W/o more info, we're shooting in the dark.
Here's my shot:
The the mid-level Pioneer CLD504 is a karaoke LD made in 1994-1995: no digital out. I'd guess your 1992 player doesn't have one either.
IF your player doesn't have a digital out, it may be still possible to retro-fit one.
Costs about $215 ($100 DIY) from this company:
You get DTS and PCM pro-logic/stereo.
You won't get Dolby Digital 5.1 - i.e. TPM. That requires an AC-3 RF output and separate RF demodulator.