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Does Quality of Coax Input Matter for DACs?

audio2design

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This is a forum that fetishizes over-designing. I wouldn't call doing the right thing over-designing either.

I see little evidence of that. We regularly point out that things are well beyond the limits of audibility. We appreciate good engineering. If it is the right thing it is not over designing. If you are providing something of no value, then it is not right, it is over designing. Sometimes we over design things to speed time to market. Providing excessive specs is also a marketing advantage so has value.
 

audio2design

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Don't bother, he's stuck in 1995 with Cirrus and Yamaha receiver ICs.

If you are going to be an ass (again), then you may want to follow the thread where I both gave an example and provided an extensive discussion of the way, and linked in other experienced designers showing the same thing.
 

chris719

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The spurs are at <20KHz. RF would both have to be at a high enough level, find a sensitive node that is not shunted for high frequencies (and sensitive to them), and normally have an AM modulation component at audio frequencies in order to impact the audio band. Periodic transmissions can do that, but spread spectrum greatly decreasing impact and that is pretty much standard for almost everything of any RF power today in a home. Turntable inputs can be sensitive to very close AM radio transmissions because they are high impedance but we are talking DACs.

You've never seen any weird stuff in spectra when we are talking about these extremely low levels? Come on.

Spread spectrum is of limited benefit in my experience. It obviously helps you pass testing because of the quasi-peak detection often used, but a noisy clock or DC-DC converter is still going to be noisy even if you make it wander.
 

chris719

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If you are going to be an ass (again), then you may want to follow the thread where I both gave an example and provided an extensive discussion of the way, and linked in other experienced designers showing the same thing.

I read your post, it's not really relevant with modern parts, which is why you can't find an example of this in a product Amir has reviewed.

Amazing really that you think I'm nuts for insisting you bond a shield to chassis at both ends as is best practice, but want to have a deep dive about a non-issue. Jocko (RIP) is that you?

Please, find me an example of a modern DAC that has its performance degraded to <16 bit due to jitter from poor termination / impedance mismatch. You can't even build one if you tried with a TI or AKM receiver I bet. Even without a CS2100 series device or ASRC after it. I'm sure you can build an interface that doesn't lock, but I'd like to see this degradation at the analog output.
 
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audio2design

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You've never seen any weird stuff in spectra when we are talking about these extremely low levels? Come on.

Spread spectrum is of limited benefit in my experience. It obviously helps you pass testing because of the quasi-peak detection often used, but a noisy clock or DC-DC converter is still going to be noisy even if you make it wander.

Follow the conversation. This was about EMI through a coax with transformer isolation. It was not about DC-DC, which as addressed, that transformer is sufficient for common mode rejection at the frequencies needed.
 

chris719

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Follow the conversation. This was about EMI through a coax with transformer isolation. It was not about DC-DC, which as addressed, that transformer is sufficient for common mode rejection at the frequencies needed.

Have you ever used an LME49710? Sometimes reality has a way of surprising you.

Speaking of follow the conversation, the whole point of my initial post was that optical is unfairly maligned. I guess you're allowed to go on about a minor related concern but not anyone else.

Still waiting for that <16 bit resolution jitter example. Unlike you, I made no claims about a little RF ingress affecting the audio band performance in general. Maybe I'm an ass, but if so, I'm not the only one here.
 

audio2design

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I read your post, it's not really relevant with modern parts, which is why you can't find an example of this in a product Amir has reviewed.

Amazing really that you think I'm nuts for insisting you bond a shield to chassis at both ends as is best practice, but want to have a deep dive about a non-issue. Jocko (RIP) is that you?

Please, find me an example of a modern DAC that has its performance degraded to <16 bit due to jitter from poor termination / impedance mismatch. You can't even build one if you tried with a TI or AKM receiver I bet. Even without a CS2100 series device or ASRC after it. I'm sure you can build an interface that doesn't lock, but I'd like to see this degradation at the analog output.

Do you even know what the PLL cut frequency is of those parts? News to @chris719, it is not the TI, or AKM or Cirrus PLL that gets rid of low frequency jitter, it is the ASRC, or pulse output DAC, etc. that does (or the odd one with a buffer). If you were less interested in trolling and looking smart and not calling others naive, you would go back up to where I clearly said that most modern DACs would not have an issue at all, and even the ones that do, it probably is not audible.

Amir just tested the MHDT Pagoda and low and behold, jitter components apparently < 16 bits. This is a modern, just released DAC. It is poorly designed, but it is what it is. Ditto the not that distant Schitt Modi2, Note that I never said a modern properly designed DAC would have an issue, but not everyone owns a competent DAC and that conversation that you are pedantically trolling was w.r.t. whether a cable poorly terminated could make a difference. It could with DACs that people are buying today and that they already own. That is just you being wrong in a poorly attempted troll. And with that, I will mute you as you bring absolutely nothing to the conversation.

audio2design said:

While the edge speeds in SPDIF are slow, which some may conflate with relaxed requirements for impedance matching, the voltage levels and hysteresis are also low, which does present the potential for jitter, which is not theoretical, but has been illustrated. If you have a new competent DAC, it probably does not matter, and given the limits of human hearing, in most cases it would not matter anyway, but there is still the potential for additional jitter with poor termination and the end result with some DACs will be < 16 bit performance.

