Field Test: NTI Digilyzer

Feb 1, 2003 12:00 PM, By Eddie Ciletti

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How many times have you connected two pieces of digital gear together only to end up having bizarre things happen? Or worse, nothing? Enter the NTI Digilyzer, the digital bloodhound, to sniff out the problem; it is so “smart” it will even accept an analog signal, which is pretty dang cool for installers or anyone untangling a mess of mystery cables. Digilyzer allows technicians to explore previously uncharted territory.

Most digital gear is woefully lacking in its ability to display why it is unhappy. Digilyzer can display lack of data compliance, bad cables, bad bits or poor signal quality — any combination of which can contribute to lack of data integrity. Similar to its analog cousin the Minilyzer, Digilyzer is a handheld piece of test equipment with a handful of menus that can display channel-status information (three pages), distortion, PPM and RMS metering, a scope and memory to store (and recall) default Digilyzer setups and device status. The unit runs on three AA batteries (with auto shutoff) and includes an external power jack.

Digilyzer has XLR, RCA and optical digital inputs; the latter accepts both S/PDIF and ADAT Lightpipe. Any TDIF-to-ADAT converter allows the unit to read Tascam's proprietary digital format, as well. A built-in speaker is quite useful (and loud). A stereo headphone mini jack is also included.

EOA = EXCITEMENT ON ARRIVAL

As soon as Digilyzer arrived, I used it to analyze three puzzling situations. A Tascam DAT recorder pretended to go into record but did not actually put anything on tape. A detour into the machine's guts to clean the heads yielded nothing, until I realized that the unit's analog recording function was fine. I never thought to question the Alesis MasterLink that was feeding it until I substituted a Panasonic DAT deck, which balked at being in record and locked up until the power was cycled.

Equipment manufacturers are inconsistent in their implementation of digital-communications protocol: Some devices are very fussy, while others are quite forgiving. In the two DAT examples, both decks expected the sample-rate status FLAG to concur with the transmitted sample rate. Figure 1 shows side-by-side comparisons of a Technics CD player (left) and MasterLink, respective examples of consumer and pro formats.

For this discussion, note the reverse video “FS NO ID,” which indicates that the sample-rate FLAG had not been set. In this snapshot, the MasterLink is also transmitting at 88.2 kHz, but not at the time of the DAT trouble (just in case you're really paying attention). By not setting the sample-rate FLAG, the Masterlink did not comply with the specification, a problem that was remedied in later production units.

In another instance, the AES output of a Sony PCM-R500 did not transmit a “clean” signal, thus wreaking havoc with a CD burner but not causing any immediate, obvious trouble with other gear. Notice in Fig. 1 (CD player) the rectangle right of optical is “open,” indicating good data. In Fig. 2 (PCM-R500), the rectangle is solid black — bad data, but not bad enough to mute audio. Figure 2 shows a flashing “FAULT.”

Digilyzer is a very powerful tool if you know where to look. Whether the data is good, bad or out of compliance, Digilyzer is tolerant and does its best to translate audio that other devices will not. Tolerance is good only if it doesn't lure us into a false sense of data security. Then again, have you ever felt something was wrong with the sound, but couldn't quite put your finger on it? In conjunction with the Minirator (or any low-distortion oscillator), Digilyzer can measure distortion, as well as provide a “heads-up” clue as to the cause of the problem.

For most of the tests, Digilyzer was a destination on a Z-Systems Digital Detangler, hence the optical indication on the display, even though many different sources were tested. Figure 3 shows the AES input being tested, along with the ability to display the incoming signal level; in this case, 4.7 volts P-P.

Note also that the number in the center square (all but Fig. 1) indicates the page number — there are three to check channel status, plus a bit-status page. Figure 4a/4b demonstrates how bit depth is displayed for a 16-bit and 24-bit signal, respectively.

Digilyzer can provide hours of fun for checking out every possible signal source in the studio, on the road or anywhere. With additional reading (via manual and online) and testing, Digilyzer becomes an even more valuable tool. It doesn't blare out any warning tones and can't do more than flash a warning on the appropriate page, so some problems might not be obvious if you don't know where to look. Hence, the importance of the “signal-quality rectangle” as pointed out earlier.

At a $1,590 MSRP, Digilyzer costs more than I expected, considering Minilyzer ($579) is about a third of that price. Still, time is money, and Digilyzer saves time and speculation. From 16 bits to 24 bits, 32 kHz to 96 kHz, Digilyzer tells you the good, the bad and the ugly.

NTI North America, 3520 Griffith St., St. Laurent, Quebec H4T 1A7; 800/661-6388; fax 514/344-5221; www.ntinstruments.com.






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