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Mythbusting

109.47.246.70

Posted on August 20, 2011 at 11:01:28
Ole Lund Christensen
Manufacturer

Posts: 1878
Location: Denmark
Joined: January 1, 2001
a lot of people claim the digital signals are just one and zero, so cables and connectors do not matter.

I assume that all in AA know that it is more complicated than that?

 

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RE: Mythbusting, posted on August 20, 2011 at 13:43:18
audioengr
Manufacturer

Posts: 6017
Location: Oregon
Joined: April 12, 2001
Some of us know. It's ones and zeros and jitter.

In some cases it's possibly floating-point math and CODEC errors in the software.

 

RE: Mythbusting, posted on August 20, 2011 at 20:08:22
Dawnrazor
Audiophile

Posts: 12044
Location: N. California
Joined: April 9, 2004
Hey OLC,

Most do know, but a couple here could use some info. Dont want to name names but they are here.

Though you would be best off posting this at Hydrogenaudio.org.

I bet it wouldnt take you too long to be banned...

Cut to razor sounding violins

 

RE: Mythbusting, posted on August 20, 2011 at 21:11:38
Scrith
Audiophile

Posts: 1169
Location: Los Angeles
Joined: July 19, 2005
It is 1's and 0's, actually. That's why we can download digital music off the internet (which is fully of all kinds of dubious connectors and cables, I assure you) and it all sounds the same (as long as the checksums are right, I suppose).

However, there are some digital systems that have a dependency on jitter between the transport and the DAC. And there are those who would argue (with zero scientific evidence) that cables and connectors make a difference. My own opinion is that I'm not sure, so I've got some pretty expensive cables in my system. Do i hear a difference between an expensive cable and the cheap cable is replaced? Of course I do. Is that just my imagination based on how much I want to like my shiny, new, expensive cable? Probably.

 

So tell us what digital data is then if not binary ones and zero's, posted on August 20, 2011 at 21:27:40
Tweekeng
Audiophile

Posts: 2093
Joined: September 9, 2005
Please elaborate.

 

RE: Mythbusting-zero science?, posted on August 21, 2011 at 00:09:43
fmak
Audiophile

Posts: 12977
Joined: June 1, 2002
Read up on the science underpinning interfaces, signal transmission integrity etc.

 

RE: Mythbusting, posted on August 21, 2011 at 05:11:28
Tony Lauck
Audiophile

Posts: 13629
Location: Vermont
Joined: November 12, 2007
"However, there are some digital systems that have a dependency on jitter between the transport and the DAC."

Not "some". Certainly "most". Perhaps "all".

Also, these are not "digital systems". They are "mixed signal" systems.

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar

 

Word clock, posted on August 21, 2011 at 06:38:02
Ole Lund Christensen
Manufacturer

Posts: 1878
Location: Denmark
Joined: January 1, 2001
Let us assume that your bank account on Wednesday has $65,535 .That is written somewhere in the bank computer as $1111111111111111, the largest possible 16 bit number.

Thursday you buy the big Hi-Fi system of your dreams, and you have $0000000000000001 left.

So in that weekend you buy a $1 dinner :-)

But Monday the yearly bonus arrives to your bank account and you have $1111111111111111 again.

Replace the $ with sound levels, and you have some big transients, from maximum to almost silent and back to maximum.

Now if the bonus came on Friday, you could invite all your friends to a weekend dinner.

Clearly the arrival date of the bonus is important for your weekend dinner.

Replace again $ with sound levels, and you see that the arrival time of the big sound level of 1111111111111111 is important.

Where is the arrival time written? On your bank account it is written beside the $ amount, like this 2/28/2011 $65,535

In the S/PDIF digital audio signal, we only have one line, so all data have to be sent serial, not parralel. Plus we have a lot of extra bits giving space for stereo 24 bit audio as well as instructions and clock.

That means the signal is not anymore 44,1 kHz but several Mega Hertz. At such a frequency cables behave like transmssionlines, and impedances of cable and connectors have to match to avoid reflections (signals going in the wrong direction) Depending on the high frequency performance of the cable, it becomes difficult for the receiver IC to know, when the voltage is 0 and when it changed to 1, because it now change at a slow slope, and no longer makes a sharp change. The arrival time code is mixed in as a part of the signal and it becomes uncertain too. A lot of work have been done on reducing this problem in receiver ICs, but it just reduced, not solved.

So S/PDIF cables have to have the correct impedance, not just low capacitance and low inductance. To make life easier for the receiver IC. You can read more about S/PDIF in Wikipedia.

All this is well known in analog TV, because here the reflections are seen as ghost lines in the analog picture.

There is a much better way of sending digital audio, and it is used inside most CD players. It is called I2S and it uses 3 lines instead of just 1.

see link

 

thank you, I took at look around Hydrogen Audio, posted on August 21, 2011 at 09:05:47
Ole Lund Christensen
Manufacturer

Posts: 1878
Location: Denmark
Joined: January 1, 2001
they seem like nice chaps, just lacking some fundamental education in science.

But I found this poor hardworking developer writing:

"I know, I know. It's not a good idea. :-)
However, I am working at an audio encoder and I can't test hundreds of files for every minimal change I make.
And besides that, I am partially deaf, so it would be pointless anyway.
Any suggestion on some software that can help a bit? Open source/publicly available obviously preferred.
Thanks"

No comments needed from me.

