation.