Poor sound quality via TV optical output

[EdTice]

Dumb question, with potential apologies in advance, but did you take the plastic caps off the optical connectors? I have known lots of people not realize they have to.

I have forgotten to do this before and lost quite a bit of time figuring out why there was no audio. But I've never had the audio pass through poorly. Are caps sometimes translucent enough to pass a degraded signal?

 

[krabapple]

Interesting. I did not know this was possible. Thank you. The plot thickens for the OP. If the TV is trying to pass-through 5.1 audio via TosLink and the DAC doesn't support the format?

S/PDIF (optical or coax) has always been able to do this, from any source I can think of. Dolby or DTS bitstreams work fine. Substitute "cable box" for "TV" if that's the source (i.e. cable TV vs streaming TV). Though I suspect few if any cable boxes off optical or coax S/PDIF out these days....I've been using HDMI for so long I haven't bothered to check. If they don't , and you want to decode surround encoded cable TV with your AVR via a TV optical out, your TV has to have a 'passthrough' option to the optical out (it might also be called bitstream/raw).

 

[EdTice]

S/PDIF (optical or coax) has always been able to do this, from any source I can think of. Dolby or DTS bitstreams work fine. Substitute "cable box" for "TV" if that's the source (i.e. cable TV vs streaming TV). Though I suspect few if any cable boxes off optical or coax S/PDIF out these days....I've been using HDMI for so long I haven't bothered to check.

I haven't used an optical cable since Yamaha updated the firmware in their receivers so that eARC worked. Has to be at least half a decade. But I'm pretty sure that most two-channel DACs wouldn't know what to do with a 5.1 signal as they don't have the decoding logic (if for no other reason than not wanting to pay the licensing fee if they only have two channels of output). So I still have no idea what would happen if such a signal were fed to one. This is just a matter of curiosity for me. But I still promote the solution of going to HDMI and a proper AVP now that they are cheap

 

[krabapple]

If the DAC device has no Dolby/DTS decoding capability at all, I would guess the output would be white noise or silence.

What can also happen is the TV has a Dolby decoder (modern ones do) , which if it senses the output will be stereo, downmixes incoming 5.1 bitstreams to 2.0 , which can go out via optical (probably as PCM). Such downmixing can be an iffy proposition, depending on the metadata in the source (mixing engineer's downmixing choices). But that's true of downmixing taking place in an AVR too.

 

[krabapple]

actualy Dolby Digital is enconded into 2 channels, the decoder recreates the multi-channels.
So SPDIF just passes the signal through.

Dolby Digital - Wikipedia

en.wikipedia.org

Can you please quote the section of the Wiki that you think is pertinent? I don't get what you are trying to say here. AIUI, Dolby Digital surround channels are not 'matrixed' into 2 channels, like the old quadraphonic SQ and QS formats were. A multichannel Dolby Digital mix is *downmixed* to two channels upon decoding if the playback system is two channel. S/PDIF can pass either the undecoded multichannel lossy compressed bitstream or a downmixed 2-channel PCM decode of a 5.1 Dolby Digital source.

 

[dasdoing]

Can you please quote the section of the Wiki that you think is pertinent? I don't get what you are trying to say here. AIUI, Dolby Digital surround channels are not 'matrixed' into 2 channels, like the old quadraphonic SQ and QS formats were. A multichannel Dolby Digital mix is *downmixed* to two channels upon decoding if the playback system is two channel. S/PDIF can pass either the undecoded multichannel lossy compressed bitstream or a downmixed 2-channel PCM decode of a 5.1 Dolby Digital source.

yea, it was bullshit...deleted my coment

 

[Deleted member 23424]

For what it's worth... I have a £1200 Panasonic Vieira TV that delivers exactly the same as the OP. I've tried everything, no luck, resigned myself to mediocre TV audio.

I'm simply going optical out into a Topping D90 into a power amp. Everything is 48hz and feels like the freq extremities are rolled off and everything sounds flat and lifeless.

Some apps do seem slightly fuller (eg Amazon) whereas the most heavily used apps (BBC and domestic TV) sound terrible.

I've tried everything re settings, optical is my only out, no joy.

Only solution I can think of is to try the optical/coax out of a TV box of some sort into the DAC, which somewhat negates the intentions of the purchase of the expensive Freesat/Freeview TV to reduce boxes and cables.

 

[ZolaIII]

@dOSs on what power amplifier (excuse me again)? As I have similar Panasonic TV.

 

[Deleted member 23424]

@dOSs on what power amplifier (excuse me again)? As I have similar Panasonic TV.

Purifi, from Boxem.

Music via Pi into USB of the same DAC is glorious.

58 inch 4K UHD TV with HDR | Panasonic UK & Ireland

Explore the stylish 58" TX-58DX802B Panasonic UHD 4K TV with HDR - Tuned by filmmakers to deliver breath-taking colour quality, contrast and brightness.

www.panasonic.com

Specs here

 

[ZolaIII]

@dOSs I have GX810E paird with Yamaha R-N402D (Burr DSD1791) and don't percept having such problem. I mean I do bost slight both ends up when listening at lower loudness lv (and even use some of the processing options on TV side). It is fixed at 48 KHz but that's to be expected with video broadcast. Very little of broadcaster's does the signal processing as they should (mostly EU one's) meaning before all EBU R128 loudness normalization. Try to feed the DAC from another Toslink input and see what happens.

 

[Deleted member 23424]

@dOSs I have GX810E paird with Yamaha R-N402D (Burr DSD1791) and don't percept having such problem. I mean I do bost slight both ends up when listening at lower loudness lv (and even use some of the processing options on TV side). It is fixed at 48 KHz but that's to be expected with video broadcast. Very little of broadcaster's does the signal processing as they should (mostly EU one's) meaning before all EBU R128 loudness normalization. Try to feed the DAC from another Toslink input and see what happens.

CCA into D90 optical sounds good.
TV into the same doesn't.

It's the 'smart' TV.

 

[ZolaIII]

To me mine sounds pretty same when I fead it trogh USB to ESS 32 DAC and analog to amp or trogh HDMI to TV and Toslink to amp (playing from PC). For music over USB it sounds better but that's more related to extend reprocessing chain I use.
Panasonic OS is as dumb as they get this day's which I actually like. I don't know what's problem with yours (if it sounds different from different Toslink outputs into the same DAC Toslink input).