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What’s special about ‘digital coax’?

BitPerfect_

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This is the answer that I’ve been looking for. I thought that using a dedicated coax cable (75 ohms) the sound will de different compared with an audio RCA cable in the same price range and the same brand (to eliminates other variables).

No, there is no dropout or popping, I’ll keep the existing cable.

Thank you for sharing this valuable information.
 

BitPerfect_

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@SIY , in your opinion the same thing will apply to toslink optical cables?
I just found that some of them could handle up to 32 bit/ 384 kHz at least on the paper. Marketing stuff or here the bandwidth-thing is true?
If we’re talking again about 0 and 1, I’m not sure how to use this information.

Thanks,
 

symphara

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@SIY , in your opinion the same thing will apply to toslink optical cables?
I just found that some of them could handle up to 32 bit/ 384 kHz at least on the paper. Marketing stuff or here the bandwidth-thing is true?
If we’re talking again about 0 and 1, I’m not sure how to use this information.

Thanks,
If I remember correctly toslink was designed for maximum 24/96. Even if you could send more on the media, I don't know of any audio device that will do so.
 

BitPerfect_

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Both devices in my case, the streamer (page 46 of 48) and the amp (the first page) supports 24/192 via Optical and Coax, that’s why I’m asking.
 
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symphara

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Both devices in my case, the streamer (page 46 of 48) and the amp (the first page) supports 24/192 via Optical and Coax, that’s why I’m asking.
Did you try 24/192 on toslink and it worked? On a Yamaha WXC-50? Very impressive.
 

audio2design

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This is the answer that I’ve been looking for. I thought that using a dedicated coax cable (75 ohms) the sound will de different compared with an audio RCA cable in the same price range and the same brand (to eliminates other variables).

No, there is no dropout or popping, I’ll keep the existing cable.

Thank you for sharing this valuable information.

The issue, not sure I saw in the comments, is that RCA connectors are rarely a true 75 ohm connection, and that applies for both the connector on the cable and the connector on both pieces of equipment.

If you have an impedance mismatch, you get reflections, and depending on the length of the cable and the electronics on each end, and to some degree the cable, those reflections can happen just at the right time to create pretty bad jitter.

Often, simply changing the cable length to <0.75M, or >2.0m, will eliminate the issue. However, as you found, just changing the cable fixed it.
 

radix

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@SIY , in your opinion the same thing will apply to toslink optical cables?
I just found that some of them could handle up to 32 bit/ 384 kHz at least on the paper. Marketing stuff or here the bandwidth-thing is true?
If we’re talking again about 0 and 1, I’m not sure how to use this information.

Thanks,

As long as your devices are rated at 192k over TOSLINK, you're ok. I've not seen any 384k TOSLINK, but that doesn't mean it does not exist.

AES/SPDIF/TOSLINK are all 24-bit maximum sample sizes. That's what the data frame is (really it's 20-bit but there's 4 extra bits one can use). I am not sure how 32-bit works over the protocol....

Ok, I looked it up. In IEC 60958-5 2021-02 (Digital Audio Interface - Part 5: Consumer application enhancement), there are extensions for a 32-bit and a 64-bit samples. Basically, they only send 16 bits per 32-bit subframe, and concatenate 2 or 4 frames for 32-bit and 64-bit samples. So, you have to run at 2x or 4x the clock rate.

So, 384 kHz sample rate takes 128 bits of framing for 2 channels at 32 bits, so the clock rate is 2 x 384000 x 128 = 98.304 MHz clock rate. I am not sure how copper would do for that, but it's still peanuts for optical. As long as each end says it supports it, it should work with a standard TOSLINK cable (I am guessing).

My question is why?

I cannot imagine any audible reason to use 384 kHz @ 32-bit.

Marc
 

BitPerfect_

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Did you try 24/192 on toslink and it worked? On a Yamaha WXC-50? Very impressive.
Unfortunately I can’t read the output sample and the bit depth because I don’t have a dac with display but according to the technical sheets it could output.

LE: you're right @symphara , there is a limitation. I just read that in Pre Amp mode, the WXC will down-sample to 48 kHz. On the other hand, in Player mode, there is no sample rate conversion going on inside the Yamaha, the unit will output via toslink or spdif, following the sampling rate of the input. The problem is that the signal is delivered at maximum volume without the possibility to adjust it.

Thank you all
 
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BitPerfect_

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My question is why?

I cannot imagine any audible reason to use 384 kHz @ 32-bit.
Indeed, I just wanted to be sure that even if the devices (emitter/ receiver) supports 24/192 the cable will not reduce these values. Choosing a cable with that max bandwidth will cover 24/192 for sure. On the other hand, between a Coax and a Toslink cable, in these conditions, knowing that the 24/96 was applied for old protocols , I’ll choose Toslink in order to avoid any possible interference for example with the power supply cable which is near.

