Bartok and Rossini dac problem using optical connection

have an interesting problem that i couldnt solve whatever i tried: my LG 65C8 tv is connected to Rossini Player with an optical cable and every 30-40 minutes i have sound switching off for like a sec and the dac makes the click sound that it usualy do when loosing connection. Same problem with my previous Bartok dac.
no external clock is used.
i changed optical wires, changed the tv, Changed Bartok to Rossini- the problem stays. Changing clock settings in the dac from Master to Audio makes the problem even worse- the soun dropouts every several minutes.
is it a known issue? are there any solutions?

This appears to be a synchronisation issue. However you have so far:

  1. Tried all dCS DAC clock synch settings to no avail.
  2. Tried 2 different DACS.
  3. Tried different TVs.
  4. Tried different connecting cables.

All offer no solution.

Are you able to listen to the TV’s sound direct ( not via a DAC and your audio system) with no problems e.g. through its speakers or using headphones plugged into the TV? Is the programme source the TV itself or is it being fed by something else e.g.a streaming service including TV catch up apps, a TV box or a DVD player? I am just speculating here that as you seem to have tried every different combination from TV to DAC could you be experiencing something being passed forward through the chain from the original source? I would have imagined that buffering somewhere should have dealt with such a possibility but let’s not rule it out yet.

I am assuming that you have specifically changed the synch settings for the optical input, they are not universal. I am sure that you know that but it just occurred to me as something to check…

the problem in both netflix and built in TV satelite reciever.
actually there is no sync options on tv except pcm\auto option, but changing that didnt help, also Netflix wont work with “auto”

Thanks. So it seems that the source is the TV itself rather than an external box feeding it. But you say that you have already tried a different TV and had the same problem.

I wonder if someone from dCS can suggest a solution?

The correct configuration on your LG TV is for “Digital Sound Out” to be PCM. While the correct Sync Mode setting on your Bartok/Rossini is Audio (so that the DAC’s is sync’ed to the incoming TV PCM bitstream).

With those settings, if you’re experiencing drop-outs, then I’d venture a guess that your LG TV is outputting digital silence every now and then, and the DAC has to re-sync when the TV streams audio again out of silence - you can verify that this is happening if you observe the incoming bit-rate on the DAC, if it periodically goes to 0, then you know for sure your TV’s outputting digital silence.

I don’t think there’s a simple fix for this, the DAC is behaving as it should.

When you swapped the TV for a different one, was this an identical model (LG 65C8) or was it a different model?

Do the dropouts occur in the middle of a stream, when you change stream, or both? For example, changing channel on the SAT receiver?

Netflix does do some strange stuff with regards to output signals when you’re browsing the menu, so I would expect the DAC to need to re-lock when moving between titles on the menu if they’re set to autoplay a trailer.

  1. tv’s were same model
  2. in the middle of the strream- you are watching some program and get dropouts in Master mode every 30-40 mins, audio mode every 2-3 mins

i did try connecting tv to oppo 203 by hdmi in arc mode and then by optical cable from Oppo to Rossini- no problem.

Your dCS DAC is fine with an optical connection to the Oppo. The Oppo is fine with an HDMI connection to the TV. You have tried two samples of the same model TV and the same problem of optical connection to two different DACs occurred using either TV .This accordingly suggests that there may be an issue with the way that LG has implemented the tv’s PCM optical output. Everything else seems to be working OK.

I think Pete hit the nail on the head, it very much seems as though the optical output of the TV is the source of the issue here. Running audio over ARC to the Oppo and using optical from there causes no issue, and having two TVs of the same model show the same behaviour suggests that it’s not something faulty with the individual TV unit itself.

Running the audio through the Oppo seems therefore to be a valid workaround.

The pauses in audio are a result of the dCS unit receiving a bad signal from the TVs optical output, and needing to re-lock periodically to maintain audio. I think it’s likely the LG is outputting a slightly incorrect sample rate over optical, but seemingly not via ARC.


I’m having similar issues with my recent LG TV optical out to my Rossini. The Rossini intermittently locks (and I hear audio momentarily) for a second or 2 then toggles (lock/unlock)?

Initially, I thought the TV was faulty, and so have just swapped it for a second new one. The problem remains. In summary, I cannot use the SPDIF optical input of the Rossini with my TV.

Is there anything one can do to get this working?

The previous thread on this subject ended with the conclusion that LG have implemented the optical output in such a way that it is not compatible with the dCS input . Other devices do work perfectly well with the dCS optical input thus adding strength to this conclusion. The fact that now you too have exactly the same problem as the original poster with these TVs serves to emphasise that the problem ( and solution) lies with LG.

If the TV is new is it possible to exchange it for another make? Depending upon consumer law in whatever country you reside in you may be able to return it as unfit for purchase as it does not perform as its specifications indicate .

