Error Correction Tests

In the following tests we check the drive's behaviour when reading scratched / defective audio discs. The test discs used were the ABEX series from ALMEDIO.

- ABEX TCD-721R

Errors total	Num: 3621791
Errors (Loudness) dB(A)	Num: 592873	Avg: -72.1 dB(A)	Max: -18.4 dB(A)
Error Muting Samples	Num: 127881	Avg: 1.0 Samples	Max: 89 Samples
Skips Samples	Num: 10538	Avg: 6.3 Samples	Max: 12 Samples
Total Test Result	65.0 points (out of 100.0 maximum)
C2 Accuracy	99.6 %

The performance with this disc is not the best. The total error count was extremely high, as was the maximum loudness error level at -18.4dB and the number of skipped samples. The final score of 65.0 is rather low and is indicativee of the poor performance of the drive.

- ABEX TCD-726

Errors total	Num: 4100
Errors (Loudness) dB(A)	Num: 6622	Avg: -84.4 dB(A)	Max: -25.1 dB(A)
Error Muting Samples	Num: 63	Avg: 4.2 Samples	Max: 102 Samples
Skips Samples	Num: 0	Avg: 0 Samples	Max: 0 Samples
Total Test Result	81.2 points (out of 100.0 maximum)
C2 Accuracy	100.0 %

The Abex TCD-726 test disc is much easier for drives in general to read. The NEC ND-2500A managed to do better this time, but the score of 81.2 is low, especially when most drives score somewhere in the 90's and the better drives close to 100.

- CD-Check Audio Test Disc

The CD-Check Test Disc is a very useful tool for evaluating the Sound Reproduction / Error correction capabilities of a CD player. The disc offers a signal combination with disc error patterns to rate the drive's abilities to read music and reproduce it completely. Five tracks on the disc contain a sequence of progressively more difficult tests. These tracks are referred to as Check Level-1 through Check Level-5.

The tracks are reproduced (played) through a software multimedia player (i.e. Windows Media Player). Each level is considered as passed, if the tone coming out from the speakers is smooth, continuous without interruptions, skipping or looping. The higher the Check Level passed, the more reliable the sound reproduction of the tested drive.

Error Level	1	2	3	4	5
NEC ND-2500A	5/5	5/5	0/5	0/5	0/5

The drive successfully passed only the first two out of the five check levels for this test. Once again the drive had poor performance. While it is accepted that the 5th level is difficult to read with almost all but the very best of drives, most drives will pass the third level and a good drive the 4th.

- Summary

Test Disc	Reading Speed	Score
ABEX TCD-721R	Max	65.0
ABEX TCD-726		81.2
Average Score		73.1

The NEC ND-2500A managed an average score of 73.1 out of 100. This is a very low score and poses some doubts as to the abilities of the drive to read and correct defective discs.