The question is, how an optical cable could carry more or less amount of data it’s about the fibre optic material? We are not talking about glass fibre optic here.

Not being able to measure, if I purchase a regular toslink cable and there are no pops and clicks or interruption it means that will properly transfer the rated amount of data sent by the emitter?
 
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amirm

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Every time I test an AV product, I run into whether Coax or Toslink go above 192 kHz. In many cases neither does. In some, Coax will go to 192 but Toslink will not.
 

BitPerfect_

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Hmm ..so it’s not actually it works or not, 0 or 1, it could still work without interruptions but at a lower value (coax or toslink). Good to know, thanks.
 

Dumdum

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Tbh my coax is 4m long in my car, I buy van damme 75ohm coax cable for under a tenner for 5m and rean Rca plugs, I’ve never run into any issues with transmission

The only time I’ve ran into issues with digital transmission is with optical when Amazon hd was forcing the maximum bitrate the topping d10s would do because it’s stupid and the optical cable wouldn’t transmit, I only worked it out when I connected my pc to the topping and forced a lower resolution
 

Kijanki

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Indeed, I just wanted to be sure that even if the devices (emitter/ receiver) supports 24/192 the cable will not reduce these values. Choosing a cable with that max bandwidth will cover 24/192 for sure. On the other hand, between a Coax and a Toslink cable, in these conditions, knowing that the 24/96 was applied for old protocols , I’ll choose Toslink in order to avoid any possible interference for example with the power supply cable which is near.

The question is, how an optical cable could carry more or less amount of data it’s about the fibre optic material? We are not talking about glass fibre optic here.

Not being able to measure, if I purchase a regular toslink cable and there are no pops and clicks or interruption it means that will properly transfer the rated amount of data sent by the emitter?
Toslink transmitters are many times slower than coax drivers. System electrical noise, will add to edge (modulating light) at transmitter end or/and will modulate threshold point at the receiving end - causing variation in time (jitter) of received words (slower edge will be modulated more). If we send digital words representing 1kHz sinewave when time of delivery is slightly modulated with, for instant 60Hz, it will get converted to 1kHz sinewave and sidebands spaced 60Hz apart. Only first two at 940Hz and 1060Hz will have audible levels. Amplitude of these sidebands will be proportional to amplitude of time variation, being usually below -65dB, but still audible because they are not harmonically related to root frequency (like harmonic distortions are). With a lot of frequencies (music), there will be a lot of sidebands - basically a noise (that is non-audible without signal). So, with Toslink I would keep system electrical noise to minimum (power conditioner etc.)

Coax has different problem. Fast transitions reflect in the cable on impedance boundaries. Signal in typical CDPs swings in about 25ns. Taking 1.5m cable and 5ns/m propagation reflection from the end of the cable will come back in 2 x 1.5m x 5ns = 15ns after "knee" starting transition, just missing half of transition (12.5ns) where most likely threshold lies, without modifying transition shape, that leads to jitter (modifying it after level is recognized) . Using cables longer than 1.5m, possibly 2m is advised. Of course transition times can vary and can be much shorter with dedicated transports. Another option is to use very short cable. Rules of the thumb (for time domain) says that cable becomes transmission line (reflections) when propagation time one way is longer than 1/8 of transition time. For 25ns it is about 4ns making it 0.8m cable. I would not make it longer than a foot, because connections inside of the gear on both ends also count. The best would be as short as possible. I used once 6" coax with good results. With Benchmark DAC3 now I use glass Toslink for practicality (no ground loops or electrical noise pickup). DAC3 has very strong jitter rejection (Asynchronous Rate Converter).
 

Beave

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Toslink transmitters are many times slower than coax drivers. System electrical noise, will add to edge (modulating light) at transmitter end or/and will modulate threshold point at the receiving end - causing variation in time (jitter) of received words (slower edge will be modulated more). If we send digital words representing 1kHz sinewave when time of delivery is slightly modulated with, for instant 60Hz, it will get converted to 1kHz sinewave and sidebands spaced 60Hz apart. Only first two at 940Hz and 1060Hz will have audible levels. Amplitude of these sidebands will be proportional to amplitude of time variation, being usually below -65dB, but still audible because they are not harmonically related to root frequency (like harmonic distortions are). With a lot of frequencies (music), there will be a lot of sidebands - basically a noise (that is non-audible without signal). So, with Toslink I would keep system electrical noise to minimum (power conditioner etc.)

