I bought the following album as a CD on Bandcamp.
https://biosphere.bandcamp.com/album/inland-delta-2
As far as I can tell, the CD is a professional pressing
with the inside CD ring label handlewithcare.de.
I like to back up my CDs on the PC with EAC Secure
so that I can play them more easily and get a secure copy.
I created spectrograms with the program sox ("sox CD.flac -n spectrogram -o CD.png").
Now I compared the digital Bandcamp version
(which you kindly get with it) with the CD and was amazed to
realize that there is a clear difference in the upper
frequency range of every track.
As if there was some kind of filter on the CD.
I am not an audio expert, but I wanted to find out if anyone knows where the difference comes from?
Despite the fact that the difference on the Spectrograms is relatively clear, I can't hear any difference with a "mid-range headphone setup".
[Edit]
Bandcamp files are 24bit - 44.1kHz.
I noticed that the thread is probably better placed in https://hydrogenaud.io/index.php/board,1.0.html
I am not an audio expert, but I wanted to find out if anyone knows where the difference comes from?
It's probably shaped dither from the conversion to CD-compatible 16-bit/44.1kHz.
Despite the fact that the difference on the Spectrograms is relatively clear, I can't hear any difference with a "mid-range headphone setup".
If I'm reading your spectrograms correctly, the difference is mostly below -90dBFS and above 18 kHz. Most people wouldn't be able to hear that on any setup without turning the volume up to dangerous levels.
As said above it looks like shaped dither applied when converting from 24bit to 16bit.
This video explains what dithering does. Don't miss the conclusion at the end.
Digital Show & Tell ("Monty" Montgomery @ xiph.org)
https://youtu.be/UqiBJbREUgU?si=Cb3GFjJz4AuQYqlG&t=695