24vs16bit What happens when...?

[espasonico]

What happens to the bits when you create a 16bit Protools session but you use a 24 bit converter ? What happens with the headrom ? Do I need to record at higher levels ?

Thanks

[Jules]

Many 24 bit converters have a built in option somewhere to work at 16bit.

If you don't want to record at 24bit for some reason (?), investigate how to set your converter to operate at 16 bit.

I have always understood that it is bad voodoo to send 24 bit signal into a 16 bit session, but I will let someone more learned explain or debunk this.

[kafka]

Originally Posted by espasonico

What happens to the bits when you create a 16bit Protools session but you use a 24 bit converter ? What happens with the headrom ? Do I need to record at higher levels ?

16 bits full scale equals 24 bits full scale, in terms of dBu. You're just expressing it with a number with fewer significant digits. The 8 bits lost are the least significant 8 bits.

[espasonico]

Well, I´m asking this just for curiosity. I get sessions from another studio where they record at 48kHz and 16bit ( kind of concert film thing ) and I have to make some overdubs on those sessions and send them back ( they want to work at 16bit for whatever reason ). I know I could open a 24bit session, convert original files to 24 bit and then just give them my overdub files dithered to 16 bit and import them again in the original session but is crazy stuff and it would take forever ( 2 hour concert )

For example, my Rosetta 200 has the option of 16bit using the UV22HR but I don´t know what happens if I´m using a Digi 192 and a 16bit session or any other converter without the dither option. Does the dithered mixer dither the recorded input ?

Also I´m thinking about if I would need to record hotter than when I do when tracking at 24bit, because that would mean to record nearly -0dbfs peak wich I´m not used to ( watch the meters praying for no clipping )

[kafka]

No, you don't need to adjust your levels differently. Just set them the way you normally do. Don't worry about the converter. If the session is 16-bit, it will handle the data from the converter appropriately. Do not convert back and forth between 16-bit and 24-bit. If they send you 16-bit, just work in that. That is the safest way.