When my interface is set to be the default audio device @48K, none of my audio players will work. Only when it's set to 44.1K.
 
This means I cannot use the interface as the default audio source while using Sonar, which I prefer to do so that all things audio outside of Sonar go to the interface, not the computer speakers.
 
The only way I can use it as the default is to switch back and forth from 44.1K to whatever I'm using in Sonar or pipe the speakers to the interface which doesn't have enough inputs for that to work.

Where are you setting the default sample rate, Windows, the interface software or both? I would suggest setting it in both.

Interface is set to 48K (Options: 44.1, 48, 88.2, 96). No option for bit depth but converters are 24bit.
On board soundcard is set to 48K/24bit, which is why I don't understand why audio players don't like the interface set to the same level.
 
Not sure where else to go in Windows.
 
How does Sonar handle audio when it's set to 48K/24bit and the interface is set to 44.1K?
If Sonar overrides the interface setting I should be able to leave it at 44.1.

Keep in mind most programs do not use the ASIO driver. If you plan on using the external interface with SONAR and other applications, they will either need to run at the same sample rate or have exclusive control of the the device. Typically ASIO drivers work at a single bit depth but other drivers may have different settings. All window settings for the onboard and external interface at set in the Control Panel > Sound Playback and Record Properties. The Advanced tabs contains the sample rate and bit depth settings.

The "standard" (Red Book/CD Audio) wav file is 16 bit/44.1khz. 
 

scook
All window settings for the onboard and external interface at set in the Control Panel > Sound Playback and Record Properties. The Advanced tabs contains the sample rate and bit depth settings.

 
For the soundcard, the Advanced Tab is there for all audio levels (16/16000 thru 24/192000)
 
For the interface, the Advanced Tab only lists 2 quality settings (16/44100 & 24/44100).
It disappears when the interface is set to anything over that, so Windows is unable to see it then for some reason.
 
I don't think ASIO is an issue as the interface has both ASIO and WDM drivers. It's probably a limitation of the interface as it won't allow media players to operate regardless of whether Sonar is running or not. 

soens
For the interface, the Advanced Tab only lists 2 quality settings (16/44100 & 24/44100).
It disappears when the interface is set to anything over that, so Windows is unable to see it then for some reason.

That would seem to be the problem. Since Windows does not recognize settings higher than 44.1K, apps using the Windows settings will not be able to communicate to the interface if the interface is set higher than 44.1K. Seems strange to me the Windows driver does not support more options.

Especially since the drivers support 96K, but that's Behringer for ya! Sonar does override whatever you set the interface to so I'm stuck using the soundcard as default and piping it to a mixer input.
 
As stated tho, the audio players will work with the soundcard all the way up to 192K.

I wrote to Behringer about this.
They wrote back saying the UFX1204 only supports sampling @44.1K.
I wrote back asking why the manual states it supports sampling @44.1K, 48K, 88.2K & 96K, then.
Even the onboard recorder supports 48K with an external harddrive. 44.1K with flashdrive.
 
Waiting their kindly reply...

... still waiting.