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Noisy digital audio on LG TVs

JunkHippo

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Dear audio science enthusiasts,

I recently got one of those popular LG C1 TVs. Since I only have a stereo system, but several HDMI sources plus using the TV's apps, I went the easiest audio route for my setup:
(source) -> TV -> optical out (PCM) -> DAC -> analog Preamp
As I realized only after my purchase, the optical out of LG TVs seems to be quite terrible (noisy) across models and LG seems to not care about it. Most clearly it's stated in an FAQ by JDS Labs, who measured SINAD of 81db from one LG TV. Quite a few people complain about stuttering audio as well, coming from some DAC's jitter handling not "expecting" such a terrible source signal. Now my DAC doesn't have that problem*, but I'm still curious if using an HDMI audio extractor may yield a better signal.
So my question is if anyone has tested or seen this measured for LG TVs in particular: optical out vs extracted from ARC HDMI?
I've seen at least one report where people have tried the extractor route without solving their stuttering audio problem, which leads to the question if LG has only messed up the optical output or digital audio output in general.

Here's a thread from AV Forums about the topic.

* DAC is a Lake People RS-06, which the manufacturer claims has a resampling and re-clocking implementation that "almost completely rejects jitter". I have no idea to which % this is marketing mumbo jumbo, but at least I get no interruptions to audio.
 

Beershaun

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HDMI out over arc works fine for me no stuttering when plugged into my Denon AVR. I don’t know if the SNR is lower. I expect not since HDMI is notorious for transmitting noise.
 

delta76

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Your tv supports eArc, not sure why you are using optical out.
optical out implementation on TV could be a hit or a miss, and I usually see that as the "last resort".
 
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JunkHippo

JunkHippo

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Your tv supports eArc, not sure why you are using optical out.
Because I use a DAC (not an AVR) and those tend to not have HDMI inputs. Until reading about the LG case, I wasn't even aware of poor optical implementations on TV. My old Sony was fine.

I might try an audio extractor, although those tested here with good results are not readily available in EU. Still looking for a good choice.
 

DVDdoug

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who measured SINAD of 81db
-81dB isn't that bad. We would have killed for -81dB in the analog days!

If it's really a digital problem it's likely worse than that and caused by dropouts or glitches (corrupted digital data). Regular jitter is "never" audible.

Have you tried the analog output (headphone output?). If might be better and It might be perfectly acceptable.
 

SpaceMonkey

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Dear audio science enthusiasts,
...

* DAC is a Lake People RS-06, which the manufacturer claims has a resampling and re-clocking implementation that "almost completely rejects jitter". I have no idea to which % this is marketing mumbo jumbo, but at least I get no interruptions to audio.
Interesting DAC.
If you are not experiencing any dropouts I would not bother much.
Otherwise get something like this and see if it is any better:


You can return within 30 days and get full refund.
 
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JunkHippo

JunkHippo

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Have you tried the analog output (headphone output?). If might be better and It might be perfectly acceptable.
Perfectly reasonable! It's just that I have this fancy DAC here and would like to make use of that, ideally feeding it a good signal. But the TV's analog out may of course be OK.

Otherwise get something like this and see if it is any better:
That's my current plan, just try one of those budget options.
It's probably more for peace of mind anyway, like having one of the best measuring DACs even when the differences are beyond threshold of hearing.
 

lennyanders

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I'm currently in kinda the same boat. I use an optical to coaxial adapter and then a coaxial to XLR AES/EBU cable into my Genelec's and the experience is horrible.

In the AV Forums thread I read that some even had problems with eARC, but I hope that these are just some minor things like some not supported formats. I only need stereo.

These cheap adapters mostly only support ARC and not eARC, which isn't fully backwards compatible, I think.

I will probably just go with a BlueSound Node. I planned to get something like that anyway and just didn't want to throw the money out now, but If it helps, it's worth it for me.

So yeah, I will probably order that today and pray that it just works.
 

lennyanders

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Hey, I ordered the bluesound a bit later when I thought, because I contacted the Genelec support (the speakers with which I had the problem). They are still looking into it, and so I ordered it because I wanted it fixed this week.

I'm glad that I can say that it totally fixed my problems. I needed to disable the "Audio clock trim" function, but after that everything was perfect.

Furthermore, I would still like to know if these cheap adapters do the job too. Did you already get one @JunkHippo?
 
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JunkHippo

JunkHippo

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Furthermore, I would still like to know if these cheap adapters do the job too. Did you already get one @JunkHippo?
Not yet, I may order one in the next days. For my setup, it's less of an acute problem: I have no sound dropouts and it doesn't sound horrible. It's just a slight feeling that it could be better (compared to my other digital source), and that is most likely biased from having read about the lacking quality of the TV's optical out, whether audible or not.
I'll make sure to report my experience here in the thread. Will probably get the second one that @SpaceMonkey suggested because it's cheap and fits exactly my use case (don't need DAC, headphone out, video passthrough etc).
 

