Test Report of NTIs
Minirator MR-PROThesuccessor

Miniratorofthefamily

justarrived on the shelf*…The
tested MR-PRO has a little(andcheaperbrother)named MR2. A high value
generator for all audio
tests in the field. It’s not
an improved MR1 but atotally new design making
it a perfect companion for
the ML1 and AL1. The DR2
as digital version is alsoavailable! Check it out!

Functions* Since the writing of the article, lotof things happened in the life of theMinirator MR-PRO. Due to its digitalmanagement, it has been updated. Thereport was carried out with the firstrelease of the firmware…

On the first MR version, (it wasa Neutrik) the 2 lines LCD wereassociated with only 3 keys.
This ergonomics was not reallyconvenient. We have now a big
screen with white back light, 8 keys
and a bi-directional wheel replace
the keys. More this wheel is speed
sensitive. The back light switches off

For Who? For What?
MR-PRO is the tool you must havewhen you install or verify audio
systems, diagnosis to write if you
work in audio electronic or acoustic.
It’s also a small laboratory generator
usable to expertise defective itemswith two associates: the oscilloscope

automatically, and lights on the very
readable screen every time we hit akey. The access to all the parameteris made on the wheel by scrolling in
the menus. We found here the ML1and AL1 way. Once the parameter
highlighted, one hit on the center
key and the parameter value can be
adjusted with the wheel. When you

Innovationand of course the ML1 and AL1. Its
performances have followed theevolution of the products of themarket and its esthetic is younger.
Put in your toolbox but take care ofsmall signals!

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MR1 was innovating, the MR-PRO
brings more with its .WAV file reader
and a high resolution tuning of leveland frequency.

Test Report of NTIs
Minirator MR-PRO
12

1: NTI puts shortcuts keys to access towaveform, level and frequency screens.
The rotating ring chooses parametersand values. NTI adds a mute key. Very
convenient and nice ergonomics!
2: Unusual connectors for a generator.
We can go in on a XLR-F connector
to test cables, the USB port is used toupdate the generator, manage .wav
files, which you can play instead of sineor other shaped waves.

have to process to repetitive tasks,
10 memories allow you to presetsettings. The cherry on the cake isthe presence of three keys for an
instant access to wave, level andfrequency screens. In this step, we
have the choice of setting steps, 1 or
0.1 dB for the level (far better thanthe 2 dB of the MR1) and four steps
in fraction of octave for frequency.
NTI sets the output level from–80 to +18 dBu for sine waves, acompatible level with ML1. Generally,an audio input circuit accepts a+20 dBu (7,75V) level, +18 dBu
is an improvement on the MR1’s+6 dBu. If the MR-PRO is mainly afield generator, it’s THD as low as–96 dB (0,0016 %) at +18 dBumakes of it a perfect lab instrument.
Among the waves, we found thesawtooth wave for polarity test
(suitable for the ML1 & AL1) andthe white and pink noises. Theiroutput level is limited to +8 dBu but
you must remind that the peak leveldrives the signal close to clipping. As
the generation of signals is digital,
the maximum level is fixed byoccupation of all bits…
NTI adds a sweep generator
synchronized with ML1 plotter
or other rapid test systems. USB
MiniLINK option can then extract
the data for export in Excel. If on
the MR1 the smallest step was 1/3
octave, we have here a Hz resolution
from 10 to 9999 Hz then 10 Hz up
to 20 kHz. This limit is fixed by theShannon theorem, with the internal
sampling frequency of 48 kHz, it’sdifficult to generate clean signals
over 20 kHz.
NTI has the great idea to suppress thesquare wave! A perfect square wave
has a lot of harmonics. We needaround 10 to have a good shape on
the scope. If we need a 5 kHz squarewave, with a 48 kHz sampling
frequency, we will reproduce only
3rd harmonic. It may only be useful
to have low frequency square wave.
A bad square generated can drive tofalse interpretation. If you need areal square wave, the analog domain
is the best and it’s not difficult tobuild your generator. One way togenerate a better square wave
would have been the use of the DSD
1 bit part of the DA converter.
MR-PRO has another sweep
generator. It generates chirps,
which are continuous sweeps ofthe spectrum. The screen allows
you to program its duration andfrequency limits. You can also havea linear or logarithmic frequency
progression according to the chosen
analyzer. We regret the absence

USE
Congratulation for the ergonomics, which is far more nicethan the previous one. Testers
are integrated and shortcuts
very convenient and useful.

PERFORMANCESThe MR-PRO is tuned on the ML1and has even performances goingfurther than ML1’s possibilities.

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QUALITY/PRICE RATIO
Swiss quality and precision.
There is a price for performances.
It’s more expensive than theMR1 but is also more complete,performing and nice. A positiveassessment!

