Bartok and Rossini dac problem using optical connection

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.

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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.

@Givara, based on James’ explanation of the issue, what you might want to try is an active TOSLink Repeater or Splitter; one that will regenerate your LG TV’s TOSLink signal, in the hopes that the regenerated signal is well within proper specs.

Something like this between your TV and your dCS;

There’re quite a few on Amazon. Make sure it’s an active unit, meaning it requires power, and not one of the passive optical splitters. Shouldn’t cost more than a couple of cups of Starbucks, so no real harm if it doesn’t work :crossed_fingers:t3: :grin:

Anup, that is such a creative suggestion. I really hope that it works for Givara and that adm95 who has the same difficulty with his LG TV gets to see your post.

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Whether or not this sort of device works will depend on if the repeater is reclocking the signal or simply “squaring” it.

Reclocking it, as the Oppo player seems to do, means that it is using a clock with a wider pull range and playing back the audio samples based on its own internal clock. This would make the samples more in time and mean the dCS unit would be able to lock to it. You’ll get some audio artefacts in the signal (dropped samples) but it will play back.

If the device is simply using a squaring circuit, it won’t be changing the timing of the signal, simply making sure that the optical equivalent of the output voltages are correct. It allows signals to be transmitted over larger distances. As it won’t be changing the timings of the signal at all, it won’t have an impact on the dCS unit being able to lock to the signal.

I’ve seen devices do both, so I couldn’t make any guarantees on whether one would work or not!

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All toslink spletters and repeaters that i found on internet do not have own clock

can u plz suggest a model that have a clock in it? only in Moscow i know 3-4 ppl having problems with DCS-LG and that could realy help us. OLED Lg tvs are so popular that this will not be such a rare problem for DCS customers

These two claim to reclock TOSLink inputs and might fit the bill. I have no personal experience with either, and not quite as low-cost as the Amazon units, but these might actually work I suppose. :crossed_fingers:t3:

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What superb suggestions @Anupc! This has inspired me to stage an experiment this weekend. I have an LG OLED monitor which is is now connected over HDMI to a Marantz pre/pro. The Marantz also hosts an Oppo 205, and the 4K boxes by Apple, Amazon, and Roku. This all feeds a 7-channel amp and separate in-wall speakers for home theater. The Oppo is also connected to the Vivaldi DAC via Toslink (for the occasional disc playback). I tested the sound in this configuration before I installed the clocks, and it seemed to work fine.

But now I want to try and see what happens when I simply run optical out of the LG into the Vivaldi, and what happens if I run optical out of the Marantz into the Vivaldi.

Imagine if it actually works without a problem, and then what? :rofl:

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would love to hear your outcome!

A brief explanation for my delay. I could not get Vivaldi DAC to lock on to the Toslink signal from the LG, but I cannot verify that is my actual outcome yet. I believe something about the HDMI path between the Oppo, the Marantz, and the LG was complicating the assessment. So, this weekend, I will remove the Oppo and Marantz from HDMI path altogether, connect an AppleTV to the LG directly via HDMI and see what I can hear.

I can now confirm my Vivaldi DAC locks on to the optical output from my LG TV (model 77EG9700-UA) with no problem (except that video and audio are not in sync, and there is insufficient flexibility in either the LG’s or AppleTV’s settings to correct it). Vivaldi screenshot below. image

So Greg, where does that leave us?

I think that it might indicate that the locking problem may lie not with the LG brand per se but with the 65C8 which is what I think both of the originators in this thread have.

Unfortunately even this information may be of little help. This is due to the fact that the large far eastern TV manufacturers do not necessarily make identical TVs for different markets even if they carry the same model number.

That still leaves you with the latency problem causing a lack of synch between video and audio. I vaguely recall seeing some black boxes that were supposed to deal with this issue years ago when reading some specialist Home Theatre mags. Haven’t seen one for years though so I have no idea if such things are still available.

I have a similar recollection Pete. I took a quick look, and could not find any though. The LG TV does have a sync adjustment, but it’s insufficient to get the audio in sync. It’s interesting that, in most home theater articles, the problem appears to be that the video lags the audio. [It’s also interesting that Toslink seemed to top the list of problem conduits.] My experience was that the audio severely lagged the video, by as much as a half second.

For me, this is not really a problem, because I prefer to run the TV separately through the pre/pro and the HT amps and in wall speakers. It’s nice to be able to play the Oppo through Toslink into the Vivaldi DAC for occasional disc playback, and that doesn’t require sync. But for folks who need this to work in order to integrate their video into their lovely dCS system, I am afraid I do not have a solution.

Should be “A” in the clock selection, whrn “M” selected oudio dropouts can happen every 20-40 mins in “A” dropouts happene every several minutes

Greg, was the TOSLink directly into your DAC or to the Upsampler? Did you try Clone-Mode (Upsampler) and Buffers Off (DAC)? That should minimise delays.

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