 

I2S, posted on August 22, 2011 at 10:35:55
audioengr
Manufacturer

Posts: 6017
Location: Oregon
Joined: April 12, 2001
Some of use use I2S externally too, with good results. Like S/PDIF though, the devil is in the detials. The Transmission-lines must be terminated and the edge-rates must be fast in order to avoid adding significant jitter. Really low-loss high-bandwidth cables are required.

 

RE: Word clock, posted on August 22, 2011 at 21:36:44
Dawnrazor
Audiophile

Posts: 12044
Location: N. California
Joined: April 9, 2004
Hey Ole,

I thought i2s was one of the advantages pci cards.

Cut to razor sounding violins

 

RE: I2S, posted on August 23, 2011 at 09:24:54
Tony Lauck
Audiophile

Posts: 13629
Location: Vermont
Joined: November 12, 2007
Do you know of any systems that run I2S where the clock goes in the reverse direction from the data?

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar

 

possibly the "enhanced" version, posted on August 23, 2011 at 18:10:00
Joe Murphy Jr
Audiophile

Posts: 4424
Joined: February 3, 2001
The I2S-e interface is supposed to allow the DAC clock to control the data flow. Other than the Sonic Frontiers/Assemblage line and the Muse products that use it (the two systems are not compatible though), I don't think there are others. You can ask Charles Hansen -- though he hates any external implementation of I2S -- for a copy/link to the white papers, Chris Johnson at partsconnexion.com (he was the head of Sonic Frontiers/Assemblage) or Kevin Halverson at hrtechnologies.com (founder and chief engineer at Muse Electronics) for more info.

 

I have looked around in vain for I2S on PCI cards , posted on August 24, 2011 at 13:20:57
Ole Lund Christensen
Manufacturer

Posts: 1878
Location: Denmark
Joined: January 1, 2001
Did you think of I2C? This is a 2 wire computer standard, I2S is a 3 wire digital audio standard. They are based on the same ideas.

see link

 

RE: I have looked around in vain for I2S on PCI cards , posted on August 25, 2011 at 00:25:38
Dawnrazor
Audiophile

Posts: 12044
Location: N. California
Joined: April 9, 2004
Hi Ole,

Forgive me for being confusing. Let me explain.

I was thinking i2s. I probably have this wrong but I remember charles Hansen talking about the phillips sony guys needing to do some measurments or such and the i2s protocol was born...it was not envisioned as a connection between boxes IIRC.

I thought that all cdps had this connection internally to the dac chip. I took your post to mean that this was better than spdif and that to me at least made sense that a short connection to the dac chip would be better than a long cable connection. I had thought that by default a soundcard using its own dacs would have an i2s connection of sorts. Is that not right?

Though I think you took my post to mean external connection from a soundcard to an external dac. There was once a card that did that but the links are dead and this is the best I could find:

Cut to razor sounding violins

 

RE: Mythbusting, posted on August 25, 2011 at 10:15:35
magiccarpetride
Audiophile

Posts: 1458
Joined: March 31, 2010
"a lot of people claim the digital signals are just one and zero, so cables and connectors do not matter. I assume that all in AA know that it is more complicated than that?"

That would depend on what aspect of digital are we talking about. The issue with digital is that it can be viewed both as a blueprint and as a final product. Unlike in non-virtual world, where even the least educated person has no trouble distinguishing between a blueprint of a chair and a finished, physical chair one can sit on, in the world of digital that distinction is not that obvious to the uneducated.

When musical performance gets recorded, the information captured on tape can be converted to a digital blueprint. This digital blueprint can then serve as a recipe that will guide the machinery on how to produce the final product -- in this case, the final product would be the weak electrical current that will be fed into a DAC. However, the digital blueprint itself can never be listened to; it can only be regarded similar to how we regard a recipe -- i.e. a piece of paper sitting in a drawer, ready to be pulled out and used when preparing a meal. But one cannot satisfy one's hunger by eating that piece of paper.

In that regard, we see that indeed it all boils down to ones and zeros. This 'recipe', or music blueprint can be copied indefinitely and at will, and each subsequent copy is guaranteed to remain 100% identical to the original blueprint.

However, what is NOT guaranteed is that each time this recipe is used to prepare a meal, that each meal will taste identical to the previous meal made from the identical recipe. Or, if we stay with the blueprint analogy, two different shops can use the same blueprint to build a chair, but these chairs will NOT end up being identical.

In the above case, we see that it's not only about ones and zeros, and that the final product wildly varies depending on many other factors and conditions.

 

RE: Mythbusting, posted on August 25, 2011 at 12:08:00
Roseval
Audiophile

Posts: 1737
Joined: March 31, 2008
Management summary: if you play digital audio on different gear it will sound different.

Addendum: applies to non-digital media as well

The Well Tempered Computer

 

RE: Mythbusting, posted on August 25, 2011 at 12:44:59
magiccarpetride
Audiophile

Posts: 1458
Joined: March 31, 2010
"Management summary: if you play digital audio on different gear it will sound different."

Executive summary: if you play digital audio on the same gear where only digital transport is different, it will sound different.

 

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