[Sleestack]

Quote:

Originally Posted by Glassman and who said just because they are mega, I mean mega-bucks, they ought to be done properly? certainly not..

Price certainly is no guarantee. That being said, I think they are all solid transports.

As for an earlier question regarding using a $100 transport.. I don't have a $100 transport, but I do have had the XCD-88 and am loaning out my XCD-99. I never did side-by-side comparisons, but I never had a problem using the XCD-88 as a transport. I'll try to do some critical evaluations when my XCD-99 gets back.

 

[Teerawit]

Quote:

Originally Posted by Glassman and who said just because they are mega, I mean mega-bucks, they ought to be done properly? certainly not..

Well, since we are at both ends of the extreme spectrum here, I would "assume" that a mega-source would generally serve as a better transport than a $100 source...

ie. sound better, even if the mega sources aren't "done properly"

 

[pcolbeck]

[QUOTE I would "assume" that a mega-source would generally serve as a better transport than a $100 source...

ie. sound better, even if the mega sources aren't "done properly"[/QUOTE]

I wouldn't count on it, remember a cheapo £20 transport that comes with a home PC reads data of a CD perfectly, if it didnt the computer program wouldn't work as computers have no tolerance at all for any incorrect data. What the cheap transport mat not be able to do is read data off the CD perfectly at a quick enough rate to keep the buffer filled for audio application. Audio CD players have to get the data off an CD and pass it along the chain at a specific and exact clock rate, for data purposes whenever will do. If we are just using a CD as transport theorretically it could fill a buffer at its lesuire and then you could use an expensive clock to clocjk the data out to the next part of the chain.

 

[Teerawit]

Quote:

Originally Posted by pcolbeck I wouldn't count on it, remember a cheapo £20 transport that comes with a home PC reads data of a CD perfectly, if it didnt the computer program wouldn't work as computers have no tolerance at all for any incorrect data. What the cheap transport mat not be able to do is read data off the CD perfectly at a quick enough rate to keep the buffer filled for audio application. Audio CD players have to get the data off an CD and pass it along the chain at a specific and exact clock rate, for data purposes whenever will do. If we are just using a CD as transport theorretically it could fill a buffer at its lesuire and then you could use an expensive clock to clocjk the data out to the next part of the chain.

That was what I was referring to...thanks for explaining it though. I knew I wasn't crazy...

 

[DatHak512]

So i guess what i'm reading is that the $100 player will probably have some sort of a buffer ('cause otherwise it wouldn't work at all, or would skip if even the slightest drop in CD speed occured) and so if i'm using a digital out it won't matter if i'm using a cheap CDP or an expensive one? Sorry if i got that wrong, but i was following the convo, up until post #11, and then it all started going down-hill from there

. Does that sound about right?

 

[Garbz]

not necessarily but it depends between players. What i can add though is that often some cheap players transport wise can be an absolute gem. The Pioneer DV-676 makes an excellent transport (poorer analogues though).

 

[clarke68]

Quote:

Originally Posted by Sleestack As for an earlier question regarding using a $100 transport.. I don't have a $100 transport, but I do have had the XCD-88 and am loaning out my XCD-99. I never did side-by-side comparisons, but I never had a problem using the XCD-88 as a transport. I'll try to do some critical evaluations when my XCD-99 gets back.

FWIW, I A/B tested the XCD-99 as a transport against one of my modded NEC 602s. After about an hour of listening, I was unable to find any consistent difference between them.

 

[Northern Oak]

Quote:

Originally Posted by Glassman it has something to do with the laser pickup, not optical output.. while I cannot tell for sure, I guess it's calibrating laser power based on reflectivity of the particular disc inserted.. nothing to do with jitter again, but it might improve the reliability of the transport mechanism and help reading RW or simply hard to read discs.. should have no effect on sound when playing CDs in good condition.. you can always check for yourself, each CD player nowadays has digital output, which you can connect to computer soundcard and record, then compare with properly ripped track..

Here's my 2 cents worth:

In the laser pick up module, there's the laser diode as well as the photodiode or photodetector. The laser diode emits the laser beam which hits the CD's pits and lands and the reflected beam is sensed by the photodiode, which then converts it to photodiode current.

This current, however, is usually small/weak, which means inherently, the SNR (signal to noise ratio) is pretty low, therefore the preamp helps to amplify the signal, thereby increasing the SNR.

As for whether it's used for adjusting the laser optical power, that is an interesting suggestion. I'm not certain if that is in use but generally, that would require a feedback loop where the photodiode current is monitored, perhaps by a microcontroller/microprocessor which then controls the laser driver.

If such circuits exist commonly in our players, then chances are that the lasers would be able to self-calibrate over time to ensure good optical emission. Frankly, I really don't know if it's in use.