I've just noticed that SONAR is no longer allowing me to change the audio driver bit depth under Preferences>Audio>Driver Settings.  The box is grayed out and stuck on 24.  It's not a big problem for me, but I'd still like to know why it's doing that.  

Latest version of Platinum.  I'm using a MOTU 896mk3 interface with the most recent driver.

If you're using an ASIO Interface, try changing the bit depth in the ASIO control panel.

It's ASIO, but MOTU's control panel doesn't let me change the bit depth.  I can definitely remember being able to change it in SONAR before, I know I'm not crazy!  :)

For a few days I had the same problem.
It was up to an internal soundcard, so I could not change bit rate or bit depth in the asio control panel from a Roland Quad Capture. (this was a fresh installed computer). The internal soundcard locked the Roland Quad Capture.
Take a look if windows is using and "locking" your interface. That may be due to an windows update.

I have all of the Windows audio devices disabled under Control Panel>Sound.  Is there somewhere else I should look?  I don't understand how Windows would be taking control of the interface if it's disabled.

Preferences-->File-->Audio Data?

Out of curiosity, what kind of bit depth would you be interested in using for recording, other than 24?

rcklln
Preferences-->File-->Audio Data?

Works.

I wonder why I'm able to change it there, but not in the other place.

Sanderxpander
Out of curiosity, what kind of bit depth would you be interested in using for recording, other than 24?

16bit, but I generally do everything in 24.  I just want to know why I can't change the setting, because it could mean I did something stupid.

I just looked on my DAWs (we have 12 computers) and the bit depth is also locked to 24 Bit. I was wrong what I wrote in my post. I couldn't change the bit rate (44 - 96 - 192). But the bit depth was also 24 Bit.
All my audio-interfaces (12) are 24-bit-ONLY    (RME, Roland, Focusrite, M-Audio)
You can change the "record" bit depth to 16 bit under preferences -> audiodata.
Maybe this is what you want. But the interface is still in 24-Bit mode, even if it processes only a 16-bit signal.
 

It has always been in the Preferences-->File-->Audio Data, as far back as I can remember.
 
This question gets asked every couple of months or so.  I don't know why it is displayed and altered in two different places.  It kind of triggers the question in folks who are new to it, or who set it ages back and decide to alter it and forget that is in Audio Data that the edit to it takes place.
 
Bob Bone