LG TVs Optical Audio Output Issue (poll)

Have you experience audio drop-outs with an LG TV when using optical?

  • Yes

  • No


Results are only viewable after voting.

ostewart

Well-known Member
I've been having a discussion with a brand who make external DAC's, and they have some interesting findings on the optical output of LG TV's.

Firstly I had audio drop-outs when using my C9 55" with a Cambridge Audio CXA81 - a firmware update and cable sent by Cambridge Audio fixed this issue but they didn't exactly go in to detail as to what caused the problem in the first place.

The new DAC I have now, hooked up to the same TV, is also experiencing drop-outs, and the brand have gone in-depth and bought an LG UN7300 model to test - they hooked it up to their APx555 analyser and there are some issues.

I'm just curious with the stream set to PCM into an external DAC via optical SPDIF - who else has had issues?
 

Lapstre

Active Member
I voted no, as I've never had audio dropout issues. But I wonder what kind of processing/conversion LG does when I set audio to PCM, and does that lead to my perceived loss in sound quality vs my pi streamer.
 

ostewart

Well-known Member
I voted no, as I've never had audio dropout issues. But I wonder what kind of processing/conversion LG does when I set audio to PCM, and does that lead to my perceived loss in sound quality vs my pi streamer.

If you're using standard optical output in PCM you will likely be getting lower quality.

May I ask what DAC chip is in the device you are using?
 

ostewart

Well-known Member
I experience audio dropouts outputting a bitstream to a Tag Maclaren Av32R

Thanks for this, from the manufacturer I know the issue mainly lies with ESS DAC chips, and it has to do with their jitter reconstruction tech. If the tolerance is set low - and isn't forgiving of jitter - this is when drop-outs occur. Changing the firmware so it is more forgiving does have a slight impact on sound quality, and allows more jitter through, but this means fewer dropouts.

Is there a better way? Extract via an HDMI splitter? I use the pi when streaming, but would be good to use the TV as a display.


The manual or search didn't help. Is there a way to find out?

What are you running the optical output in to? (model of the AVR or DAC)

Not sure if a HDMI splitter will be better, but it's possible.
 

TheCrow

Active Member
When I first got my old B6 4 or 5 years ago I had audio dropouts using optical, but this was recognised by LG and fixed with a firmware update. Not had any problems since.
 

Lapstre

Active Member
What are you running the optical output in to? (model of the AVR or DAC)
Oh! My bad!
I use a Cambridge Audio CXA60 as my stereo amp with a Wolfson WM8740 dac.

My pi streamer outputs to Optical as well, but Spotify streamed over pi sounds better vs Spotify from the LG tv app...
 
Last edited:

ostewart

Well-known Member
When I first got my old B6 4 or 5 years ago I had audio dropouts using optical, but this was recognised by LG and fixed with a firmware update. Not had any problems since.

That's interesting, as from the measurements I've seen it looks like the optical output on LG TV's is incredibly poorly implemented - not sure if that can be fixed by firmware.

Oh! My bad!
I use a Cambridge Audio CXA60 as my stereo amp with a Wolfson WM8740 dac.

My pi streamer outputs to Optical as well, but Spotify streamed over pi sounds better vs Spotify from the LG tv app...

It mainly seems to be an issue with ESS chip DACs and their jitter reconstruction filters. LG TV's have some of the worst jitter measured by the company making the external DAC.

"the LG's digital stream is exceptionally noisy--one of the worst streams I've seen."

"I'll admit the pauses are jarring. This is the result of the ESS's otherwise excellent jitter recovery logic. The patented jitter eliminator must periodically unlock and re-sync because the digital stream is so poor. Our older AKM receivers are not asynchronous, so they pass along any significant jitter from an optical source, thus, eliminating any chance of a momentary pause of the digital lock (something that is quite rare). Under typical circumstances, the ESS's async jitter elimination results in dramatically higher performance. The AKM receivers have no jitter elimination, so they pass along any digital stream errors without disrupting the digital lock."

"Jitter measurements are not bad, rather, they've added extreme noise at n*100Hz directly into the digital stream. It's either some type of common mode noise feeding into a digital circuit, or a serious firmware issue. It's bizarre to see spurious transients across the entire audio band."
 

DrDarren

Novice Member
That's interesting, as from the measurements I've seen it looks like the optical output on LG TV's is incredibly poorly implemented - not sure if that can be fixed by firmware.

It mainly seems to be an issue with ESS chip DACs and their jitter reconstruction filters. LG TV's have some of the worst jitter measured by the company making the external DAC.

"the LG's digital stream is exceptionally noisy--one of the worst streams I've seen."

"I'll admit the pauses are jarring. This is the result of the ESS's otherwise excellent jitter recovery logic. The patented jitter eliminator must periodically unlock and re-sync because the digital stream is so poor. Our older AKM receivers are not asynchronous, so they pass along any significant jitter from an optical source, thus, eliminating any chance of a momentary pause of the digital lock (something that is quite rare). Under typical circumstances, the ESS's async jitter elimination results in dramatically higher performance. The AKM receivers have no jitter elimination, so they pass along any digital stream errors without disrupting the digital lock."

"Jitter measurements are not bad, rather, they've added extreme noise at n*100Hz directly into the digital stream. It's either some type of common mode noise feeding into a digital circuit, or a serious firmware issue. It's bizarre to see spurious transients across the entire audio band."

Thanks ostewart, I think you're the first to describe and explain the problem that I'm having and I have spent many hours searching, assuming I cannot be alone with this issue.

