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.

Have you been avoiding the plunge into the world of geek-dom? Neutrik has solved that problem once and for all by packing an arsenal of the most essential and powerful measurement tools into an affordable user-friendly package called the "Minilyzer." The "street" price at MCM $399. The ML1 is a handheld audio analyzer designed to be used at the moment an audio mystery appears — because we all know that when the technician shows up the problem will be gone...
In addition to the primary capabilities of this powerful little box — detailed in the seven major headings below — there are a handful of "little things" that make the ML1 about as audio-friendly as a piece of test equipment can be. For example, most portable and affordable test equipment is often unbalanced, a serious issue when trying to measure a balanced device under real-world conditions. The ML1 includes a balanced XLR input as well as an unbalanced RCA input. Three AA batteries supply power, automatic turn-off time is adjustable and four user presets allow the ML1 to boot into your favorite mode. There is even a headphone jack.
Of the Seven Functions, many are intermixed within the large, easy-to-read, backlit LCD screen. For example, the LCD is large enough to display LEVEL in large bold characters while simultaneously including an analog-style linear-meter at the bottom, a frequency counter in the upper left corner, plus an inspired Input Balance indicator in the upper right corner. (See heading # 5.)
NOTE: Despite the piccolo footprint, la machina (the ML1) is quite capable of getting you into trouble. Translation: It is just as easy to take a bad measurement as a good one. Please read the Sidebar: The Ultimate Test, to learn how to compile real data.

1. LEVEL
The ML1 displays the RMS value of a sine wave test signal in milliVolts (mV), as well as the relative level in dBu and dBV, referenced to 0.775volts and 1volt RMS, respectively. In addition, the ML1 has a RELATIVE mode for precise comparisons of two or more signals — Left and Right, for example — with a signal-to-noise ratio as wide as 119dB!
NOTE: For years, technicians purchased the Fluke 8060A ($479 @ www.i-mcm.com) for its ability to measure RMS volts and dBu / dBm. The Fluke doesn’t do dBV, its noise floor bottoms out @-74 dBu (compared to -99dBu for the ML1) and it’s too old to have the DSP to do ALL the sexy things that the ML1 can do. Because the Fluke is a Volt-Ohm-MilliAmp meter, however, it has no upper level limit — compared to the ML1’s 7.75volt / +20dBu ceiling. I would like to see this ceiling raised 10dB.

2. THD+N
When measuring Total Harmonic Distortion + Noise (THD+N), the "+N" infers that Noise is included as part of the measurement process. How can it not be? Unless pushing a device purposefully into the red, you hope that both distortion and any noises — hiss and hum — are way down in the sub-basement of random electron movement. The only way to easily separate distortion from noise is to use the built-in 3rd Octave analyzer. More details under 3rd Octave, heading #7.
Inside the ML1 is an A-to-D converter capable of 119 dB of dynamic resolution. The sample rate limits bandwidth (frequency response) to 20kHz, as pointed out by Neutrik in the manual. This can potentially yield different (most likely lower) readings relative to more sophisticated gear, but only when in the LINEAR (flat response) mode. Analog test equipment is not bound to the sample rate. The Hewlett Packard Model 8903B Audio Analyser, for example, has a 30kHz "window."
There are also built-in filters so that the measurement window can be "weighted" (bandwidth restricted) to include what is relevant to the test. For example, the popular A-weighted filter (as per IEC 651) is often used because it reflects the ear’s sensitivity to noise. The other filter options are C-Message (IEC 468-4), HP22 (high pass @ 22Hz), HP60 (high Pass @ 60Hz), HP400 (High Pass @ 400Hz) and a Voice-band filter. These filters are available in the Level, THD+N and 3rd Octave modes.
NOTE: Searching the IEC on the web for specifications yielded nothing, their search and destroy mechanism is about as useful as Microsoft Help and they want money for documentation I couldn’t find. If you want an IEC clue, go to heading #6: Sweep.

TESTING MY WORLD
I used the ML1 to measure the THD of two oscillators — the GTC Tone Plug and the Neutrik MR1 — and two mic preamps — a Great River transformer-less prototype and an Altec 1566 vacuum tube preamp. The Tone Plug is a handy "generator in an XLR plug" to be commended for its size, not cleanliness. Check out Table-1 for the results. While the Minirator is respectable for it’s price range, to truly measure the Great River’s performance, a better oscillator would be required. As you can see, there is almost no difference in the performance of the MR-1 alone compared to its use with the Great River preamp.

