Originally Posted by Elader
a) what is the 'normal' bit depth and sampling frequency of internet streamed music? Does it matter if I listen through web browser or the spotify or mog app? For that matter, am I correct in assuming all my old crappy MP3s are sampled at 44K?
b)The DAC (musicstreamerII and MyDAC) 'knows' what settings to use based on the bitstream from the USB? I ask this because the MSII does have indicator lights. It stays glued on 96K when I set the computer output to 96K regardless of the source material.
c) Is the dac or the computer 'upsampling' - I suppose it would be nice to know. I am one of those guys who don't believe in creating something out of nothing - and would rather play music at the sampling rate it was recorded in.
d) Is it true that for the player to adjust its output based on the sampling rate and bit depth of the music file, you have to use another player that piggybacks on itunes? What happens if you dont? e.g. if I play a crappy MP3 through Itunes with the MIDI set at 96K/24bit? What does the mad do?
((a)) 44,100 samples per second at 16 bit depth. I've verified this for iTunes, MOG and Spotify.
((c)) The computer is upsampling in this case. I also prefer to avoid resampling: it can't make the sound better.
((d)) I abandoned iTunes as a player a year or so ago. I've heard rumors it can handle 24 bit audio now. I wouldn't rely on iTunes to play anything other than iTunes store material and mp3s. Apple simply has no incentive to do more.
I like to play my music without up/down conversion. I got tired of going into MIDI setup all the time so I bought Decibel. It's maybe $15. Decibel can completely bypass the OSX audio system (this is called "hog mode") and talk directly to the hardware. Decibel will automagically switch your DAC to the correct sampling rate and bit depth.
But if all your material is MP3s and stuff from the iTunes store, you can set MIDI to 44.1 and use iTunes as a player and you're pretty much golden. If you're system has a manual volume control (like on a headphone amp) then its a nice touch to set all the computer volume controls to 100%.
If your collection includes 90/24 material, I suggest buying a separate player (such as Decibel). There's some free ones too: Cog comes to mind.
An earlier poster makes a good point: DVDs are at 48000 samples per second. If you set the MIDI to 44.1., DVDs will be downsampled. If you set the MIDI to 48000, then your music will be upsampled. Adding DVDs to the mix, I'm not aware of a solution that will handling the sampling rate automatically. The whole mindset of the operating system people (Mac and Windows; Linux too if you consider PulseAudio) is that there are multiple, simultaneous sound sources, each potentially at a different sampling rate and bit depth. They're not thinking of matching the DACs rate to the music's sampling rate. The only way they can meet /their/ goals is to resample everything to a common rate (48000 or 96000, typically). They go to a lot of trouble to make sure everything gets resampled: resampling is a feature, a "good thing" from their point of view.
Much of the reason matching sampling rates to the DAC is hard is that we're fighting the design goals of the operating system.
Edited by nicko7i - 3/10/13 at 5:39pm