If you own an HD550 and wish to use a line in audio input rather than a mic in audio input, you will need to add an additional accessory to your setup.
The HD550 XLR inputs support mic level inputs only, which ranges from -60dBV to -40dBV. Line level audio on consumer products starts much higher at -10dBV.
If you add a Whirlwind IMPAD In-Line XLR Barrel Transformer to your workflow, this will allow you to bring in a line level source into the XLR inputs on the HD550. These accessories reduce the decibel (dB) level coming from your audio source so that Studio can support it.
These barrel transformers vary based on the amount of dB they remove from the source. For example, the Whirlwind IMPAD40 removes 40dB from your source's audio. Also available are:
Simply connect your audio source to the female end of the transformer, then connect the male end of the transformer to your HD550. Then configure your audio as you normally would.
We cannot guarantee that other similar products will work with the HD550 as we have not tested them. If you have success bringing in a line-in source using a different workflow, please let us know!