[AirForceTeacher]

I have a Vizio TV that I use for TV (Tivo), TV Computer and BluRay.  For ease of use for the SO, I run everything to the TV via HDMI, so she only has to use one remote to switch inputs, volume, etc.  There's an optical out from the TV to the receiver.  Just out of curiosity I put a new CD in the BluRay player and connected an optical from the player to the receiver.  When I A/B'd them, the optical from the player sounded better and was at the least louder.  I had (naively) assumed that digital was digital was digital, and that the audio over HDMI would be same bitstream as the SPDIF. 
 
So, it seems one of the following happened:
 
1. HDMI is bit-perfect, but my TV converted it somehow (D->A to the internal audio mixer, then A->D from the internal to the optical out)
2. HDMI isn't bit perfect
3. Pixies
 
Anyone ever try this before? Next step I guess would be to go HDMI from the BluRay to the receiver, then A/B it again.
 
EDIT: I've had no other sound issues with the TV - in fact, watching something from Netflix the other day, I swear I heard soundstage for the first time ever:  I have no surround sound set up at all, yet I heard a telephone ring at least a foot or two to the right of the speaker. Freaked me out - I was looking at the top of the fireplace looking for a phone!

 

[Jon L]

Quote:

So, it seems one of the following happened:
 
1. HDMI is bit-perfect, but my TV converted it somehow (D->A to the internal audio mixer, then A->D from the internal to the optical out)
2. HDMI isn't bit perfect
3. Pixies

Both HDMI and spdif (rca and toslink) simply were not designed with audio quality in mind, as neither has a separate line for the all-important audio clock.  This critical timing information has to be separated out from data at some point in order to form music.  There are multiple parts (usualy very cheap parts in these consumer products) involved in the HDMI->toslink process that can screw up this delicate process, resulting in increasing jitter, thus worse final sound.  There may even be some grossly underperforming parts that actually result in non-bit-perfectivity, resulting in lower volume, etc. 
 
In general, less stages/parts you can go through, the better IME.