first of all, we need to understand what exactly you mean by „DTS passthrough“. We guess you are talking about the drop in quality of certain music files during HDMI playback on your Squeezebox server, e.g. FLAC files with 32 bit rate and 96 KHz sampling rate are played back with 16 bit and 48 KHz only.
If so, you should definitely try out the following steps to keep the original sound quality: Enter your Max2Play interface and go to „Raspberry Settings“. On the page, look for the section „Change HDMI Settings for Display Resolution, Framerate and Audio“ and activate „Enable High-Resolution Audio on HDMI“ by choosing „Max2Play Kernel with 192 Khz enabled“.
Please let us know what your results are.
Maximilian from Max2Play