Coax has different problem. Fast transitions reflect in the cable on impedance boundaries. Signal in typical CDPs swings in about 25ns. Taking 1.5m cable and 5ns/m propagation reflection from the end of the cable will come back in 2 x 1.5m x 5ns = 15ns after "knee" starting transition, just missing half of transition (12.5ns) where most likely threshold lies, without modifying transition shape, that leads to jitter (modifying it after level is recognized) . Using cables longer than 1.5m, possibly 2m is advised. Of course transition times can vary and can be much shorter with dedicated transports. Another option is to use very short cable. Rules of the thumb (for time domain) says that cable becomes transmission line (reflections) when propagation time one way is longer than 1/8 of transition time. For 25ns it is about 4ns making it 0.8m cable. I would not make it longer than a foot, because connections inside of the gear on both ends also count. The best would be as short as possible. I used once 6" coax with good results. With Benchmark DAC3 now I use glass Toslink for practicality (no ground loops or electrical noise pickup). DAC3 has very strong jitter rejection (Asynchronous Rate Converter).

It's a good thing none of that makes any audible difference whatsoever.
 

BitPerfect_

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@Kijanki Thank you for your feedback. I have to recognise that there are technical details not so easy for me to be fully processed.

On the other hand, I ended up purchasing and testing 3 regular cheap Toslink cables (Techlink Wires1st, Ugreen, Vention) different lengths up to 2m and the Dac receive without problems 24/192. No unwanted sounds at Streamer’s power On/Off (which I’ve experienced with Coax), no pops and clicks, the stream of data is continuous the Dac/Streamer are isolated, no ground loops.

If there is an audible jitter - I have no idea but compared with coax, from my perspective there is no difference but I solved any possible interferences or ground loops issues.
 
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Blumlein 88

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Toslink transmitters are many times slower than coax drivers. System electrical noise, will add to edge (modulating light) at transmitter end or/and will modulate threshold point at the receiving end - causing variation in time (jitter) of received words (slower edge will be modulated more). If we send digital words representing 1kHz sinewave when time of delivery is slightly modulated with, for instant 60Hz, it will get converted to 1kHz sinewave and sidebands spaced 60Hz apart. Only first two at 940Hz and 1060Hz will have audible levels. Amplitude of these sidebands will be proportional to amplitude of time variation, being usually below -65dB, but still audible because they are not harmonically related to root frequency (like harmonic distortions are). With a lot of frequencies (music), there will be a lot of sidebands - basically a noise (that is non-audible without signal). So, with Toslink I would keep system electrical noise to minimum (power conditioner etc.)

Coax has different problem. Fast transitions reflect in the cable on impedance boundaries. Signal in typical CDPs swings in about 25ns. Taking 1.5m cable and 5ns/m propagation reflection from the end of the cable will come back in 2 x 1.5m x 5ns = 15ns after "knee" starting transition, just missing half of transition (12.5ns) where most likely threshold lies, without modifying transition shape, that leads to jitter (modifying it after level is recognized) . Using cables longer than 1.5m, possibly 2m is advised. Of course transition times can vary and can be much shorter with dedicated transports. Another option is to use very short cable. Rules of the thumb (for time domain) says that cable becomes transmission line (reflections) when propagation time one way is longer than 1/8 of transition time. For 25ns it is about 4ns making it 0.8m cable. I would not make it longer than a foot, because connections inside of the gear on both ends also count. The best would be as short as possible. I used once 6" coax with good results. With Benchmark DAC3 now I use glass Toslink for practicality (no ground loops or electrical noise pickup). DAC3 has very strong jitter rejection (Asynchronous Rate Converter).
Has anyone measured the things you describe as changing the output of the DAC? I think the effects you describe are all so low as to be something we can ignore.
 

Kijanki

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@Kijanki Thank you for your feedback. I have to recognise that there are technical details not so easy for me to be fully processed.

On the other hand, I ended up purchasing and testing 3 regular cheap Toslink cables (Techlink Wires1st, Ugreen, Vention) different lengths up to 2m and the Dac receive without problems 24/192. No unwanted sounds at Streamer’s power On/Off (which I’ve experienced with Coax), no pops and clicks, the stream of data is continuous the Dac/Streamer are isolated, no ground loops.

If there is an audible jitter - I have no idea but compared with coax, from my perspective there is no difference but I solved any possible interferences or ground loops issues.
Great. The thing to look for is clarity, since jitter is adding noise. Pops or clicks would be extreme. It would have to be really bad Toslink connector or completely mismatched coax.
 

BitPerfect_

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Oh, good to know, thanks. I thought that having a continuous stream, as long as the signal is digital 0/1 will be always as the source will deliver, not a question of clarity.

In this case, only a measurement test will tell how ‘clear’ is the sound, comparing a Coax with a Toslink.
 

JustJones

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Hi All,

I have a simple question. I am remodeling a house and having a new cable run throughout while the walls are open. I have never bought a Coax cable. I assume I need RG6, but can anyone make a recommendation on a brand or a site to buy from? I will be using Comcast Xfinity X1 for cable tv.
I've bought from Here as well as local at Lowes or home depot. Can't go wrong sticking with Belden.
 
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