The D1 is a USB Plug-and-Play audio device. which means that the drivers it uses are developed and provided by the developer of your computer's operating system. Because of this, you wouldn't need to download or upgrade any drivers to use your D1.
If for some reason you're having issues with your D1, the first thing we'd recommend is to use it with a different computer to see if the problem follows; this can help narrow down what the problem could be. If you're having issues with your D1 on a machine running Windows, one thing you can try is uninstalling the driver, removing the D1 from your computer, and plugging it back in to allow it to re-install. You can find instructions from Microsoft on how to reinstall a plug and play device like the D1 in the link below:
If you're on an Apple computer, you can do a NVRAM/PRAM reset. This resets the system configurations for some audio and video related things and can many times help clear up problems related to audio. See the link below from Apples support page for information on how to do this.