[chesebert]

I thought this is common knowledge and is a concept well-known among headfi members

 

[luidge]

Yes indeed chesebert but i thought that it was a little bit overrated and somewhat a little niche of head-fier that believe that it meant a lot in a setup. Now i believe that it make lot more of a difference than cables and maybe even amp!

 

[OverlordXenu]

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.

 

[Herandu]

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.

All true and well, but the problems can start before the transport output. A dodgy laser will send dodgy data to the optical to digital converter. And the rest,as they say, is a stream of 1's and 0's. But how accurate is the bitstream?

A good set of test discs is the Philips ones with the fingerprint marks and drilled out holes. Yes, drilled out holes! You and me know that if there is a hole in the CD, there can't be any 1's and 0's. Go tell that to the test CD, because it WILL produce an audio output. So,is that a reliable transport or not?

 

[OverlordXenu]

Quote:

Originally Posted by Herandu /img/forum/go_quote.gif All true and well, but the problems can start before the transport output. A dodgy laser will send dodgy data to the optical to digital converter. And the rest,as they say, is a stream of 1's and 0's. But how accurate is the bitstream? A good set of test discs is the Philips ones with the fingerprint marks and drilled out holes. Yes, drilled out holes! You and me know that if there is a hole in the CD, there can't be any 1's and 0's. Go tell that to the test CD, because it WILL produce an audio output. So,is that a reliable transport or not?

Does bit-perfect not mean the same bits as on the original media?

 

[Herandu]

Quote:

Originally Posted by OverlordXenu /img/forum/go_quote.gif Does bit-perfect not mean the same bits as on the original media?

And therein lies the problem. Using a test CD like the one I mentioned,it can be shown that no CD player is bit perfect. The Solomon-Reed error correction will kick in in order to output an "acceptable" signal.
I have done many tests over two decades in order to find out where the problem spots are in a CD reproduction chain. I tested various laser pick up designs, and spent a lot of money and to come to a conclusion. That's why I rate the Philips laser units and the 3 beam laser pick-ups as used by Pioneer and JVC to name a few. Those two types are more bit perfect than anything else. So look for the 3 beam laser based CD players!

 

[sejarzo]

Herandu, with your knowledge and having done research on this yourself, you may have a link to some information that I have been seeking for quite a while.

Is there anything published on the web that meaningfully compares various transports with a standard test disc to show how often the Solomon-Reed error correction kicks in? I've heard everything from "error correction happens all the time" to "it just doesn't kick in very often", but never anything truly definitive or quantitative in that regard.

Maybe a better way to put it.......how accurate are typical audio CD transports on a once through/"on the fly" basis versus current PC drives in that respect? And even if PC drives require multiple passes to ensure total accuracy, it seems to me that the state of the art in audio should be multiple reads from the disc to ensure data accuracy into a read-ahead buffer that, in turn, reclocks the data to the digital output or internal DAC.

The state of the art in optical drives today should be miles ahead of what they were back in the early 1980's. If not, then, how often does error correction for data kick in on a typical PC optical drive these days?

 

[Herandu]

To be honest with you, I spent all my time working on stand alone CD players. I tried PC drives, but like they seem to have a different technology to themselves. That part hit me hard between the eyes not so long ago when I put my Katie Malua CD in my laptop instead of my CD player. Guess what: a mpg video on the CD started playing... So much for red book on that one. This also makes error correction measurements a nuisance since the laser will go hunting for the beginning of a file rather than a particular spot on the disc. I have figured out that those anti-piracy discs are using this technique to fool a PC drive from making a bit perfect copy... A CD player doesn't hunt for a file, but a time referenced spot. To see this in action you would need an mp3 test track I made with a tune called All around the world. It has a break in it, and when a CD/mp3 player hits that break, the display on the player starts jumping as if it is reading a scratched dics! But the track is in fact an mp3 track. The timing signal is however intact, so the Solomon-Reed error correction hasn't got a clue what to do next. It therefore plays the track as if it is a scratched disc without error correction kicking in.

 

[Lazarus Short]

Quote:

Originally Posted by luidge /img/forum/go_quote.gif Well i don't agree with you Lazarus! I know upgrade my transport to a Cambridge CD6 and the toshiba was let behind in the dust! Such a glorious sound with his digital out i'm crazy about it. I now use a Lavry DA10 too, but i couldn't try it with my amp yet (need to wait for the adapters) but from the headphones out of the DA10 the music is rich and soooooo detailed. So yes i also think that the DAC part is important but dont neglect the transport my friend

You may be right, at that. I will just have to try another transport. I'm surprised to see so many others using Toshiba DVD players as transports. Maybe because they're cheap?

Laz

 

[luidge]

Cheap, easily available and have been talked about a lot here and there on the web. I bought mine because i saw some threads here. If not i would have bought any other cheap DVD player.

 

[Edwood]

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.

There is this thing called jitter. Very few, if no transport will output absolute 100% perfect data. Error is inherent and is corrected on the fly, so most people don't notice.

Even with so-called "jitter proof" DAC's, there is a limit to how jitter proof they can be.

-Ed

 

[sejarzo]

I thought jitter was that the data was correct, but just that the timing was off.

Herandu, let's just consider typical CD audio transports then and not PC drives.....how often does error correction kick in on a clean disc with a good transport?

The reason I ask is this.....I'd have to think if stray light is a problem, it's likely that the resulting errors would be very random. Significant random error would cause the error correction to kick in, would it not?

 

[Dept_of_Alchemy]

Quote:

Originally Posted by sejarzo /img/forum/go_quote.gif Herandu, let's just consider typical CD audio transports then and not PC drives.....how often does error correction kick in on a clean disc with a good transport?

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.

 

[sejarzo]

ARRRGGGHHHH.......sorry, posted in wrong thread while I had two tabs open. My bad.......

 

[luidge]

Well you might be more move by scientists than by musicians then. I for one don't care what is the process of the digital data transfer but i have pretty good ears and i can easily find different qualities to different digital gears. Your doubt may be broke by trying different source yourself. I am sure that there is a scientific explanation for this whole difference in sound, but frankly i don't care, science might give some sort of light on the case but since it is ever renewing itself so maybe in ten years the theories about digital bit perfect and all that, will be found false and my ears and the ears of lots of others not so serious members of an audio forum that post about computer dating will have won the sound war!