Optical output only supports PCM so it won't transmit DTS directly.
Either:
- convert DTS to PCM in the software and send it that way to your receiver, or
- use HDMI is it's a possibility; it's by far the best option as it supports everything.

Hope this helps.
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M80 v3, 2 x Emotiva UPA-1 Monoblocks, XPA-5, UMC-1 PrePro
Pro-Ject RPM Genie, Carver C2 Phono Preamp