Most CDs I have will extract at the Plextor's (PX-708A) top speed . But every so often (maybe 1 in 20 discs), the drive will slow to 8x. I'm not talking about a slowdown during DAE, but upon inserting the disc in the drive.

And I can't change the speed back to the maximum. In Plextools, I can change the speed in the dropdown box, but if I leave that page and return to it, it's stuck at 8x. EAC will not be able to change the drive's speed either.

This happens on pristine discs, in some cases right out of the cellophane.

It's as if the drive senses something about that disc and forces the maximum to be 8x.

Does anyone know why?

I don't know what's happening, but just wanted to say that I get the same behaviour from my PX-712A (firmware 1.05).

What I have noticed is that it happened more frequently on the classical CDs I was ripping, which were mainly bought during the late 1980s. Most of my rock CDs were bought later than that. (Back in the 80s I bought classical on CD and rock on vinyl). So I put it down to something different about the way CDs were made in the early days of the format. But I notice you mention it happens on brand new discs (out of the cellophane), so I suppose that theory doesn't hold up.

I too would be very interested in the cause of this.

When a Plextor drive initialises a disc, it determines the optimal read speed and thereby imposes a limit that you cannot exceed on hardware level - which is a good thing.

I have a few discs like that as well. They are almost all mint. Certainly nothing to do with scratches. I suspect the slowdown is due to either the disc's low reflectivity or poor balance. Of course, it could be BLER, jitter, beta or any of a host of other tiny factors.

I think I'll run a few tests with PlexTools Pro on a couple of such CDs and report back here.

Update
Here is one example: Amber's self-titled CD (1999, ZYX GDC 20537-2). A C1/C2 test revealed a very high C1 level:
C1 avg............28.0
C1 max:..........80.0
C1 total:..119999.0

80 C1s a second is within the specs (220), but for anyone accustomed to burning quality media (like Taiyo Yuden) the numbers are alarming.

The beta and jitter test results look reasonable, so it may be the BLER after all.

edit: typo

That makes sense. I took your lead and measured a couple of CDs:

One that DAE'd at top speed (about 37x by the end of the disc) gave these results:
C1 avg: 2.2
C1 max: 25
C1 tot: 9640
(no C2 or CU errors)

The other, that DAE'd at about 7x, gave these results:
C1 avg: 13.0
C1 max: 66
C1 tot: 45160
C2 avg: 0
C2 max: 4
C2 tot: 7
(no CU errors)

The second disc is well within redbook spec, but I suppose it must be a little harder to read. What amazes me is that the Plextor drive manages to establish this before you start extracting. Perhaps it figures it out while reading the TOC?

Not quite within the specs, unless the disc is 14 hours long <g>. That many C2s are definitely a cause for concern - I would back up that disc to a quality CD-R (like the Maxell CD-R Pro referenced in my previous post) immediately.

It would be indeed interesting to know how Plextors determine the optimum reading speed. I doubt it has anything to do with the TOC, more likely a few quick samples of the data here and there. Or maybe it is a Plextor trade secret?

This probably isn't just a Plextor-specific behavior. My LG GCE-8520B also slows down on certain discs before DAE has begun.

A disc that comes to mind is William Orbit - Strange Cargo III. The disc is mint in appearance, but extracts at about half the speed of most of my other titles.

My Sony DDU-1621 sometimes behaves the similar way too, except that it sets the speed to 16x (just after inserting a disc, it doesn't speed-up to anything faster at all then), sometimes I can force read speed of 24x with Nero DriveSpeed. These are the speeds typical for reading CD-RW discs for that drive (other CDs it should be able to read at 40x). I also think that it must be something related to TOC or other early areas of the discs where quality is determined (the drive surely doesn't perform a full disc scan to get the average).

Thanks for the responses so far. But let me add to the mystery...

I had been extracting discs all morning (I'm converting my whole CD collection to lossless FLAC) when I came across another disc that caused my Plextor to slow to 8x. I had to leave and didn't have time to extract it, so I shut down.

When I returned (about 3 hours later), I put the disc in and was able to extract it at 32x (not *quite* top speed, but the next setting down).

Is there a possibility that the drive could be overheating (or something like that)?

Again, here it happens the same too - sometimes I just need to reinsert the disc to be able to read it at full speed. Maybe a question of some scrap of dust wandering in the drive or on the disc?

Did anybody ever find a definitive solution to this "mistery"? I'm facing a similar situation and stumbled upon this thread using the search function.

I use a Plextor Premium.

I was the OP of this thread.

No mystery. Like others have said, the Plextor senses the optimal speed for each disc and sets the maximum speed accordingly. Better that than a higher speed with the risk of errors.

The only incident that baffled me is when it slowed to 8x on a disc and later went to 32x on the same disc. I can't remember the circumstances. Maybe I upgraded the firmware.

I think this would have been done by the extraction software not the drive.

Nope, the drive sets the maximum speed.

Just to add to this mystery, right now I have a Plextor 716A and a Sony 720A all latest firmware. I am comparing them both.
I burned a CDR with the plextor with 19 tracks
Using Nero
The sony ripped the CDR in 4 minutes
The plextor ripped it in >12min
Using plextools
The sony could not rip the cd
The plextor was at 8x (as stated in other parts of this thread) ripped about the same speed as the Nero test above.

"ech3" might be right, "Better that than a higher speed with the risk of errors.
" One thing I will do is see if the Sony really ripped the tracks accurately. I cannot actually hear any issues with them, but maybe the bits are different.
Even if the Plextor reads the info more accurately, I wish I can choose to speed things up at the risk of errors that I may not care about.

Other comparisons I did. times are Plextor/Sony
rip Charlies Angles DVD 8:42/12:46
XCOPY files from burned CA DVD 6:36/11:01
BURN riped CA DVD 15:01/10:00 (Sony won this one)
Burn Music disc 4:31/6:21

Hi, I'm also experiencing weird (random ?) slowdowns with a PX 716, also before DAE begins (gap detection takes a lot of time too and makes little chirping noises), but the speed is taken down to 3.6x, not 8x, making things even worse ! Restarting EAC or even Windows doesn't seem to change anything.

Once this speed is set, it stays set for any other CD I insert. Strangely, things went back to normal after turning off the computer for a while. I don't think there is any chance of this being a heat issue since I only rip 4 or 5 CDs before getting bored

Perhaps it's to do with the centre of the drive (uhh, 'spindle'?) being just slightly out of line?

florent, that is what I found .... I rip 2 DVD's the first one is at 10x .. the second 8x .. then at some point slows to 2x and stays there. I then put the first DVD back in and it rips at 2x. Turn the machine off for a bit, put the first DVD in and it starts ripping at 10x ... cancel it, put the second one in and it rips at 10x.
I just replaced my mother board and I thought that i didn't bond the CPU to the heat sink .. so it was over heating .. I wish I had the time to look into this. At some point I might have to.

Acid8000 : Not sure, my computer (including PX716) is brand new (2 months old, and I just started ripping)

Sabre150 : weird indeed. I haven't tested DVDs though, just CD ripping with EAC.