So I have an 18i20 from my side hobby that I tried setting up for working from home purposes due to COVID. What I had hoped to do was plug my work laptop dock (Dell wd19tb) into the audio in/out ports of the 18i20 to use my existing audio gear for phone and zoom meetings. The usb of the 18i20 is plugged into my personal computer and I was hoping to have both devices plugged in and mix audio with the Focusrite Control software.

However, when I plug the laptop in, I get some nasty audio feedback and haven’t been able to resolve the issue by plugging the devices into separate wall outlets, etc. Is this summed up as a use not intended for the 18i20 or are there any suggestions?

The laptop dock has a TRRS jack so I have a splitter plugged in and the cables plugged into the the audio in/out of the 18i20.