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Audio reproduction: CD vs. CD-R. One more experiment

The idea of the current experiment is pretty simple and had been already discussed many times at the ixbt forum – to check the possible difference in the process of playing between the original CD (CD-ROM) and copies, recorded on CD-Rs. The playing streams were written from the digital output of the CD player to PC, equipped with the sound card with digital input. The final recordings had been compared between each other and with the results of grabbing of the above-mentioned CD’s contest with use of the PC’s CD-ROM.

The author of this article in the process of the experiment used the equipment, as follows:
As the basic sample the CD - Eric Clapton, Pilgrim, 1998, (issued by Reprise Records) had been used. I decided to choose the track, which had zero samples (digital silence recordings) in the beginning and in the end. The track had been grabbed couple of times in the CD drive Ricoh 7163 by EAC (Exact Audio Copy) and CDDAE. There were no read errors in the cases of using of the both programs. The resulting wav files were exactly the same after using of EAC, and others, grabbed by CDDAE had only difference in offsets. One of those wav files had been used to make the copies. I used it for making the special wav file with cut digital silence recordings in the beginning and in the end of the track. The resulting wav file with the length 3:47 min (10 054 676 samples) had been used in the future for comparison purpose. Let’s call it “control wav”.
I used grabbed wav to make 4 copies on the different CD-R, as follows:

Sony 650Mb 16x
ATIP: 97m 24s 11f
Disc Manufacturer: Sony Corp.
Reflective layer: Dye (Long strategy; e.g. Cyanine, Azo etc.)
Media type: CD-Recordable
Recording Speeds: min. unknown - max. Unknown
nominal Capacity: 656.40MB (74m 43s 00f / LBA: 336075)

Technological (no name) 650Mb (one of the cheapest)
ATIP: 97m 21s 45f
Disc Manufacturer: Optical Disc Manufacturing Equipment
Reflective layer: Dye (Short strategy; e.g. Phthalocyanine)
Media type: CD-Recordable
Recording Speeds: min. unknown - max. Unknown
nominal Capacity: 653.76Mb (74m 25s 00f / LBA: 334725)

SKC 800 Mb (90 min) 16x
ATIP: 96m 40s 05f
Disc Manufacturer: unknown
Reflective layer: Dye (Short strategy; e.g. Phthalocyanine)
Media type: CD-Recordable
Recording Speeds: min. unknown - max. Unknown
nominal Capacity: 703MB (79m 59s 74f / LBA: 359849)

CD-RW Verbatim 650 Mb 10x
ATIP: 97m 34s 23f
Disc Manufacturer: Mitsubishi Chemicals Corp.
Reflective layer: Phase change
Media type: CD-Rewritable
Recording Speeds: min. 4X - max. 8X
nominal Capacity: 656.40MB (74m 43s 00f / LBA: 336075)

Two tracks had been recorded on each CD-R (CD-RW) – the short one with the length 5 sec then 3 sec silence and the main one. I’ve made it by purpose – in the process of the first experiments I’ve recognized that one of the used CD players after the start of the track lost some samples in the beginning of the track. If to play one track after another, there is no loss. All CD-R had been recorded in Ricoh 7163 drive at speeds x8, CD-RW at x10.
Grabbed copies in the Ricoh were exactly the same between each other and with the wav file from the original CD-ROM.
No surprises at this step.

For recording to HDD I used the sound card Hoontech SoundTrack Digital XG with digital inputs/outputs (optical and coaxial).

All players had been connected by Hama Toshlink 1.5m cable (optical SPDIF). For experiments I used the following players:
Denon DCD-435
Marantz CD6000 (CDRW-compatible)
DVD player Toshiba SD-210 (CDRW-compatible).

The playback was started from one track before the chosen one, the recording started in the gap between the tracks. The recording software was CoolEdit 2000. The whole track had been recorded and then played. All recordings were repeated 3 times. From the resulting *.wav files the digital silence had been removed in CoolEdit manually from the beginning and the end of the track.
From the beginning of the testing recordings I’ve recognized that Marantz loses some samples after the start of playback with selection of the track by remote control – in CoolEdit the beginning of the track was completely unrecognized, and after removing of the digital silence the length of the track was smaller, then in the original. After changing of the playback procedure everything became to be correct.
Finally, the results:

Denon DCD-435
Original disc: all three recordings had the same length (10,054,676 samples) and were identical to the control wav and to each other. The comparison had been made in fc/b and in EAC (Exact Audio Copy) with “Compare WAVs” function.
CDR Sony: all three recordings were identical to each other and to the control wav.
Technological CDR: all three recordings had the same length (10,054,676 samples) but NOT identical to each other and to the control wav. We have the actual distortions in the process of playback with non-repeatable results.
The difference between one of the recorded wav and the control wav shown at the picture below:

Zoomed results:

The digital silence is followed by bursts with the length from one to few samples.

The statistics of the difference in the signals in CoolEdit:

CDR SKC 90 min.: the result is identical to the previous one with more distortions:

The difference in sounding of the CD-Rs had been easily recognized by listening. That is not surprising though – the average RMS –63 dB and even higher –54 dB – actually easily recognizable level.

Higher level of distortions at 90 min disc probably can be explained by the fact, that the optical pickup of Denon is not designed for the correct recognition of the data from a media with smaller distance between grooves and there are cross-talk distortions.

RW Verbatim: not played back.

Marantz CD6000:
Original CD – all 3 tracks had the same length (10 054 676 samples) and were identical to the control wav and between each other.

ALL TRACKS, including RW, had been exactly equal to the control wav, the track from the original CD and between each other.

DVD Toshiba SD-210:
Pretty strange results. All tracks from the original CD and from CD-Rs were different and not equal to the control wav. But I’ve got exactly the same results in different tries – all results were exactly identical in time.

The matter of differences is pretty amazing – the parts with exact identity are followed by the parts with difference in one lower bit, always with the same polarity and their position in time though even looks random, actually not random at all, and repeated with each recording. I have no idea what is the reason of such distortions.

It looks as shown at the picture below:

I guess it is enough information to make some conclusions.

The above-mentioned information published in accordance with the author’s permit.