1641842119020.png



Oh look an EMOTIVA 200 -- only 5 years old. Nasty:

1641847541586.png
 
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chris719

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Do you even know what the PLL cut frequency is of those parts? News to @chris719, it is not the TI, or AKM or Cirrus PLL that gets rid of low frequency jitter, it is the ASRC, or pulse output DAC, etc. that does (or the odd one with a buffer). If you were less interested in trolling and looking smart and not calling others naive, you would go back up to where I clearly said that most modern DACs would not have an issue at all, and even the ones that do, it probably is not audible.

Amir just tested the MHDT Pagoda and low and behold, jitter components apparently < 16 bits. This is a modern, just released DAC. It is poorly designed, but it is what it is. Ditto the not that distant Schitt Modi2, Note that I never said a modern properly designed DAC would have an issue, but not everyone owns a competent DAC and that conversation that you are pedantically trolling was w.r.t. whether a cable poorly terminated could make a difference. It could with DACs that people are buying today and that they already own. That is just you being wrong in a poorly attempted troll. And with that, I will mute you as you bring absolutely nothing to the conversation.



View attachment 178000


That's in the J-Test signal output. Which is not what you claimed. You claimed degrading the performance of the converter to < 16 bits, you did not specify "spurs in J-Test > 16-bits down". Nor did you say "jitter performance" explicitly in that post. When you talk about the performance of the converter, it would be automatically assumed by anyone experienced in data converters that you mean ENOB or SNR/DNR. This J-Test result does not mean the converter's resolution is below 16 bits. You also have to find a broken product to make this point... not only that, the example you dig up is of a USB interface.

Do you think you're the only person who knows how a PLL works?

Surely, if anyone is trolling here it is you. I'm not the one that's implying using 50 ohm coax instead of 75 ohm will cause horrific levels of jitter to scare people.
 
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Tangband

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That's in the J-Test signal output. Which is not what you claimed. You claimed degrading the performance of the converter to < 16 bits, you did not specify "spurs in J-Test > 16-bits down". Nor did you say "jitter performance" explicitly in that post. When you talk about the performance of the converter, it would be automatically assumed by anyone experienced in data converters that you mean ENOB or SNR/DNR. This J-Test result does not mean the converter's resolution is below 16 bits. You also have to find a broken product to make this point... not only that, the example you dig up is of a USB interface.

Do you think you're the only person who knows how a PLL works?

Surely, if anyone is trolling here it is you. I'm not the one that's implying using 50 ohm coax instead of 75 ohm will cause horrific levels of jitter to scare people.
An ASRC can ”froze” the incoming jitter, making it permanent if not careful - the measurements will then look fantastic but the sound will suffer if that happens, so its not always a good thing. An ASRC can also bring better sound with less jitter if done right.
 

chris719

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An ASRC can ”froze” the incoming jitter, making it permanent if not careful - the measurements will then look fantastic but the sound will suffer if that happens, so its not always a good thing. An ASRC can also bring better sound with less jitter if done right.

I understand what you're trying to say about how an ASRC converts error in one domain to another, but I don't think I have seen any evidence that this is audible in good implementations such as AD1896 and later. I've never seen one shred of evidence supporting this, but would be interested if you have any.
 

tonycollinet

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Come on guys - if you can't prove-someone-on-the-internet-wrong nicely, don't prove-someone-on-the-internet-wrong at all.

:cool:
 
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tpaxadpom

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I always heard that "TOSLINK has more jitter, avoid if you can" as audiophile wisdom, wonder how true it was/is. Might be interesting to apply a bit of myth busting to that. If it's easy for Amirm to do, and he thinks it's worth his limited time, of course. (Easy for us to come up w things to load on his table!)

Another note on TOSLINK, way back when I built a Twisted Pear Buffalo 1 DAC (DIY kit, one of the first ESS chip implementations) there was a type of TOSLINK adapter that would do 192khz audio they would try to supply, most were only able to sync to 96khz. The faster ones were going out of production?

Point being, your TOSLINK may vary, both in capabilities and quality. Also all the circuitry is inside the socket, photodetector to translating chip are molded into the connector body, at least in this style. No variations for product designers to mess with.
This is true and quite easy to measure the difference using various sources or AP built in generator. Not only Toslink is higher (~5 to 7X) but with AP I was also able to measure difference among different Toslink cables (and no glass Toslink wasn't the best for those that are curious). Even directionality was noted in some cases (likely caused by optical coupling differences). If one wants to experiment how the system would sound if the source was more jittery simply pull the Toslink cable slightly out of the jack. Enough to keep the PLL locked but cable must be loose at this point. Do you hear a difference? I compared jitter on about 5 AP 2722s (calibration up to date) using built in generator and external source - they all had different jitter readings (10-20% spread).
 

Blew

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Ripping your collection is a tedious, time consuming, job. But when you're done. You could (should) move the resulting files to a NAS/File Server/Cloud and stream it from there. You could also use Roon of course but this will cost you $12,99 a month. Roon is an excellent way to order your music and listen to streaming services. I refuse to use it because and I quote "Roon and MQA (Master Quality Authenticated) technology are firm friends" I'm not. Welcome to the wonderful world of capitalism.
Is that your only reason? That seems like cutting of your nose to spite your face. Roon is great for many things, but I decided not to use it because of other reasons, mostly the cost and lack of support for DLNA devices. MQA is just another codec that it supports and includes a license for, much like DSD, AAC, and MP3 (pre 2017).
I already painstakingly tagged everything myself. FLAC was released on July 20, 2001 and I didn't have access to all those sophisticated online databases like FreeDb (unfortunately defunct ) yet and I had to "tag" everything by myself. Nowadays you could use something like the extensive database of Discogs.
Musicbrainz Picard is your friend. Free and open source in both software and database (unlike CDDB was):
 
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