CD Error Correction Tests

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

- ABEX TCD-721R

Errors total	Num: 1457211
Errors (Loudness) dB(A)	Num: 173395	Avg: -80.4 dB(A)	Max: -18.5 dB(A)
Error Muting Samples	Num: 5997	Avg: 1.2 Samples	Max: 18 Samples
Skips Samples	Num: 36	Avg: 6.0 Samples	Max: 6 Samples
Total Test Result	63.9 points (out of 100.0 maximum)
C2 Accuracy	98.6 %

The total error count was about average, and the maximum error loudness level was high at -18.5dB. There were 36 skipped samples which is high, while the drive achieved a total score of 65.4. In general, the drive 's performance was not that good with this test disc.

- ABEX TCD-726

Errors total	Num: 8438
Errors (Loudness) dB(A)	Num: 12262	Avg: -85.5 dB(A)	Max: -11.5 dB(A)
Error Muting Samples	Num: 323	Avg: 4.4 Samples	Max: 18 Samples
Skips Samples	Num: 2	Avg: 6.0 Samples	Max: 6 Samples
Total Test Result	73.9 points (out of 100.0 maximum)
C2 Accuracy	96.3 %

The Abex TCD-726 test disc is much easier for drives in general to read. Most drives manage to compile a score in the 90s with the better drives managing 100. The drive managed only 73.9, showing again that the drive's CD error correction capabilities need improving. A good reader should produce better results than these.

- 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 through a software multimedia player (i.e. Windows Media Player). Each level is considered as passed, if the tone 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-3500A	5/5	5/5	3/5	0/5	0/5

The drive successfully passed only the first two out of the five check levels for this test. Here too, the drive turned in a poor performance. Almost all drives have difficulties reading the 5th level but good quality drives can read up to the 4th level. However, most drives will pass at least the third level without any problems.

- Summary

Generally we can say that the CD error correction of the NEC ND-3500A is less than average, something that could be fixed with newer firmware releases.