Yes, it does matter.

You are correct that the UltraPlusPak has compressed files.

When BIAB creates a backing, it converts the compressed files to wav/aiff and then pieces the backing together. Because the original compression from wav to m4a slightly reduced the sound quality, the re-created wav/aiff file(s) lacks a little quality when compared to the original files. For the most part, this quality difference is not all that noticeable. However, when a backing is created and then compressed, the compressing will reduce the quality slightly more again because the Realtracks undergo a second compressing.

In my experience, it's best to leave the backing as an uncompressed file for as long as possible for mixing purposes. This will help maximise sound fidelity.


MY SONGS...
Audiophile BIAB 2025