The PC-USB connection on your Rotel device has two USB settings. The default setting is USB Class 1.0, which supports audio up to 96kHz. In order to support 192kHz audio, your Rotel device must be set to USB Audio Class 2.0 in the setup menu, and if you are using a Windows PC you must also make sure the USB 2.0 drivers are installed. Also, you may need to adjust the sample rate output on your computer as well.

For Windows PC users, you can find the USB 2.0 drivers on the CD included with your Rotel product, or you can download the drivers here.

Changing the Rotel device to USB Class 2.0

For models with a front display, to change the USB class to 2.0, press the MENU button repeatedly until you reach the menu PC-USB AUDIO CLASS, then change this setting to 'USB 2.0'.

For the RDD-1580 DAC, follow the steps below to change the USB Audio Class:

1. Press and Hold the PC-USB source button on the front panel for 5 seconds. The current USB audio mode is indicated by the blinking Sample Rate LED as: 
   • USB Audio Class 1.0 – Sample Rate 96kHz blinking (Factory Default)
   • USB Audio Class 2.0 – Sample Rate 192kHz blinking
2. Press the PC-USB key again to illuminate the 192kHz sample rate light blinks.
3. Pressing the PC-USB key will toggle between USB Audio Class 1.0 (96kHz light blinks) and USB Audio Class 2.0 (192kHz light blinks).
4. After the desired USB Audio mode is selected wait 3 seconds for the selection period to end and the RDD-1580 will use the selected audio mode.
5. Power cycle the RDD-1580 and reboot your PC after changing the USB Audio mode to ensure both units are properly configured.

Adjusting the Sample Rate on the Computer

If your Rotel device has already been set to USB 2.0 (and the driver has been installed if you are using a Windows PC), the next step would be to check/adjust the sample rate settings on your computer.

• Mac OS X Users - Select Applications->Utilities->Audio MIDI Setup, then highlight the Rotel audio device from the list on the left side of the Audio Devices window. Choose "Use this device for sound output" if this has not already been selected. From this menu you can also select the desired Sample Rate to use, so if you are going to be listening to high-resolution audio files select the appropriate sample rate setting from the Format menu here as well.
  
  
• Windows Users - Select Start->Control Panel->Sound and Audio devices->Playback, then select the Rotel audio device from the list and select 'Properties'. Click the 'Advanced' tab and choose the desired sample rate from the Default Format tab.

An important note about changing the output format - since most of the recordings you will play from iTunes will have been ripped from 44.1kHz CDs, you will want to play them back at their native rate, so the computer needs to be set up to output 44.1kHz. If you leave it set at a higher resolution (96kHz, 192kHz etc), the computer will convert the audio up to this higher resolution which can reduce the sound quality, so it is important to only adjust the sample rate when you intend to play higher resolution audio files.

Software packages like Pure Music and Amarra are available for Mac users to help manage things like automatically playing back music files using their native rate. This eliminates the need to manually make changes if you frequently switch between 44.1kHz and 96kHz or 192kHz recordings.