Rottmannash

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I cannot discern a difference between optical and HDMI from my C9.
 

pvehling

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Some DACs have issues with LG OLED's optical port using PCM. I've tested a C8 and C9 with around 8 DACs and the Toppings all had pops and clicks, my current SMSL I think I only heard a pop one time. Schiit Modi 3 was fine also, but one other brand had pops like the Toppings (forgot which one). Also, make sure any HDMI device like a Firestick or Roku is set to PCM in the audio settings.
 

Juhazi

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JunkHippo, have you gone through all the sound settings of your LG tv? Every automatic compession, limiting, eq, loudness etc. settings must be disabled!
 

SpaceMonkey

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Some DACs have issues with LG OLED's optical port using PCM. I've tested a C8 and C9 with around 8 DACs and the Toppings all had pops and clicks, my current SMSL I think I only heard a pop one time. Schiit Modi 3 was fine also, but one other brand had pops like the Toppings (forgot which one). Also, make sure any HDMI device like a Firestick or Roku is set to PCM in the audio settings.
In my experience, all the most terrible toslink devices worked just fine with lg toslink output. currently tv is connected to a cheap 4 way optical switch. no issues at all.
 
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JunkHippo

JunkHippo

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@pvehling : Thank you for confirming that this is an issue for some! You didn't try an (e)ARC audio extractor with these TVs and DACs by any chance?
As stated in the link to JDS Labs in my original post, the issue depends on how the DAC handles jitter from the TV's optical port. Quoting from that link:
In short, the optical output of symptomatic TVs show pronounced jitter and low level n*100Hz transients throughout the audible frequency range. The default jitter rejection values used by ESS based DACs recognize the extreme noise as signal errors, so the DAC automatically disconnects and reconnects in attempt to achieve a more stable lock of the incoming S/PDIF signal.

This behavior 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. AKM and Wolfson S/PDIF receivers are not asynchronous, so they pass along any significant jitter from an optical source, thus, eliminating any chance of a momentary pause for an S/PDIF re-locking event.
I'm trying to find out if it's only the optical port implementation that's faulty or LG's digital audio procecssing in general.

Since I don't have the audio dropouts or pops on my DAC, I can't check if the HDMI connection eliminates these problems, and I also don't have the necessary measuring equipment. I could listen, but I doubt the difference will be audible in the end.
 

lennyanders

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I had massive dropout problems using optical to coax to AES/EBU (genelecs, which use AKM chips, I think) which disappeared using eARC into Bluesound Node. But I don't know if it is the eARC that makes the difference or the Bluesound Node itself. I could try using the optical out of my TV to connect to the Bluesound Node this week to check that.

If you don't have hearable issues using your optical out, I don't think eARC makes an acoustic difference.
 

SpaceMonkey

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Once I tried a stupid passive optical splitter (1 optical in > 2 optical outs) and there were lots of pops down the line. So i think overall toslink out on LG is not only noisy but also weak in power (if optical output power is even a consideration here) . and this was gone as once it was connected to an optical switch, i guess optical repeater might work as well.
 

pvehling

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@pvehling : Thank you for confirming that this is an issue for some! You didn't try an (e)ARC audio extractor with these TVs and DACs by any chance?
As stated in the link to JDS Labs in my original post, the issue depends on how the DAC handles jitter from the TV's optical port. Quoting from that link:

I'm trying to find out if it's only the optical port implementation that's faulty or LG's digital audio procecssing in general.

Since I don't have the audio dropouts or pops on my DAC, I can't check if the HDMI connection eliminates these problems, and I also don't have the necessary measuring equipment. I could listen, but I doubt the difference will be audible in the end.
That makes sense. From what I remember, most of the DACs that had issues were relatively new and ESS-based! But after I swapped the mainboard in my C8 to the C9, the optical using PCM was definitely better with far fewer pops than before. The C9 supports bitstream and all that over optical whereas the old C8 board didn't.
 

HedgeHog

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I run my LG OLED back out via TOSLink to my pre-pro (too old to have eARC) and I don't experience noise or poor quality. Sounds quite good, imho. I use this strictly for the apps that's on the TV (Disney+, Netflix, AppleTV, etc) to use my system for audio. For regular viewing, I use the TV's speaker. For BD playback, I go from BDP to pre-pro to HDMI in.

The pre-pro is running some ancient TI chip, so not even the later ESS stuff. FWIW.
 
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