is the S/PDIF output of a Hifiberry Digi+ attached to a Raspi2 independent of the input format to VOLUMIO stored on USB-device or NAS - WAV or FLAC?
With other words: is the S/PDIF output of the Hifiberry Digi+ readable for every device with S/PDIF input, no matter if the data originally were stored in FLAC, WAV - both with identical output - or even MP3 format, the latter for sure not being identical?
I am nearly sure that the answer must be YES, but before I start to rip to FLAC…!
So S/PDIF uses a format of its own, this format capable of transporting low-res (MP3), normal-res (WAV, FLAC) and hi-res (WAV, FLAC, maybe SACD - each in higher resolutions).
As FLAC is lossless, theoretically S/PDIF should output (via HiFiBerry Digi +) bit-identical information as from WAV files.
Does anybody know if the process of regaining full information from FLAC input disturbs Raspi`s capabilities, Patrick used the word “resample”, this made me think of that possible issue . . . ?
S/PDIF is a signal transport format, not to be confused with a music file/compression format, capable of transporting audio signals beween devices. It has some limitations in the maximum bit depth (20 to 24 depending on the devices) and bitrate/samplerate (up to 192khz when using COAXial connections. Most TOSLINK connection have a lower limit) it can transport.
As I said you would ideally have the music files and the transport bit depth and samplerate the same because than there is no need to re-sample the audio signal (meaning either generating bits somehow or leaving out bits) leaving the signal as original as it can be.
The more conversion there are done between the original record (DSD or DXD nowadays), the file format you use to re-create the audio signals and the transport formats, the more ‘noise’ there will be in the end result.
My advice: look for quality recordings and get, directly from the recordings, the highest quality file format you can play without having to re-sample for transport.
An original 24/96 or 16/48 FLAC often sounds better that an up-sampled 24/192 or 24/384 MP3