3. VU+PPM
The ML1 emulates three metering standards: mechanical VU meters (referenced to +4dBu), Type-I and "Nordic" Peak Program Meters (PPM, +6 dBu ref) and Type IIA PPM (+8dBu). The user can reconfigure all references. Both VU and PPM are simultaneously displayed. Each includes a numeric Peak Hold indicator, plus there are two Integration Time options: Normal (Type-I and Nordic: 5ms. Type-IIa: 10ms). In FAST mode, the integration time is 1 ms for all standards.
While observing the output of a Panasonic SV-3700 DAT, I immediately realized that the ML1 could use one additional metering standard capable of being calibrated to digital audio’s 0dBfs maximum. For example, the SV-3700 has a –18dBfs nominal reference, the range should should accommodate a "low" of –20 dBfs and a high of -10dBfs. Neutrik could probably turn VU+PPM into a stand-alone stereo product with both analog and digital inputs (and a larger LCD screen). It would be a helpful mastering tool to see accurate peak information while maintaining some consciousness of "Volume" as per the VU meter. The VU meter should not be solidly in the red while the PPM would be kissing 0dBfs.

4. POLARITY
The Polarity test requires both the MR1 and the ML1. The MR1 generates a pulse that is easily detected even after travelling through the air. Selecting Polarity on the ML1 engages the input select option — a choice of either the XLR / RCA connectors or the built-in microphone. It works!

5. BALANCE
Quite unexpectedly, the very first "if only" feature I thought of was an "input balance" indicator — NOT of Left and Right, as this is a MONO box — but of the incoming signals on pin2 and pin3. This feature is a reality on the ML1 putting this gizmo and me on the right foot from the very beginning. A 6dB level problem in the analog world is not uncommon — active balanced outputs can become damaged, or interrupted via dirty patch cord or bad cable — the ML1 will tell which pin isn’t doing its share of the work.
Note: The ML1 "loses" what little headroom it has if the signal is not precisely balanced. I noticed this when testing the SV-3700, whose pin2 and pin3 outputs were particularly unmatched, reducing the max headroom in this case to +19.3 dBu.

6. SWEEP
Sweep has two options, the traditional RMS Level vs Frequency or Time vs any of the following: Level, THD+N or Frequency. Getting this mode to function was most difficult and the manual was not perfectly clear (perhaps due to translation). I got results simply by copying the example in the manual. Here, a picture was worth a thousand words. The best example would be to plot THD+N to show how distortion increases with increased levels.

7. 3rd OCTAVE
The 3rd Octave analyzer can display the audible bandwidth from 20Hz to 20kHz in 31 bands. As mentioned, THD+N does not separate Distortion from Noise. "Harmonic Distortion" is a lack of sonic cleanliness relative to the input signal. Some vacuum tube gear is famous for its pleasing even-order (octave) harmonics. Input 1 kHz, for example, and push the device into its non-linear region (not hard clipping) and watch the — second harmonic (2kHz) pop up as in Figure-1.

The cursor can be moved to each of the 31 bands to confirm both frequency and amplitude, the latter in both dB and %. An opamp circuit in hard clipping will produce odd-order harmonics (square waves are made from these), the third harmonic to 1kHz is 3kHz. as in Figure-2. See the Altec preamp specs in Table-1.
The ML1 will also reveal unrelated content such as hum (fundamental and harmonics), hiss (the curve will vary with source topology, such as produced by amplifiers and analog tape recorders), plus the more common uses of spectrum analysis — the dreaded and completely frightening process of room / monitor-speaker evaluation.

8. SCOPE
If you read my article on trouble-shooting bad capacitors using square waves, the "oscilloscope-like" waveform display is the icing on the cake. Of course the perfect companion to the ML1 is the Minirator (the MR-1 is $139.95 @ www.i-mcm.com) reviewed in the ??? issue and featuring both sine and square waves. As with most LCD scopes, the ML1 does not have amazing resolution, further hampered by the 20kHz bandwidth, which softens square waves until 10kHz looks like a sine wave. That’s ok. About the cost of a cheap-but-real ‘scope alone, the ML1 is much more likely to see active duty, adding credibility to the overused phrase "bang-for-the-buck."

