even if its the same resolution, its still the same story. just uncheck custom resolution or rebuild the video capture device from scratch and leave things default.I'm having the same issues here with the HD60 Pro. Have tried the standard 32bit and 64bit versions of OBS as well as multiplatform and the issue is constant across them all. I have also made sure custom resolution is unchecked and audio output for source for set to output to stream only.
Something maybe to note - whilst previewing stream, I can click "Configure" in my source properties to bring up the Elgato config panel and change options there from 720p 30fps to 1080/60 and immediately upon doing that, the stutter is gone in preview but once I confirm changes and close property windows, changes revert and the stutter returns.