About the sound quality of TVs optical outs

[RayDunzl]

The only thing I've noticed using the optical out of my newish Samsung is the differences in frequency response that comes with different programming over cable.

I haven't stared at it recently, but some programming (cable) might brickwall at 16khz, while commercials between program segments would be full range.

I'll have to send the TV a test tone and see what it does with it sometime, I guess.

 

[gino1961]

The only thing I've noticed using the optical out of my newish Samsung is the differences in frequency response that comes with different programming over cable.
I haven't stared at it recently, but some programming (cable) might brickwall at 16khz, while commercials between program segments would be full range.
I'll have to send the TV a test tone and see what it does with it sometime, I guess.

Hi thank you very much for your very kind and valuable reply/advice
In the meantime, I realized I was making my life difficult. A DAC that costs 20 euros and also has a digital volume control on board must have its limitations. And in fact, after replacing it with a cheap but very decent DAC from SMSL Audio, the difference is quite impressive, still using the same optical output.
I'm obsessed with finding a giant killer that's lasted more than 40 years... and I can't understand why quality has to cost a little in the end.
Thanks again and best regards to everyone.
Gino

 

[solderdude]

Not all DACs perform equally well on SPDIF and TOSLINK.
The reason for that has to do with the receivers used and how the PLL works as well as the quality of the used DAC itself.

SPDIF/TOSLINK signal is processed fundamentally different from USB inputs.
The (derived clock) from the SPDIF/TOSLINK is actually used to 'steer' the internal clock of the DAC.
In USB the 'clock' is not used to sync the internal clock. The data is applied and handled very differently.

So depending on how the DAC (device) is built and how well jitter is suppressed (methods can differ) the derived signal clock of the SPDIF/TOSLINK may be de-jittered in various grades (using different methods).

This is where the price can make a difference and some kind of re-clocking may be (somewhat) useful in certain cases and in other cases it does not.

 

[gino1961]

Not all DACs perform equally well on SPDIF and TOSLINK.

Hi thank you for the very kind and precious advice
It is clear that i have time to waste being retired and i like so much to play with different units and make comparison
My final goal would be to build something analog ... like a line preamp But that needs some time
Just to clarify i was testing this little device
https://amzn.eu/d/3q7e41B
I liked the fact that it has also a digital volume controlled by remote
I replaced it with a more expensive SMSL Sanskrit and the sound is now clearly much better Fuller with much better detail Quite musical
It is impressive how a weak link can ruin all the sound in a system
My main regret is that i don't have instruments to check but I have to listen
There's no going back
I was wasting time

The reason for that has to do with the receivers used and how the PLL works as well as the quality of the used DAC itself.
SPDIF/TOSLINK signal is processed fundamentally different from USB inputs.
The (derived clock) from the SPDIF/TOSLINK is actually used to 'steer' the internal clock of the DAC.
In USB the 'clock' is not used to sync the internal clock. The data is applied and handled very differently.

Very interesting Is there a way to check the quality of the optical input of a dac ? i am focusing only on the tosling connection
My source is a Chromecast Ultra sending the hdmi signal to an audio extractor that outputs an optical signal to a dac
I prefer this solution for streaming because i can stream almost anything from audio concerts and movies
I have not tried if the Chromecast can read files from a NAS Yet

So depending on how the DAC (device) is built and how well jitter is suppressed (methods can differ) the derived signal clock of the SPDIF/TOSLINK may be de-jittered in various grades (using different methods).
This is where the price can make a difference and some kind of re-clocking may be (somewhat) useful in certain cases and in other cases it does not.

Very interesting again I guess that cheap dacs do not reclock the input signal ? this will make dependent also from the quality of the incoming signal
I am sure after all the passages there will be some amount of jitter
I wonder what would be the entry level dac that reclocks the signal I have seen only very expensive units to do this
I will search again
Thank you very much indeed for your very valuable advice

 

[solderdude]

As good as all DACs re-clock.

In case of SPDIF/TOSLINK the DAC needs to synchronize with the incoming data and the clock for that is embedded in the signal (a modulation method).
The 'average' speed of the data needs to be matched to that of the DAC's internal clock.
This is usually done by using some form of PLL.
Depending on how that is done (if a short FIFO memory is used or the internal PLL output is directly used as DAC-chip clock jitter can be removed/lowered.

In the end, for any good DAC with proper jitter rejection the jitter on the analog output is determined by the DACs internal clock and circuitry.
That jitter is inaudibly low and jitter from the data stream does not matter at all. They are essentially decoupled.
So... be careful blaming data jitter as the cause for something that is subjectively perceived as 'lesser sound quality'

It would need to be tested if you want to find out about performance of any DAC.
I don't think those cheap DACs are well suited for music enjoyment but are suited for watching movies etc.
There are plenty of good DACs out there that have excellent SPDIF/TOSLINK performance as good as USB UAC2 these days.
And they don't need to cost a fortune but won't be found in the cheapest segment.

 

[gino1961]

As good as all DACs re-clock.
In case of SPDIF/TOSLINK the DAC needs to synchronize with the incoming data and the clock for that is embedded in the signal (a modulation method).
The 'average' speed of the data needs to be matched to that of the DAC's internal clock.
This is usually done by using some form of PLL.
Depending on how that is done (if a short FIFO memory is used or the internal PLL output is directly used as DAC-chip clock jitter can be removed/lowered.
In the end, for any good DAC with proper jitter rejection the jitter on the analog output is determined by the DACs internal clock and circuitry.
That jitter is inaudibly low and jitter from the data stream does not matter at all. They are essentially decoupled.
So... be careful blaming data jitter as the cause for something that is subjectively perceived as 'lesser sound quality'
It would need to be tested if you want to find out about performance of any DAC.
I don't think those cheap DACs are well suited for music enjoyment but are suited for watching movies etc.

Thank you very much again I understand the complexity of the issue I only knew about the difference of syncronous and asyncronous dacs
I am stuck to toslink connection for the reasons i mentioned In the next days i will rotate some dacs i have at hand

There are plenty of good DACs out there that have excellent SPDIF/TOSLINK performance as good as USB UAC2 these days.
And they don't need to cost a fortune but won't be found in the cheapest segment.

Well now i have really to ask what could be a decent entry level unit ? the goal is to exit from the dac with a musical signal
I like the fact that with a chromecast i can stream both video and audio And it costs next to nothing Expecially 2nd hand
I wonder how it is not more popular ... it will be always possible to invest more money on the dac
Thanks a lot again

 

[solderdude]

The SMSL you have is fine.
The cheap one you linked to is fine for TV but would not recommend for music enjoyment.

I use an even cheaper optical-> analog converter for my TV to my stereo... it 'works' and only now and then needs a 'reset'.
The type that Amir also tested.

 

[gino1961]

The SMSL you have is fine.
The cheap one you linked to is fine for TV but would not recommend for music enjoyment.

I use an even cheaper optical-> analog converter for my TV to my stereo... it 'works' and only now and then needs a 'reset'.
The type that Amir also tested.

Thank you sincerely for your kindness and extremely valuable advice
It was important to me to fix some points
i will move my attention to the preamp
Kindest regards Gino

 

[gino1961]

Hi thank you for the very kind advice
Now I am using a Chromecast Ultra as audio and video streamer
I use the tv only as video monitor