Digital audio pass-through - RCA LCD

[acollins]

The audio pathways in my home theater are all digital. I have HDMI cables from a PS3, a HTPC, and a satellite box running into my RCA 42" LCD TV (L42FHD37).

The RCA TV has a TOSLINK digital audio out, so I run a S/PDIF cable to an RCA RX-7000 home theater receiver.

I've noticed that the digital audio, as it passes through the RCA TV, loses its encoding (whether it be Dolby Digital, DTS, whatever). This has made me wonder what's going on in the TV as the audio passes through and is switched from the HDMI digital audio to TOSLINK digital. Shouldn't this be a purely digital pass-through, with the digital audio being unaltered? Why is the encoding being stripped? Surely the TV isn't converting digital-to-analog and then analog-to-digital...

This is not a huge deal to me since the receiver just powers two big JBL S310s, and I wouldn't notice much difference with fancy audio encoding anyway.

So everything sounds good, but I'd like to know that all the digital-to-analog conversion is happening in the receiver. I can't find anything on-line about this TV that's nearly technical enough to answer this question.

Any thoughts?

 

[BoredSysAdmin]

This less than optimal, but very typical.
TV rarely pass-thru exact digital dignal, but instead they down-sample it to 2.0 and this is what you getting.

I could only assume your receiver doesn't have hdmi ports?
If you want to experiment - try to connect spdif direct from components (htpc, ps3 and sat box) straight to receiver if it has digital audio inputs.
SPDIF (coax or optical) could handle most current fancy lossless hd formats, but it's restricted Dolby digital and DTS.
If you want to experience lossless hd formats, you must have hdmi 1.3 compatible receiver

 

[MDS]

Any audio that arrives via a digital input is passed to the digital out but the TV may downmix it to 2 channel PCM. On TVs that support outputting Dolby Digital there is usually a menu option that allows you to choose to output DD or have it downmix to 2 channel PCM.

 

[acollins]

So it's the same digital audio signal, but just down-sampled to 2-channel PCM?
I guess I can live with that. As long as it's only being converted once, in the receiver.

Thanks for the replies.