digital experiment

[fixerfrasse]

I think that we are all talking about the same thing, only we might not understand each point of view.

Let's face it, digital signals is transfered in analog wires (well perhaps not in optical wires). But since digital data is coded into ONs and OFFs in these wires we need to code them using timescycles. To do that we use of high precision clocks that synchronises the sending and receiving chip, so that they work in the same speed. The clock, a particular wire or even a transmitting chip can introduce jitter in the pathway of digital data.

Now as long as the sending and the receiving chips is digital, a little jitter here or there is no problem because the chips generally understand each other anyway. If some chips become unsyncronised, and if something for this reason went horribly wrong somewhere, another layer ontop of the transport layer check the data and ask for a resend if it is corrupt.

However, a DAC chip is part digital and part analog. It stores up 24 bit (I am talking about a 24-bit DAC chip now, for the sake of simplicity) and when it got them all, it outputs the correct analog signal. So for a regular digital chip this doesn't matter because data arrives sooner or later anyway, and if somethings wrong, someone have the responsibility to check the validity and ask for a resend. But for the DAC chip it's critical that it steadily sums up and send out the correct analog signal. Therefore the digital stream that is sent to the DAC chip must be as jitterfree as possible.

There can be a number of reasons why the stream isn't jitter free when it ends up in the DAC. If the CD-player is stupid enough not to reclock the data properly before sending it to the DAC device, then ofcourse the quallity of the CD is important. But simple portable CD-players have shake protection memory and those would most certainly remove any jitter that might be written to the CD.

To sum up, jitter is a time phenomenon. In the digital world it can slow down data transferes, but in the end the data will turn up correct on the other side of the wire. When translated to analog signals this data stream must be very steady (jitter free). That means the digital pulses must come in as correct timing as they possibly can. So in a way, besides the analog out signal, the DAC chip works analogy internaly with time as the analog factor (strange centence).

However, there might be a second issue. If the digital pulses come correctly timed but with fluctuation of voltage or current, this might have an effect on the DAC chip aswell. But I'm not sure. I beleive that the DAC wait untill all 24 bit's have arrived, thus storing them. When it has them all, i think it utilises another power source to output the analog signal based on the value that the stored bit's sum up to. Could anyone shed some light on this? Fluctuation of this type might ofcourse affect the chip anyway.

[soundcheck]

Originally posted by fixerfrasse
ITo sum up, jitter is a time phenomenon. In the digital world it can slow down data transferes, but in the end the data will turn up correct on the other side of the wire.

VERY INTERESTING. Please define "correct on the other side" please!

------------------------------

Jitter accumulates over different stages on a realtime stream, if there is no stage involved being in charge to get rid of the jitter
as far as possible.
Take USB to SPDIF conversion just to give an example. Here are measurements clearly showing that the jitter almost doubles, when converting USB-SPDIF-I2S instead of doing it USB-I2S.
You'll hear that by the time the signal hits the DAC.


Regarding CD-Write Jitter:

You (glassmann) might want to read this.

http://www.cdrinfo.com/Sections/Revi...6513&PageId=12

Cheers

[Glassman]

Originally posted by soundcheck
Regarding CD-Write Jitter:

You (glassmann) might want to read this.

http://www.cdrinfo.com/Sections/Revi...6513&PageId=12

Cheers

sure, thats the pit/land jitter I've been talking about.. however you have to realise that the self-clocking of the CD track is only used for synchronisation and raw data demodulation from the RF signal comming from pickup - it is not the master clock used for D/A conversion! I suggest reading through a few CD chipset datasheets, you'll understand..

[fixerfrasse]

Originally posted by soundcheck


VERY INTERESTING. Please define "correct on the other side" please!

"Correct on the other side" as when you transfere something and the data is exactly the same on both sides of the wire.

[gabrielbecheanu]

Hi
I am glad. The subject seems to be interesting for the forum members but I think that it goes in the wrong directions.
Lets say that we have perfect rip,(for us the jitter is not important if we have 100% the same information as original). The result is 10 wav files , we process the data with a specialized program on a PC from 16bit 44.1kHz to 16bit 176.4 kHz after that we burn the result on a DVD R with another specialized program for DVD Audio. It is important to make a DVD Audio because the normal DVD Players can’t handle sample rates more than 96 kHz, only the DVD players that have DVD Audio futures can do this. So what do you think? Is the result better than a normal cd if we play on a budget DVD Audio player like Panasonic S52 or a low cost Pioneer? What to do? To pay 1000 euros or more for a decent cd player or process all the cd from our home to have a better sound on a decent audio setup.

A few weeks ago a guy sent me this link http://db.audioasylum.com/cgi/m.mpl?...ah&r=&session=

Anyone read this before?, any comments?
For most of us I think it’s important to have good sound quality in affordable stereo home system, not all the people have system that cost 30000 euros or more.

[Werner]

Originally posted by gabrielbecheanu

wav files , we process the data with a specialized program on a PC from 16bit 44.1kHz to 16bit 176.4 kHz after that we burn the result

Make it to 24 bit 176.4kHz, not 16b lest you lose accuracy of the filter results.