I have been using optical out into an external DAC using the ESS Sabre chip (can I name the DAC here?) and had zero problems with Panasonic EX700 LED TVs, but upgraded to the LG OLED 48CX5LC in February this year and immediately noticed audio dropouts. Sometimes it can go hours without any dropouts, other times I get dropouts every 5 minutes or so. As you describe the dropouts are very jarring and so extremely annoying.

As my external DAC also acts as my pre-amp, I cannot revert to using analogue audio output from the LG, and besides, that seems so last century. Is there any indication of a potential fix for ESS chip DACs? At the moment, I'd accept a drop in quality to reduce the number of dropouts. I guess another alternative is routing the LG signal via an different DAC, but not sure I then feed that into my DAC/pre-amp?

DrDarren
 

ostewart

Well-known Member
Thanks ostewart, I think you're the first to describe and explain the problem that I'm having and I have spent many hours searching, assuming I cannot be alone with this issue.

I have been using optical out into an external DAC using the ESS Sabre chip (can I name the DAC here?) and had zero problems with Panasonic EX700 LED TVs, but upgraded to the LG OLED 48CX5LC in February this year and immediately noticed audio dropouts. Sometimes it can go hours without any dropouts, other times I get dropouts every 5 minutes or so. As you describe the dropouts are very jarring and so extremely annoying.

As my external DAC also acts as my pre-amp, I cannot revert to using analogue audio output from the LG, and besides, that seems so last century. Is there any indication of a potential fix for ESS chip DACs? At the moment, I'd accept a drop in quality to reduce the number of dropouts. I guess another alternative is routing the LG signal via an different DAC, but not sure I then feed that into my DAC/pre-amp?

DrDarren

Glad I'm not the only one, and yes you can quote what DAC chip is used and what the device you are using is.

There is indeed a fix, but it depends on if the manufacturer of the DAC you are using is willing to work on firmware to fix it.

My latest DAC has had an updated firmware put on and now there are no drop-outs.
 

DrDarren

Novice Member
Thanks ostewart. I’m feeding my LG OLED CX into an Audiolab M-DAC/ESS Sabre32 9018 which feeds into an M-PWR power amp. Are all Sabre chips affected or just the 9018 series?

DrDarren
 

ostewart

Well-known Member
Thanks ostewart. I’m feeding my LG OLED CX into an Audiolab M-DAC/ESS Sabre32 9018 which feeds into an M-PWR power amp. Are all Sabre chips affected or just the 9018 series?

DrDarren

I'd contact Audiolab and let them know that both Cambridge Audio and JDS Labs have had to offer up firmware which relaxes DPLL bandwidth - bandwith of 15 gets rid of it, I am now going to be testing bandwidth of 11 to see if that works too. The stock was set at 10 which caused dropouts.

9018 and 9016 chips are what I've used and had issues with.
 

DrDarren

Novice Member
So overnight I ordered an iFi iPurifier2, which is a reclocker that will supposedly reduce the jitter on the LG CX TV optical output. But I might have just wasted £200...

Then today I just stumbled across a post mentioning there is already a jitter bandwidth setting in the Audiolab M-DAC menu! It's just not documented in the official manual as it was added in a later firmware update. :-( It can be set separately for OPT 1 and OPT2, so just made the change to HIGH (LOW/MEDIUM/HIGH and AUTO options) and will post back on how I get on. There's so little info out there on this annoying problem!

I found another post with the same issue with an Arcam SA10/ESS 9016K2M and an LG TV. The Arcam SA10 has a menu setting to set PLL to wide that fixes the problem. But I only found that after ostewart mentioned DPLL yesterday.

DrDarren
 
Then today I just stumbled across a post mentioning there is already a jitter bandwidth setting in the Audiolab M-DAC menu! It's just not documented in the official manual as it was added in a later firmware update. :-( It can be set separately for OPT 1 and OPT2, so just made the change to HIGH (LOW/MEDIUM/HIGH and AUTO options) and will post back on how I get on. There's so little info out there on this annoying problem!
I have an Audiolab 6000A stereo pre/power amplifier and can confirm that the 'digital jitter selection' feature was included with firmware v0.28, released 31 Oct 2019.

I've never used the optical connection from my 2016 LG television so I can't comment how effective this new feature is...
 

Edwood

Active Member
I did experience audio drop outs on an Audiolab 6000A connected by optical to my LG 49SM8600 and setting PLL to wide has fixed the problem for me.
 

DrDarren

Novice Member
I can confirm that after around ten hours of use, setting jitter bandwidth to HIGH (from AUTO) on my Audiolab M-DAC I no longer get audio drop outs on my LG 48CX TV optical output. Hurrah! Only taken 6 months to figure this out…. Finally, I can enjoy my LG TV as intended.
 
I can confirm that after around ten hours of use, setting jitter bandwidth to HIGH (from AUTO) on my Audiolab M-DAC I no longer get audio drop outs on my LG 48CX TV optical output. Hurrah! Only taken 6 months to figure this out…. Finally, I can enjoy my LG TV as intended.
That's great news ;)
 

ostewart

Well-known Member
I can confirm that after around ten hours of use, setting jitter bandwidth to HIGH (from AUTO) on my Audiolab M-DAC I no longer get audio drop outs on my LG 48CX TV optical output. Hurrah! Only taken 6 months to figure this out…. Finally, I can enjoy my LG TV as intended.

That's great :D
 

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