LESS laser power and higher speeds = better readability on damaged CDs?


#1

The wonderful DV-RW250’s DVR-R07 lens degraded over time.
In my childhood, I used it a lot for DVD recording.

Then, DVD-R (surprisingly not RW) started getting unreadable, then DVD-DL followed, and CD-RW was even detected as “no disc”.
However, damage handling on pressed CDs improved drastically.

After increasing the laser potentiometer, all DVDs became readable again, also CD-RW.
But damaged CD handling became terrible. So terrible that even my father’s Technics SL-PJ26A from 1989 performs better, which actually outperforms very well generally for pressed CDs, but requires laser warm ups and also requires cooldowns after too much inactivity.
For audio CDs, the DV-RW250 jumps to the beginning of each track during reading, from last to first track. I am not sure about the purpose, because even CD-Rs with fail burns and invalid TOC are readable after a little struggle, and with full track list.

The DV-RW250 actually performs better on CDDA after warming up, due to heat, which increases conductor resistance.


Another thing are boomboxes:
If I breathe fog onto a CDDA and put it into the CD player, the fog goes away after a few seconds but the CD player laser which sounds like a water river is much louder, and damage handling deterioated, because the CD player is fooled into thinking that the CD has less reflection.


On some drives such as GDR8162B and BE14NU40, one needs to take a boost start.
First speed up, gain momentum, and read through damage.

For GDR8162B, increased speeds cause more damage noise, but lower speeds turn into hiccups. I wonder, why drives require hiccups (lens jumps from beginning to end and back) in first place.

For BE14NU40, the damage handling at minimum speed is terrible. If I accelerate first and quickly read through the damage, it handles very good.


What is a technical explaination for this phenomenon?


#2

I also noticed, that the GDR8162B reads a fake TYG02 better at higher speeds such as ×5 CAV (yes, not ×4!) than ×2 CLV.
It reaches ×8 CAV but after slowing down to ×5, it sinks into errors.


#3

Reading ability is directly related to vibrations. Every drive + disc combination (as a system) will have different resonant frequency that is directly dependent on the rotation/angular speed.


#4

Is there any further information on this?

In my tests, vibration did not have any influence.


#5

I’m saying this from mechanical engineering perspective, not strictly related to optical media and drives. To be honest it’s been a while since the last time I had to solve oscillation/vibration related stuff.

But you are saying when you vary the speed you get different results - it should be like that. Rotation of the disc causes vibrations because the mass is not ideally spread/balanced. Every drive has some sort of damper system to “fight” those unwanted oscillations. As you can see not all drives are created equal.


#6

But all drives handle DAE on heavily damaged discs better at higher speeds, due to reduced hiccupsm