Field Report: NTI Digilyzer DL1

Oct 1, 2003 12:00 PM, by Eddie Ciletti

How many times have you connected two pieces of digital equipment together only to end up having bizarre things happen? Or even worse, nothing happen? Luckily, there is the NTI Digilyzer, a digital bloodhound, to sniff out the problem. It is so smart it will even accept an analog signal.

Most digital equipment is woefully lacking in its ability to display why it is unhappy. The 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, the Digilyzer is a hand-held 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 setups and device status. The unit runs on three AA batteries and includes an external power jack. It also sports an auto shut-off feature.

The unit has XLR, RCA and optical inputs; the latter accepts 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 the 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. Cleaning the machine's 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. In the two DAT examples, both decks expected the sample-rate status flag to concur with the transmitted sample rate. Figure 1 shows a side-by-side comparison of a Technics CD player (left) and the Masterlink, respective examples of consumer and professional formats.

Note the “FS no ID,” which indicates that the sample-rate flag had not been set. In this snapshot, the Masterlink is also transmitting at 88.2kHz, but not at the time of the DAT trouble. By not setting the sample-rate flag, the Masterlink did not comply with the specification, a problem that was remedied in later production units.

Heads up

Figure 1. Half of page one (of three) channel-status pages comparing the output of a Technics CD player (left) to an early version of the Alesis Masterlink. The screen highlight is for clarity.

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 an immediate, obvious error with other equipment. In Figure 1 the rectangle to the right of OPTICAL (optical) is clear, indicating good data. In Figure 2 (from a PCM R500), the rectangle is solid black, indicating bad data, which was not bad enough to mute the audio.

The Digilyzer is a powerful tool if you know where to look. Whether the data is good, bad or out of compliance, the unit 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. In conjunction with the NTI Minirator or any low-distortion oscillator, the Digilyzer can measure distortion and provide a clue as to the cause of the problem.

Creating the tests

For most of the tests, the Digilyzer was a destination on a digital router, hence the optical indication on the display, even though many sources were tested.

Note also that the number in the center square on Figure 2 indicates the page number. There are three pages to check channel status, plus a bit-status page.

With additional reading (via manual and online) and testing, the unit becomes an even more valuable tool. It doesn't blare 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. The signal-quality rectangle, pointed out earlier, is an easy indicator of a problem that may be diagnosed on another page.

The Digilyzer saves time and speculation. From 16 bits to 24 bits, 32kHz to 96kHz, the Digilyzer tells you the good, the bad and the ugly.

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