how can digital be different

Hi everyone

me and my friend (whos not into hifi) have been arguing recently about how digital can be different. I think there must be differences because people wouldnt spend there money on better transports if there wasnt would they?

well the main two things we have been arguing about are transports and digital cables.

i can understand how transports could sound different because of microphonics, power supply etc. but what about the actual reading of the cd. How can green pen or the special paint naim paint on the underside of the case make a difference?

and how can one digital cable sound different to another one when are they r doing is transferring 1s and 0s.

does anybody know any technical reasons so i can shut my mate up!!

Cheers

Chris

 

:duck: :WMarrives

 

uh oh, does that mean ive started something bad? sorry, but my mate is such an opinionated git and i wanna shut him up!

ive just noticed the thread in the "reviews" forum about the green pen and the de-magic cd, so sorry about that! but im still curious about digital cables.

Chris

 

Hi Chris,

This recent thread should keep you busy :

https://www.audio-forums.com/as-rediect/showthread.php?s=&threadid=2682

 

Some more threads which may be of interest:

https://www.audio-forums.com/as-rediect/showthread.php?s=&threadid=2781
https://www.audio-forums.com/as-rediect/showthread.php?s=&threadid=2666

Search for the forum for discussion on digital cables and also the DAC64 (there was very big DAC64 discussion a while back about whether it was suseptible to transport differences and whether its buffer memory helped in this regard, can't be bothered to search for it though now as I'm off to bed).

HTH

 

I doubt very much you'll manage to shut your friend up unless you can sit him down in front of your HiFi and demonstrate the differences to him, and even then you may struggle...

 

because audio cd's are read in realtime errors are very important. with computer cd's the data can be re-read a number of times to ensure correctness. for (most) audio transports this is not possible as the dac expects it's data NOW. this means that spurious reflections, refractions, power fluctuations, rf noise, mains noise, etc. could all cause misread data. if an error occurs then the error correction kicks in and the chips make a 'best guess' as to what the corrupt data should be. this guess however is not the origonal data and so distortion occurs.
cheers


julian

 

Chris, best to keep arguing between yourselves mate as everyone knows, its just 1's and 0's CD drives and kettle leads for me

 

It's like a Red Rag to a Bull

Here we go again...

Computer drives run at much higher speed, and still rarely need to re-read data..

Been reading Stereophile again?

Just about every disc "read error" is completely masked by the very robust Reed-Solomon REDUNDACY code, if you read enough of the data correctly, you can recover the data perfectly. Interpolation might happen with a really bad disc but even then how audible that process is also questionable.

Either the disc reads and the data is recovered perfectly or the disc is so badly scratched that it doesn't read at all. There is no subtle distortion to speak of.

If Andy Weekes and Wm are game, we can now have a ding-dong argument about clock jitter and white-phase noise.

 

Sorry Andy (T), I'll politely decline to day, I've just got so much stuff do for the forthcoming event mate, however I'll leave you with this, 'By reducing the jitter' to a far lower point, does it make Better?, maybe a bit of 'rough' isn't such a bad thing maybe?
I feel Paul Ranson should be in on this 2 (had a useful chat about this at Ju's bake off), he has some interesting theories on this digital transferance of 'raw data' to the output sections, worth a more indepth look, which I would be up for I might add.
Have fun Wm
PS the benchmark is coming on well Andy

 

Read this... :JPS:

 

I've not read it all, but there's so much wilful distortion and obfuscation of the truth going on on the first page I have my doubts as to the credibility of any of the rest of it.

 

andy,
from what i remember (and i'm a tad rusty i admit) reed-solomon is best at long runs of error as you'd get with a scratch or smear on a cd. if it's randomly distibuted and quite frequent then it's not so hot.
cheers


julian

 

For instance...

 

If this is true - and I'm not saying it isn't but have to admit a certain scepticism - then why don't they build a small cache as standard into disc players so that they can read ahead and reread should there be a problem (in fact isn't that how the G-Shock systems built into portable CD and MD players work anyway?)

 

This may/may not have any bearing on preceedings


"As an example, look at the ubiquitous Philips and Sony CD mechanisms that populate the majority of high-end CD playback systems. Mediocre isolation of the laser mechanism and inferior construction makes them easily susceptible to structural and airborne vibrations. A slightly eccentric or warped CD can wreak havoc on these lightweight mechanisms greatly compromising the player's performance! Compound this by the fact that audiophile's tend to locate their CD players somewhere between the loudspeakers or in proximity to a room corner. Areas where vibration will have the greatest impact! Imagine how difficult this makes it for the laser mechanism to track the data. It is a minor miracle of engineering that a player can make music in such a hostile environment. It was for this very reason that Philips and Sony developed the Reed/Solomon error correction scheme. The Reed/Solomon code was designed to repair, reconstruct and maintain the flow of data under less than ideal conditions. And, even though the Reed/Solomon error correction keeps the data intact, strong vibrations still force the laser mechanism to work much harder to maintain focus. As a result, the mechanism draws significantly more current from the power supply. This affects power distribution to other critical areas in the player and degrades overall performance.

For your reference, the CD Redbook standard defines the specifications for a CD data track as:

Data track width = 0.5 Micron (0.00001969â€Â)
Data word length = 8.0 Microns (0.0003150â€Â)
Data track pitch (distance between tracks) = 1.5 Microns (0.0000591â€Â).
This helps illustrate the precision that a laser assembly must possess to properly track CD data [DVD tolerances are tighter]. To put this into perspective, 100 CD data tracks could easily be written on the circumference of a human hair. The laser mechanism tracks this data in a continuous outward spiral from the inside [Table of Contents] to the outer edge of the compact disc. It continuously adjusts the disc's rotational speed as it travels to maintain an even and uninterrupted flow of data. "

 

Plan of Action,

Listen to your favourite CD on a Marantz 6000SE

Then listen to same CD on a Wadia 861 played through the same system. Just to keep the anoraks happy make sure someone else performs the switchover for you and that you wear a balaclava back to front whilst he does it.

If you heard a difference then stop wasting time wondering why and boring everyone senseless.

If you didn't, then you are clearly deaf and should possibly re-route the hobby channel towards videophilia (just remember to take off the balaclava)

 

Outstanding

 

Uncle ants,
simple answer is cost. also the 'tweakier' the 'solution' the more of us gullable fools will be attracted to it. i believe meridian does use a buffer system similar to this and of course there is the chord dac 64 which also uses a buffer memory (although not for this purpose) so there are some manufacturers out there doing this.

cheers

julian

 

Surely the cost would be relatively small?

Is there an actual book? And is it red?