GOOD DADA
Reviewing the ML1 was a good brain exercise, emphasizing the relative ease of making a bad measurement compared to the work involved to acquire good data. That said, after reading this review, the people at Neutrik Test Instrumentsinformed me that an external 20dB attenuator is now available as an optional accessory.
Note-1: This will "pad" the output of the Minirator MR1 — or any oscillator — so that noise measurements would reflect the device under test and not the audio source. It can also pad the input of the Minilyzer ML1 to extend its useful input range.) Otherwise, there is only one flaw. The maximum input of the ML1 is +20dBu, which is not high enough and easily compromised if the signal balance is not perfect.
Note-2: Software updates are also available at the Neutrik Test Instruments web site.

The ML1 is small enough to be kept in a control room or clipped to a belt — for those technicians on the move who are also looking to start a fashion trend. (PDAs might suddenly become less cool!) Consider how many times you’ve returned to the scene of an audio crime only to find no suspects and no problem? Now you can whip out this nifty little "geek tri-corder" whenever a problem occurs. By creating the Minilyzer, Neutrik Test Instruments have given more people the power to troubleshoot. The more you use it, the more you’ll understand that a little science never hurt anyone.
This review was written for the December 2000 issue of MIX. In the holiday spirit, be a good geek so that you can order both an ML1 and an MR1 without guild while sitting on the Fat Guy’s Lap. (HINT: Don’t make any comments about the red suit or the funny smell coming from the beard.) Then, look forward to a happy stocking hanging from your mantle bulging with "mini-toyz" on that magic day.

I had too much fun reviewing the ML1 and I'm not giving it back!

REVIEW SUMMARY
NTI has a complete line of "expensive" test equipment of the type used by manufacturers, designers and specification certifiers. I believe in this "mini" series from NTI because they provide useful, affordable tools for users who might otherwise not purchase anything. In my goal to make technology more tangible, these tools provide the "link" between an instructive article and the curious end-user.
If, for example, I present an article on distortion, users can now do the same test, step by step with the same equipment. The satisfaction of either confirming a suspicion and finding a problem or knowing that "all systems are go" is comforting. That said, analog audio is easy to troubleshoot compared to digital audio. Learning how to troubleshoot a system and correctly use test equipment are value-added skills. That's why I am looking forward to reviewing the Digilyzer which should be an equally useful aid to unraveling the mysteries of digitized audio.

SIDEBAR: The Ultimate Test
In carpentry, the motto "Measure twice, cut once" couldn’t be more applicable than to the art of acquiring good data. Measuring NOMINAL level from a device is child’s play, but measuring signal at or into the noise floor is quite another. This is NOT a fault with the ML1. I made several attempts until finally the results were consistent. You might not think much about "impedance," but when taking measurements, both the source and the destination impedance must be addressed.
When measuring mic preamp performance at both minimum and maximum gain, the gain structure between it and the sound source (an oscillator) become quite critical. You cannot simply turn down the LEVEL at the oscillator because, in some cases, a buffer amplifier follows the Level control. The oscillator’s output amplifier has plenty of noise when looking down the high-gain barrel of a mic preamp. The top of Table-1 proves that reducing the level of the Minirator increases noise revealed in the THD+N measurement. Fortunately, the 3rd Octave analyzer helps to "see" the various noises.
I fashioned a quickie attenuator between the oscillator and the preamp using a 1kohm pot across pin2 and pin3 of the female XLR. Pin3-f was connected to pin3-m, while the wiper from the pot was connected to pin2-m. With the Great River preamp set to max gain, I adjusted the trim pot so that preamp output fell just under +20dBu (+19.9 dBu) keeping in mind the ML1’s inability to tolerate anything higher. I then checked the attenuator output (-45.7 dBu) and calculated the gain to be 65.4dB.
Once the gain was determined / confirmed, I removed the generator and attenuator and connected a source impedance that represented the average mic. I chose 150 ohms because it was used to create the preamp’s published specs. To calculate Equivalent Input Noise (EIN) = the noise floor + the gain setting. An older style signal-to-noise ratio (SN) measurement was also made. SN = the max output before clipping + the noise floor.

Audio test equipment is usually one of those luxuries that only professionals can justify. For the majority of recording musicians, the best testing and calibration tools available to them are an approximation of a sine wave from their synth and the readings from their console meters. However, Neutrik Test Instruments (originally part of the well-known connector manufacturer, but now a separate company) have produced some very neat and surprisingly affordable hand-held miniature test instruments, the Minstruments series. These currently comprise the MR1 Minirator signal generator, the ML1 Minilyser signal analyser and the MiniSPL, a calibrated measurement microphone designed for use with the ML1. There is news of a DL1 Digilyser digital audio analyser on the way, but this isn't yet available at the time of writing.

