[Duncan]

Strange, and maybe unanswerable question here...

What part of the CD player process dictates how well the CD player will read a CD?

The reason I ask... one particular (old) CD I have, the last track was unplayable (skipping, reading random parts of the track... total silence as was unable to track etc....) on my D121, D231, D345, D777, E905 and EJ1000 discmen, and also my Pioneer PD202 and Marantz CD63se CD players...

Just listening to this particular CD on my Aura... and, played as sweetly as anything, no skips, no pops... nothing, apart from the tune

Is there a way to tell, in mechanism, dac, or whatever ~ whether a particular cd player will read 'faulty' discs ~ or have I just struck real lucky with this player?

thanks

 

[balcar]

Duncan,

I came across a web site recently that had a lot of information about CD Player error checking, including a review of a reasonably priced CD that is especially set up to do error checking. I recall author pointing out that most players can pass tests 1 thru 3, but 4 and 5 were more difficult.

I am looking for the website address, and will send it to you when I locate it. I thought I bookmarked it, but perhaps not, since I can't seem to find it.

 

[Duncan]

Thanks balcar

 

[DanG]

As far as I know, the inability to read data off of a digital disc can be the fault of one part of the CD player or a combination of several. This is the process by which a CD player reads the information from the CD:
1. Reading laser is shot at the disc surface while CD is spinning.
2. Laser light bounces off the CD surface and into the reading filter to determine whether the information was a "0" or a "1."
3. The string of these bits is sent to the DAC, where digital to analogue conversion takes place.

It seems most likely to me that a problem in reading data off of a CD would arise if the laser lens is dirty (transport issue), if the disc isn't spinning as evenly (that is, if it wobbles or shakes at all while spinning) (transport issue), if the CD's surface is scratched (again, transport issue -- how well can the laser-reader determine if it's getting a 1 or a 0?), or if your CD player reads Japanese instead of binary code (factory issue -- send back for re-indoctrination). My guess is that it's just scratches which can account for this strangeness. Other than that, maybe there's something wrong with the clear plastic that covers the CD's information surface. If it's refracting the light it might affect how the binary information is read.

 

[DanG]

I don't think it would be an issue of error checking as the entire track is unreadable to the other players. It seems highly unlikely that the error-checking ability of the new CD player is that much better than of the other players.

 

[balcar]

Duncan,

Found it. The company is Digital Recordings

Click on CD Check. The disc sells for $25.

The company also sells a device they call an "Acoustic Callibrator" that works in conjunction with the Radio Shack sound level meter to compare headphones, etc. It's a bit expensive, but for someone who is looking for a quantitative way to evaluate headphones, it would be nice to have.

 

[Dusty Chalk]

The problems with playing the last track on older CD players is usually that the wobble on the outer edges is enough that the laser reading part can't happen. This means that either your good player either has a better, more stable transport, and therefore there is less wobble at the outer edge, or it has a bigger/better capturing area (which can't always work, because if you get reflections in the wrong direction, you'll still get bad data), or some combination of the two. Also, the extension of the lens isn't always set up to work that far out, so is less accurate because it's at the end of it's run, and has its own wobble problems.