Originally posted by gabrielbecheanu

the result better than a normal cd if we play on a budget DVD Audio player like Panasonic S52 or a low cost Pioneer?

The only difference would be in the quality of the player's inbuilt reconstruction filter versus that of the off-line software filter. Either one can be better, although the software version stands more chance of factually being better.

Then it remains to be seen if this is audible.

What does not chance at all is the suspect quality of the budget player's DAC chip, power supply, and analogue output stages.
And that's where a lot of the sound gets lost.

Originally posted by gabrielbecheanu

A few weeks ago a guy sent me this link http://db.audioasylum.com/cgi/m.mpl?...ah&r=&session=

A technical review in HFN by Keith Howard revealed that this program does some trickery to the signal that goes beyond mere high-quality sample rate conversion. This looked a lot like deliberately added distortion.
Again, some people may like it, some may not. Nothing wrong with that.

[gabrielbecheanu]

Originally posted by Werner

Make it to 24 bit 176.4kHz, not 16b lest you lose accuracy of the filter results..

Hi
Thanks for the advice.
I did some experiments also in 24 bit 176.4kHz.The software that i used for those experiments were : for ripping the cd : EAC, to resample the files : Wavelab5, for burning the result : Diskwelder chrome. Indeed, if you use a better DVD player the sound improves noticeably. For this test i also used a Denon DVD 3910 and AVR 4306.

Cheers

[Werner]

This site http://src.infinitewave.ca/ has comparative testing of various SRC programs.

[gabrielbecheanu]

Hi
Something interesting http://sound.westhost.com/cd-sacd-dvda.htm

[FastEddy]

Of interest: 16bit v. 24bit v. vinyl, merchandising and marketing confusion prevail :

Consider the Beatles music album "Love" produced by George Martin, a remix from the original masters with some very interesting revisions and compilations:

"Love - Standard Edition" = "standard" audio CD (1 disc)
http://www.amazon.com/Love-Standard-.../dp/B000JJSM4S

"Love - Special Edition" [EMI Import] = "standard" audio CD plus DVD-A version (2 discs)
http://www.amazon.com/Love-Special-B.../dp/B000JBXLOM

"Love - Special Edition" [Capital USA] = "standard" audio CD plus Audio DVD (2 discs)
http://www.amazon.com/gp/product/B000JJS8TM

"Love [Digipack With Bonus DVDA 5.1 Surround Sound - Apple Label!]" = standard CD plus DVDA (apparently with some video footage) (2 discs)
http://www.amazon.co.uk/Love-Digipac.../dp/B000JJS8TM

"Love" = "standard" CD (1 disc)
http://www.amazon.co.uk/Love-Beatles/dp/B000JK8OYU

"Love [Toshiba Import(?)]" = "standard" CD (1 disc)
http://www.amazon.co.uk/Love-Beatles/dp/B000JJSM4S

....
Typical Amazon review: " ... The mixing has, of course, been done on state of the art equipment and is beautifully crystal clear ..." You have to read deeply into these reviews to discover that, generally, those reviewers that panned the album listened to the "standard", 16bit CD and those reviewers that raved about the "crystal clear" sound and "impeccable" quality of the listening experience listened to the 24bit DVD-A version(s).

Even more interesting:

"Love Special Edition (CD + DVD) [Apple/Bea/EMI Doppel-CD]" = CD (SACD?) and DVD-A (no video apparently) (2 discs)
http://www.amazon.de/Love-Special-CD.../dp/B000JJS8TM

!!
"Love [Vinyl]" = 12 inch LP Stereo recording (2 LP discs) - available February, 2007
http://www.amazon.co.uk/Love-VINYL-B.../dp/B000M06SU4

A plethora of benchmarks === so many formats, so little time. I have the 2nd from the top of the list (purchased from Amazon.com), and thoroughly enjoy this music. My wife plays it for special occasions and when we have visitors of our age group. I will be getting the vinyl for my collection, but may never play it except for the sake of comparison with the DVD-A. After hearing the DVD-A version, we do not play the CD version except in the car as it just does not sound right = no guts, obviously compressed, although not nearly as much as previous "standard" CD variations. (It is quite obvious that the folks at Amazon.com and Amazon.co.uk don't have a clue about what to do with this ... Amazon.de, may have or not.)

Recommendations: Get the Apple published version (check the labels before you buy) that fits your playback system, hopefully you have or eventually will get a DVD player with DACs capable of reproducing the full 24 bit data. (Either stereo or db5.1 sound just fine as long as its 24bit.)

I have a hunch that Sir George is as fed up with all the variations from all of the publishers as we are, releasing this album in as many formats as possible in order to get the reviewers to pay more attention to what's "real" and what's "imagined" about production quality verses costs verses hype and hoopala verses 16bit / 24bit comparisons. ... There is apparently a SACD version (1 disc) available in Europe. If anyone finds this, please advise.

I will eventually collect all versions and if nothing but for comparisons' sake. I will also expidite my searches for 24 bit DVD-A playback for my car.