The only workaround that I can think of is to buy a hard drive TV recorder ( with an optical or other sound output port and not LG) and connect that to the DAC via the spdif or toslink port with its HDMI port feeding your TV from the recorder’s tuner. So you will be using the LG’s screen but everything else will be from the recorder in “watch” rather than "record "mode (if live TV broadcasts are what you want). Unfortunately though AFAIK these recorders are not smart so maybe no Netflix or other streaming ( could you plug a Roku stick into one?). It’s all a bit Heath Robinson ( Rube Goldberg if you are American) and I think another TV may be the cleanest solution.

I hear what you are saying Pete, and indeed I will look into a change of TV manufacturer.

However, in reality, LG will be manufacturing literally many thousands/millions of TV’s in comparison to a very small number of dcs DACs…

To me, therefore, I would conclude that this problem resides with dcs to determine a fix for :slight_smile:

As far as we can deduce, because every other make of equipment with an S/Pdif toslink output appears to work without difficulty into a dCS DAC the way LG has implemented this interface seems to be unique. If dCS made their input to work with it then the other side of the coin would probably be that nothing else will. So it wouldn’t work with TVs from Sony, Samsung, Panasonic, Toshiba, B&O, Philips etc, the total production of whom exceeds that of LG ( even if LG makes the OLED panels for many of them :wink:). Nor would it work with non-video devices that require a toslink input.

Further, it may be that the way LG has implemented that output could be an error. If it is a software fault they could/may release an update. BTW therefore worth running an update search from time to time if you keep it.

I don’t think myself that dCS changing their input configuration to suit a single third party brand would be a good decision for them especially because as you correctly say they don’t make huge amounts of equipment . And that equipment is owned by a small number of people of whom I can realistically guess that a very small percentage will wish to run it with a 2019/20 season LG TV. So far only 2 are known :slight_smile:

I have since tested the LG optical out with a couple of DAC’s - including NAIM and HDMI ARC to Analogue - and these all work perfectly!

I’m sorry Pete, but your explanation just does not hold.

Thanks adm95. That adds some knowledge.

So we now have the TV that will work with all DACS except one and the DAC that will work with all TVs except one. :wink:

Kind of reminds me of the remark by Peter Walker ( Quad) when he first met Julian Vereker( Naim). " Ah the maker of the speaker that blows up amps meets the maker of the amp that blows up speakers"

Explanation: The very early Naim amps were not too stable into the ESL load and the ESL could be damaged because the Naim 250 could out output in excess of + - 33v which burnt holes in the speaker panel.

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Well the facts are that I have 2 very inexpensive DACs - that seem to have no problem - and I have a very expensive DAC that doesn’t seem to work…

You can’t argue with the facts.

Hi all,

dCS products use Voltage Controlled Crystal Oscillators (VCXOs) with a sync range of +/- 300 parts per million. If a source is outputting a signal which is outside of this range into the dCS product, the dCS unit will continuously drop and re-lock to the signal. This is because the VCXO cannot physically lock to a signal this far out of range. It is worth noting that this is the first time in 20+ years of using VCXOs of this spec that we have come up against this issue.

It may be observed that some devices can synchronise to the same source without issue, however this should not be taken as a direct comparison. Many other devices use different methods of synchronising to a source. For example, SPDIF receivers and PLLs typically use a Voltage Controlled Oscillator (VCO) instead of a VCXO, which has a much wider range that it can accept but equally it introduces more jitter into the signal. This compromises the performance of the system compared to a VCXO, whether the source is properly clocked or not.

We do not feel that sacrificing the performance of the entire system to bring compatibility with sources outputting out-of-range signals is a compromise that should be made in a dCS digital system. As such, we opt to retain high-quality clocking with a slightly more specific sync range. While this means you may get dropouts using sources outputting inappropriate signals, it retains the expected quality from the system when using a well clocked source.


Will an external clock for rossini help with this issue?

As James explained the problem is not with the dCS DAC but with the TV’s digital output which has been produced with a synch range that lies outside of that for which the DAC is engineered so that the DAC is unable to achieve lock properly. The DAC should not be re-engineered to cater for this particular TV set or brand as this would then compromise its performance with all other sources.

Using an external clock would have nothing to do with improving the synch performance of the TV set as it relates to the accuracy and stability of the DAC’s timing or that of other dCS products connected to it. The synchronisation " window" for locking with other equipment would remain the same.

Pete is correct. For an external clock to have an impact on a source device, that source needs to have a Word Clock input so that the source and DAC can be locked to the same clock.

As the TV does not have a clock input, there’s no way for us to get it’s clocking within range. As such, adding an external clock to the system wouldn’t resolve this issue.