Digital-Recordings CD-Player Check

Digital-Recordings CD-CHECK CD-Player Test Disc

Do CD Players reproduce 100% of recorded music? Not always. Errors created by the manufacturing process, as well as dust, scratches and fingerprints, send many CD / DVD players into a tail-spin, resulting in data loss and faulty sound reproduction. This manifests itself as poor stereo imaging, lack of clarity and transient response and dynamic-range distortions. In more severe cases it leads to audible clicks, muting, looping and skipping.

So, what makes one CD player better than other?

Many factors. But one important factor has to do with the player's ability to read data from the disc. CD players have built-in D/A converters that turn the digital data on a CD into an analog signal. Ideally, all the digital data should be converted to the analog format. In reality many factors cause digital data to be lost and sound reproduction to deteriorate.

CD players have a sophisticated error correction system that allows them to recover lost data. However when the data loss is greater than a system's recovery ability, some of the signal is lost. It is then that the CD player uses concealment methods such as interpolation, data substitution or signal muting to make this loss as inaudible as possible. This results in altered and often distorted sound.

Good players rarely resort to concealment methods when reading data from the disc. They will try to faithfully recover every error.

How to find out how well a CD player reads data?

Testing for data loss is normally a complex and time-consuming procedure that requires technical background and expensive equipment to perform. This product, the CD-CHECK compact disc, is quick and easy to use. For the first time, it allows evaluation of the CD player's "error correction headroom" (i.e. player's ability to correct data errors) and "tracking" (i.e. player's ability to stay on track despite of disc surface or other errors). It is inexpensive, quick and easy to use, and more effective in evaluation of tracking and data loss.

How does CD-CHECK work?

CD-CHECK uses special digital signals in combination with disc error patterns arranged over five tracks. The five tracks contain a sequence of progressively difficult tests referred to as Check Level-1 to Check Level-5. The higher the Check Level passed the more reliable the sound reproduction of the CD player. A smooth, continuous tone indicates the player passes that Check Level. Any clicks, interruptions, skipping or looping indicates failure of a Check Level. This is however not a determination of the sound quality of a CD player. Ultimately you must still use your ears.

How does CD-CHECK rate CD player's ability to read data?

According to CD-CHECK tests, a good CD/DVD player (i.e. passing at least Check Level-3) is able to fully

• compensate for manufacturing errors, dust, fingerprints and scratches on the CD/DVD surface.
• compensate for errors generated by its own laser pickup and mechanical tracking and guidance system;
• compensate for errors generated by its own laser pickup and mechanical deterioration over time and still deliver high-quality, unaltered sound over long period of time;
• compensate for damaged and ageing CDs or those with manufacturing errors, as well as
• deliver perfect music and test signals without skipping and alteration.

What are the specific uses of CD-CHECK?

Use CD-CHECK

• when buying a new or used CD / DVD player. It is not uncommon to buy a CD player that does not pass Check Level-2. If you are the unlucky owner of such a player sooner or later you will be experiencing problems, save yourself money and frustration by testing the player before you buy it right in the store! With CD-CHECK you can do the test in just 20 seconds.
  Theoretically, CD players should be able to perfectly correct errors up to 2.47 mm across. In practice we found some players capable of correcting 2.0 mm errors. CD-CHECK simulates realistic errors of 0.375, 0.750, 1.125 and 1.500 mm. In order to cope with manufacturing errors and dust, scratches and fingerprints CD or DVD player should be able to pass at least Check Level-2 with 0.375 mm errors. You will find that there are many players which are only capable to play Check Level-1 or Check Level-2 on the CD-CHECK disc. And that is when they are new. With time their performance will dip below the acceptable level.
• to evaluate existing CD, DVD and CD-ROM players for data loss. CD players deteriorate over time. Protect your audio investment by detecting pickup defects early. Use it to determine when pickup adjustments are needed. Use it to check the adjustment effectiveness. Test your player especially prior to warranty expiration. If you are a service shop technician use CD-CHECK to help you with the repair process.
• to determine if the laser lens needs cleaning. With CD-CHECK at your disposal you don't have to clean the laser lens every 8 hours as often recommended by manufacturers of some cleaning products. Use CD-CHECK to determine when cleaning is needed (your player passes Check Level lower than that during the last test) and save the lens from unnecessary abrasions. CD-CHECK can be also used after the cleaning process to check its effectiveness.
• to evaluate the safety and effectiveness of sound-enhancing technologies. With CD-CHECK you can, for the first time, objectively evaluate various gadgets and gizmos. Digital Recordings has tested several "audiophile" technologies with it, such as "magic" markers, stabilizing rings, "magic" discs, etc.
  Many gadgets and gizmos that enhance the sound of CDs / DVDs are very difficult to test objectively. Therefore many evaluators rely on subjective audition tests, which can be very unreliable. Many of these sound enhancing technologies claim that they improve signals. Since they mostly affect only the digital signal, CD-CHECK can be used to evaluate them objectively and simply. If any of these technologies improve the playback of CD-CHECK's test signals, this clearly indicates that they reduce the number of errors generated, which in turn can lead to better sound quality. But if no change is observed, it means that a given technology does not work in this particular instance.
  Sometimes these sound-enhancing technologies actually cause the sound to deteriorate. They can even harm a player's mechanical systems, which could lead to premature mechanical failure. Some reviewers will probably hear the difference and might even prefer distorted and interpolated sound over the real thing. Internal tests at Digital Recordings and by their associates indicate that this may be the case with some technologies. With CD-CHECK, you can be sure that's what you're getting.

List of audio magazines which have the Digital-Recordings CD-CHECK disc:
- "Absolute Sound"
- "AUDIO"
- "Audio Amateur"
- "Audio Critic"
- "Audio Electronics"
- "Audio Ideas"
- "Inner Ear"
- "Recording"
- "$ensable Sound"
- "SoundStage!"
- "Stereophile"
- "Stereo Review"
- "UHF"
- "Ultimate Audio"
- "What HI*FI ?"

List of some audio manufacturers who have the Digital-Recordings CD-CHECK disc:
- Philips
- SONY
- JVC
- Panasonic / Technics
- AKG
- KRELL
- NAD
- Oracle
- NAGRA
- ARCAM
- Cello
- Clover Systems
- Hegel
- Mark Levinson
- Madrigal Labs
- Harman International
- Polyfusion Audio
- Balanced Audio Technology