To reply to the original poster's question, I think the difficulty comes from confusion between 24-bit vs. floating-point
storage and 24-bit vs floating-point
processing. They are separate and independent from one another.
Storage: Pro Tools 10 can store recorded audio in either 24-bit or floating point
files. Floating-point files provide an improvement only when storing a
processed signal, such as with AudioSuite processing or mixing down tracks. They do not help with signals recorded from an audio interface. See
this post for more details.
Processing: Mixing and plug-in processing are independent from the storage format you're using. Native and HDX systems use floating-point processing; HD uses fixed-point processing. You can produce great mixes with both of them. The main difference you will notice between the two is:
- Floating-point processing will not clip internally (such as when mixing between two busses), only at the output stage when going back to your interface (or when bouncing to a fixed-point file)
- With floating point processing, you don't have to worry about gain stages that bring a signal down really quiet. With fixed-point, you would lose signal quality if you bring the signal down far at one point, then back up later.
Also, the HDX and Native mixers use 64-bit accumulation for mixing, which will retain greater precision. Some people say they can hear the difference between this and 48-bit fixed point accumulation.
So the main difference with floating point processing is that your session's mix is much more forgiving about the gain staging, and won't clip or lose precision during routing between busses, sends, and submixes.
I hope that helps.