Transport do matter!!!
Sep 20, 2007 at 3:46 PM Post #31 of 63
Sorry about my mistake above, Luidge. Another current thread refers to a "tweak" using blue-green paper to cut down supposed errors due to stray light reflections in transports (the vendor of the stuff has the web site with all sorts of glowing comments about the tweak from anonymous posters and has the computer dating links on it.) Both threads effectively center on a common question--are transports really passing on a lot of erroneous data to DACs, or not?

I don't quite understand what you mean by "theories about digital bit perfect" though.

You are not, I hope, suggesting that transports that don't provide an accurate read of the disc data possibly sound better than those that do?
 
Sep 20, 2007 at 3:59 PM Post #32 of 63
Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif
Sorry about my mistake above, Luidge. Another current thread refers to a "tweak" using blue-green paper to cut down supposed errors due to stray light reflections in transports (the vendor of the stuff has the web site with all sorts of glowing comments about the tweak from anonymous posters and has the computer dating links on it.) Both threads effectively center on a common question--are transports really passing on a lot of erroneous data to DACs, or not?

I don't quite understand what you mean by "theories about digital bit perfect" though.

You are not, I hope, suggesting that transports that don't provide an accurate read of the disc data possibly sound better than those that do?


Oh i didn't understand that part right, sorry. I also think that this kind of tweak are giberish even though i might be wrong. As for the bit perfect part i ain't saying that an unaccurate read is better, i was only telling that different CD player wich are suppose to deliver bit perfect data don't sound equal to me when played in the same DAC. I don't know if it's because one source is giving more errors or whatnot, only that one SQ is better than the other. Sorry if my ideas aren't well explained as my first language is french.
 
Sep 20, 2007 at 5:12 PM Post #33 of 63
Quote:

Originally Posted by Dept_of_Alchemy /img/forum/go_quote.gif
If you ever own a DAC that tells you when error correction is on you'll see that it's hardly ever on at all. And this whole thing about pico second jitter is quite fantastic, why in the world would our ears be spec to detect pico second timing variations? It doesn't make any evolutionary sense.


It's not that the analog signal simply isn't generated a picosecond late.

While I don't have all the background to understand or explain it all, if the bit-perfect/correct data is fed into the D/A process at slightly the wrong time, the resulting analog output contains spurious distortions.
 
Sep 20, 2007 at 6:18 PM Post #34 of 63
Quote:

Originally Posted by OverlordXenu /img/forum/go_quote.gif
As long as the transport outputs bit perfect audio and does not resample, it will sound the same as any other transport that does the same. Why? Because bits are bits. 101010101 will sound the same as 101010101 no matter the transport used, it will stay 101010101.


You must never have heard of the term "jitter"?

As they say, "The right data at the wrong time is the wrong data."
 
Sep 20, 2007 at 6:57 PM Post #35 of 63
Quote:

Originally Posted by luidge /img/forum/go_quote.gif
Well you might be more move by scientists than by musicians then.


I actually kinda do.
cool.gif


Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif
It's not that the analog signal simply isn't generated a picosecond late.

While I don't have all the background to understand or explain it all, if the bit-perfect/correct data is fed into the D/A process at slightly the wrong time, the resulting analog output contains spurious distortions.


Well that's interesting, first time I heard that. Do you have a link?
 
Sep 20, 2007 at 7:29 PM Post #36 of 63
What noone seems to be able to explain is why can we make copy-from-copy-from-copy of software CDs and they still work fine. If the reading capabilities of $50 DVD units are so bad, how is this possible?. All this jitter story seems like snake oil to me.
 
Sep 20, 2007 at 7:48 PM Post #37 of 63
Copying something is very different from playing audio in real time.
 
Sep 20, 2007 at 8:31 PM Post #38 of 63
Quote:

Originally Posted by fjf /img/forum/go_quote.gif
What noone seems to be able to explain is why can we make copy-from-copy-from-copy of software CDs and they still work fine. If the reading capabilities of $50 DVD units are so bad, how is this possible?. All this jitter story seems like snake oil to me.


Jitter values of certain iCs used in a DAC are mentioned in the component datasheets. Component manufacturers are not in the process of quoting figures that are snake oil.

Reed-Solomon coding is a key component of a CD or DVD. It is a strong error correction coding. In the CD two layers of Reed-Solomon coding separated by a 28-way convolutional interleaver yields a scheme called Cross-Interleaved Reed Solomon Coding (CIRC). This code can correct up to 2 byte errors per 32-byte block of 1's and 0's. More importantly, it flags as erasures any uncorrectable blocks, i.e., blocks with more than 2 byte errors.

The result is a CIRC that can completely correct error bursts up to 4000 bits, or about 2.5 mm on the disc surface. This code is so strong that most CD playback errors are almost certainly caused by tracking errors that cause the laser to jump track, not by uncorrectable error bursts. At the same time, it allows for even a cheap DVD or CD player with a dodgy laser pick-up to reproduce a content of sorts. A better player with a high quality laser pick-up, excellent vibration damping, and a pristine CD or DVD on the platter will produce the least number of errors. However, there is still a long way to go before that digital signal is converted to an analogue one. By that time it can run into all sorts of error problems, not just jitter. So just concentrating on jitter is over simplifying the problems that are possible.
 
Sep 20, 2007 at 9:27 PM Post #41 of 63
Quote:

Originally Posted by fjf /img/forum/go_quote.gif
What noone seems to be able to explain is why can we make copy-from-copy-from-copy of software CDs and they still work fine. If the reading capabilities of $50 DVD units are so bad, how is this possible?. All this jitter story seems like snake oil to me.


Honestly, I think this whole paranoia over jitter is a crock of BS (a good DAC will correct for it), but copying is very different from playing real time.

Using EAC in secure mode, with everything correctly set (and there is nothing better than EAC...), it reads the disk over and over again, correcting errors (to a point, of course).

For me, a CD in good condition takes about 20 minutes to rip via EAC, while encoding to FLAC at the same time.
 
Sep 20, 2007 at 9:51 PM Post #43 of 63
Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif
Still, Herandu..........say we have a better than average transport and a pristine disc. How often does error correction kick in?


In such a situation it would be reasonable to assume that error correction is at its minimum. Unlike analogue, a sine wave on a CD is not a continuous string of data on the disc. The actual data that makes up the sine wave is spread over a number of data blocks. It's this spreading out of the data that makes it possible for error correction. I don't know of any simple method to measure when error correction kicks in. What I have used as a guide to how much more error correction comes into play is by judging the eye pattern from the laser pick-up. A nice clean pattern means less errors being registered. That's why I recommend 3 beam laser pick up players. They are less error prone.

There is a very informative article here that explains it better than I ever could.
 
Sep 20, 2007 at 10:55 PM Post #45 of 63
Quote:

Originally Posted by OverlordXenu /img/forum/go_quote.gif
I wouldn't call Stereophile a reputable source, in the least...


What I referenced was a technical article/explanation, not an equipment review.
 
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