Minirator

The Minirator can produce any of a range of sine waves between 20Hz and 20kHz (in 31 third-octave steps), any of a range of square waves between 20Hz to 5kHz (in 25 steps), or a stepped sweep of sine waves from 20Hz to 20kHz (with adjustable step times from 0.05 to 5S) with an identifying 1kHz tone before each sweep. The unit also generates white and pink noise, as well as a polarity test signal of the impulse type which is used in conjunction with the Minilyser. Output level can be set anywhere between -76Bu and +6dBu in 2dB steps (accurate to 0.5dB) and the unit set to display levels as dBu, dBV or RMS voltage.
There are two outputs: an unbalanced option on a phono connector at the top of the unit, and a balanced option on a three-pin XLR at the base, which folds very neatly into the body of the unit. The unit is powered by a pair of AA cells giving around 20 hours of continuous life, and the machine can be configured to power down automatically after three, 10, 30, or 60 minutes.
Driving the machine is very intuitive, with the only controls being a Mode button and a pair of cursor keys. There are two control screens, the first of which selects the output signal type, frequency and level, while the second sets the power-down mode, the level display units and the sweep frequency step time. The Mode key is used to cycle around the various functions and the cursor keys adjust their values. Holding the Mode key depressed for about two seconds switches the power on or off.

Minilyser

The Minilyser is physically similar to the Minirator, but slightly larger and more complex. The front panel boasts a set of four cursor keys with a central Enter button, and both Escape and Power buttons. Three inputs are provided: analogue audio on a balanced XLR and an unbalanced phono connector, plus an internal microphone (used only for checking the polarity of loudspeakers). There is also a monitor output on a 3.5mm jack, with a built in compressor circuit to ensure near-constant monitoring volume.
Powered by three AA cells, the unit should operate continuously for around 16 hours, though this will depend on the mode in which the LCD screen's backlight is operating. The backlighting can be disabled or can be configured to come on for three, 10 or 60 seconds whenever the power button is pressed, and the LCD contrast can be adjusted over a wide range. Automatic power-down facilities, similar to those of the Minirator, are also provided. Four memories allow the user to store useful sets of configuration settings.
The Minilyser offers level measurement, Total Harmonic Distortion (THD) + Noise readings, VU and PPM metering, frequency detection, polarity testing, signal balancing error assessment, sweep frequency response display, third-octave spectrum analysis, and an oscilloscope. Each selected function is portrayed on the large LCD with both numeric and graphical displays. In many of the modes there are several weighting factors available -- including A and C weighting; 22Hz, 60Hz and 400Hz high-pass filtering; and a voice band-pass option -- as well as fast, slow and impulse time averaging.
Level measurements can be made in dBu, dBV or voltage, the latter either as an absolute figure, or relative to a previously established reference (in terms of dBr, percentage, or scaling factors). The VU and PPM scales can be configured for any appropriate reference and ballistics, while the distortion and noise test can be expressed in decibels or as percentages. The balanced interface 'balance error' can be given as a percentage or as a scaling factor.
The sweep mode can create a standard frequency reponse graph or graphs of level, THD + Noise or frequency against time. In the case of the frequency response mode, the unit is armed and then starts recording and displaying the graph when it detects a 1kHz or 315Hz reference signal. The graphs against time are operated manually, with the user having to input a recording period and the time between each sample. The third-octave analyser display is exactly as you would expect, with options to adjust the averaging time, and the scope display provides a very rough-and-ready approximation of the signal shape. To make life easy, the timebase and amplitude are set automatically. The polarity test, when used with the appropriate MR1 output, provides a simple 'positive' or 'negative' response, when measured either through the XLR or phono input or via the internal microphone.
The MiniSPL option wasn't provided for review, but consists of a calibrated omnidirectional electret microphone which simply plugs into the XLR socket on the Minilyser allowing it to perform a range of acoustic measurements. These include instantaneous, maximum or minimum sound pressure levels, equivalent continuous SPL (used in noise at work assessments), and spectrum analysis of speaker systems.

NTI MINSTRUMENTS
pros
Cost effective.
Fast, intuitive operation.
Battery powered
cons
No internal speaker on Minilyser.
summary
Cost-effective, portable, fast and simple signal generator and analyser tools. Effective when used together, but also useful as stand-alone units.