24-bit Pandora?


#1

I have a Squeezebox Touch hooked up to my DS with a Shunyata Anaconda SPDIF digital cable. I stream Pandora, Spotify and Tidal. I was wondering if anyone could explain why the DS screen shows Pandora’s feed as 24/44.1 and Spotify and Tidal feeds as 16/44.1? Clearly, the Squeezebox Touch is up converting the 256k feed from Pandora, but why is Pandora’s feed 24 bit and Spotify and Tidals feeds merely 16 bit?? Actually, I heard one classical album on Tidal that read 24 bit. I am running the Squeezebox Touch and DS volumes both at 100. I actually prefer the sound of some music on Pandora over what I hear on Spotify and wonder whether this 24 bit up conversion might have something to do with it. Just curious.

Vance


#2

That’s an interesting question.

Don’t use Pandora myself, but I have noticed that when playing any of the AAC-encoded iTunes files via my SqueezeBox I get 24-bit instead of the 16-bit output from lossless CD rips. Also iTunes Radio via optical from Apple TV comes through as 24-bit.

My guess so far has been that the AAC encoding process tries to describe the audio as a mathematical function. When you decode it back to PCM it’s like plotting the function on graph paper, which you can do to any degree of precision you like. (X-axis resolution is related to sample rate, Y-axis to bit depth.) Plotting it to 24-bit wouldn’t be making anything up, it’s just more precisely representing the function provided by the AAC file.

Your experience makes me wonder whether I could be off track though. Why would you get 16 bit on some tracks and 24 on others? Do we know whether those services use the same codec for all tracks? Possibly the SBT decodes one format to 16 bit and another format (eg AAC) to 24 bit.


#3

Dvorak,

That was very helpful. So far, the one classical album on Tidal has been the only 24-bit one I have noticed. I think your theory sounds very plausible. How do you perceive the sound quality of AAC encoded files? I guess my question is whether this 24 bit read results in enhanced SQ. Probably not, I assume.