HD550 users have the ability to plug in an XLR or ¼” audio input directly into their unit without the need for a USB adapter.
Please note that these inputs support mic level audio signals only. If your audio equipment is line level, see here for a workaround.
When you plug in your audio source, be sure to add it as an audio input by going to Settings: Audio In, and click the + button.
When you click Save, you will see the source in the audio mixer. You may notice a very low level of sound coming in.
This low level of audio may appear regardless if your source is connected or not.
This white noise should not exceed -48dB on either input. It is characteristic of all USB-based PC audio devices and is virtually inaudible.