[Barman1942]

I recently bought an SMSL SD-973II DAC/AMP for my PC350's and PS4, with a digital RCA cable running from the SMSL to the HT Omega Claro in the rear of my PC and the optical SPDIF cable going to the PS4. However when I connect my headset to the amp and make sure it's set to RCA, I don't get any sound. I tried connecting to my PC with just the optical cable, and there was still no audio. I've made sure the Claro is set to SPDIF/In Loopback in the settings, and I'm not sure where to go from this point.

 

[tcsfny]

I just got the SMSL SD-973II as well.  When connected to a pc with an SPDIF cable, set the pc sound playback device to "digital output" and press the SMSL "select button" so that the leds is "red" (both the power and select buttons will turn red, not sure why).  Sound output from the pc will be from the SMSL headphone jack.
 
I also connected a dvd player coaxial output to the coaxial input of the SMSL, press the select button until the leds is green and the cd will play thru it.
 
I have not tried the regular rca line/in - line/out terminals yet.
Hope it helps.