Reasons for asking for a 32 bit float mix instead of 24

Bob Katz

Dear Mr. Bob Katz!

After owning several editions of your “Mastering Audio” and also your “Mastered for iTunes” this is the first time I’m reaching out to you personally. Because despite all my studies of your books there is one thing I don’t really know the precise explanation for. Maybe I’ve overlooked something, in this case I apologize for wasting your precious time.

What is the precise reason for asking for 32bit-fp audio when it comes to mastering? Is it rather the ability to reconstruct distorted audio, or is it because it avoids dithering at this stage? If for the latter, why than not even ask for 64bit-fp files? Simply because that would be overkill? 

Do you maybe have a link where this is explained in depth? And while I’m writing to you: do you maybe have a trusted source for the CD-text specs? Because as much as I searched so far, I could never find anything that really seemed to be fully reliable.

Thank you so much in advance and all the best,


Dear Sebastian.

The main reason to ask for 32 bit float is to protect from accidents or malpractice on the part of the mix engineer. If they go over full scale working ITB you can lower it later without penalty. With fixed point going over full scale would distort. 

Or if the level is very low, in floating point you can raise it with no theoretical or actual penalty. 

The other potential advantage is  mix engs might produce a 24 bit file without dithering. Is that advantage audible? Possibly not  but at least it’s technically correct. Basically in both cases you’re protecting yourself from accidental malpractice on the part of the mixing eng. 

From the point of view of signal to noise ratio if they had provided a properly dithered and leveled 24 bit fixed file, it would not lose any sonic advantages over 32 float. 24 bit dither noise is very very low. Hope this helps.