Yep, generation loss kills quality (Destiny)

by RC , UK, Sunday, March 22, 2015, 11:24 (3782 days ago) @ Cody Miller

Or when you recompress them again, so you can play them on some other device. That's why having your CD as your master is the best.

The compressor can't tell the difference between the original signal and compression 'noise' because the data is gone. CD or a lossless format (like FLAC) are essential to have access to in order to preserve quality into the future. Or a service that keeps the lossless formats and re-encodes it to new formats/devices for you.

It really was a big problem in the MP3 player boom. Fortunately the format wars have settled down and modern devices have better format support (including Lossless forms) and bigger storage capacities.