The Analog Compact Disc Clover Systems QA-101 CD Analyzer

Sidebar: Clover Systems QA-101 CD Analyzer

Looking at error rates on CDs was once the domain of specialized test instruments costing tens of thousands of dollars. These CD analyzers were highly sophisticated, and often provided all kinds of statistical and graphic plotting functions useful when characterizing the quality of large quantities of CDs. The high cost and complexity of CD analyzers excluded all but CD replicators from knowing how well—or how poorly—CDs were made.

All that has changed with a new CD analyzer made by Clover Systems of Laguna Beach, California. The Clover QA-101 is as easy to use as a CD player, and, at $3750, costs less than some high-end transports.

Its low price and simple operation make the QA-101 ideal for those who need to check disc quality on a small scale: record companies, CD-ROM publishers, CD retailers, and stores selling used CDs. Retailers who buy and sell used CDs could check the quality of discs before they buy, and reject those that have been abused. Moreover, the QA-101 could demonstrate to potential purchasers of used discs that the discs are in good condition.

Another application for the QA-101 is checking the disc quality of CD-Rs used as CD masters. CD replicators can now accept a write-once CD as the master, rather than a clunky and expensive ¾" U-Matic tape. Mastering houses can be certain that the master disc they send to the pressing plant has no uncorrectable errors.

The QA-101 starts life as a Philips CD950 CD player. The modifications access the error flags inside the player and present the error data numerically on the machine's custom display. The front panel has two buttons that select which error type is shown. Specifically, the "mode" button scrolls through permutations of the error selected (overall number of the error, number of peak errors, and number of average errors). The type of error displayed is selected by the "error" button, and error rates are continuously updated as the disc plays. At the end of the disc, simply scroll through the error types by pushing the two front-panel buttons, and record the results. To warn of uncorrectable errors, a front-panel LED comes on and stays on when an uncorrectable (E32) error is encountered.

The QA-101 can be augmented with Clover Systems' QA-Net software ($375), which interfaces up to four QA-101s to a PC. The PC collects the error data from each QA-101 and imports the data into Microsoft Excel for analysis and graphic display (fig.1).

Fig.1 Clover Systems' QA-Net software exports CD-quality data to Microsoft Excel for graphical analysis. This example shows a disc's BLER (Block Error Rate) plotted against playing time (bottom) with overall error statistics inset.

The QA-101's rear panel holds two BNC jacks, one supplying the buffered HF signal, the other the tracking signal. When connected to an oscilloscope, these jacks permit easy examination of the HF and tracking signals. The excellent owner's manual includes a full description of what to look for in these signals, as well as what level of errors constitutes poor disc performance.

The QA-101 is available from Clover Systems, 31642 S. Coast Highway, Suite 101, Laguna Beach, CA 92677. Tel: (714) 499-9566. Fax: (714) 499-4844.—Robert Harley

Hydranix's picture

If the digital data is the same once it has been recovered from the disc, then the digital binary data entering the pins of the DAC IC are the same, thus the DAC produces an analog signal that in theory should be the same.

Once the disc has been read, the data is buffered to memory before reaching the DAC IC (this is how anti-skip works and is on every CD player made since the 1990s, portible, home, car, or computer). So this whole article is complete BS.