Test Report of NTIs
Minirator MR-PRO
3: NTI has a Cable Test Adapter used totest cables. On this screen we can see
the value of its two resistors. Thus you
can test a very long cable. Impedanceand balance are shown on this screen.
4: With sweep and chirp mode, you
can select a lot of parameter. Here: 1/3
oct sweep, 0.5 s per step, and 1 second
start signal.
5: A flash memory, a microcontroller,
converters, op amps are surface
mounted on a very thick and strong PCboard.

of a starting tone useful for someplotters. If you need square waves,
you can download the file fromthe NTI website in the internal
32 MB flash memory. The files have a
16 bits/48 kHz format. The capacityof the memory allows 5 minute ofrecording. Fortunately, we can loop
the samples.
To download an audio file, you’ll345each pin. With this data, we candiscover a wrong connection or finda pin where the impedance is higher
to avoid the overload of a weaksource.
Really the MR-PRO measures also
the phantom power voltage. You
may have some surprises! Here,the generator gives the voltage forthe two pins, in case of a broken orwrong circuit.
The MR-PRO has a cable tester inside.
You connect the XLR cable between
the two XLR sockets, one M one F
and the screen say the results. If
the two end are not available, NTI
has an end plug equipped withtwo resistors of different values. Ifthe cable is crossed or if there is anintrusive serial resistor, the screen
will show it.
The MR-PRO is powered with 3 AAcells. You can use the high capacity
Ni-mh cells available today theautonomy will be the same as thebattery one. The only problem isthat the available fast chargers loadcells by two or four. The autonomy
will be around some hours, it may beinteresting to use an external power
supply but NTI doesn’t give thepinout in the manual. The center pin

have to connect the MR to a PC via
USB port. The MR-PRO becomes thenan external memory. The memory is
also used to store configurations.
Furthermore, the MR-PRO canmeasure some parameters of theinput where it’s connected. Withinsome seconds, it measures the input
impedance and tests the balancingof the input reporting the value on
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Test Report of NTIs
Minirator MR-PRO
6: A reassuring word: it’s OK. The cable
is not crossed and there is no phantom
voltage. More, the MR-PRO measurespermanently the input impedance.
7: A small comparison to end: The newmodel is far sexier than the old one.
Isn’t it?

67is +. You’ll need a 5-7 V, 1000mAhpower supply. Often, the DC input isprotected against polarity inversion.

necessary to output +18 dBu from
4,5 volts or less battery. Of course,
we have the high standard of quality
ever met on NTI products.

microphone input, their value is oneof the smallest in audio, generally
more than 1500 ohms.
Level decreases to –80 dBu, theaccording dynamic is 98 dB. Takecare! We are here speaking of a 2020k bandwidth signal but the output
contains a lot of high frequencycomponents and at a low level, thesecomponent may disturb the circuits.
Oscillogram A shows the shape ofthe signal were we perceive residualand quantification noises. As the lowlevel is digitally generated, not byattenuator, we measure the HF noiseof the converter. Our advice is touse a passive low out impedance 40dB attenuator, the Minirator -40dB
Adapter, and to use it for low level
test signals. Oscillogram B showsthat our –80 dBu signal is far betterand usable! The drawback is that weDesignOne PC board, between twomolded ABS shells receive all thecomponents, LCD display included,connected with it’s flexible circuit.
Everything is managed by an Atmelmicrocontroller with a 256 kB flash
memory and an USB interface inside.
An external flash memory is added.
Signals are generated in the digitalworld perhaps with wave tables. A
PCM 1791 is used as DA converter.
Another converter, AD type, is used
for impedance and phantom voltage
measurements. Output amp is basedon low distortion CMOS opamps.
An internal switch mode power
supply delivers the high voltage

Measurements:

Measurements
The MR-PRO takes 180 to 470
mAmps
fromthebatteries,depending of the audio output
level. At 0 dBu, we measured 220
mAmps, 250 at +10 then it goes upvery fast. At this level the icon of thebattery comes quite fast! We can
add the 40 mAmps of the display
lighting, it takes around 20 % of thetotal energy!
Level indication is very precise anddue to the low internal impedance
doesn’t vary a lot with the load. On
600 ohms, we lost only 0.2 dB, lessthan a dB cut in four parts!
On the field, the Minirator will meetBA

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Oscillogram A: The output level of thegenerator is –60 dBu. The lower trace istaken trough a 10 Hz-500 kHz BW filter.
The upper trace shows the same signal
in a 20 Hz- 20 kHz band.
Oscillogram B: For this experiment,
the output level of the generator is–20 dB and we inserted a 40 dB pad.
The measurements are made in the A
conditions. The lower trace is clean!

Test Report of NTIs
Minirator MR-PRO

loose the impedance measurement.
The measurement of the signal level
at –80 dB gives –60 with a 500 kHz
bandwidth but with a 22 kHz BWfilter, we recover the –80 dB.
The below table gives the evolutionof THD+N vs level measured with an
Audio Precision System One and on
the NTI ML1. Measurement is madewith a 22 kHz BW filter, the same
applied internally to the ML1 due
to its digital process. Of course, theincreasing of the THD is principally
due to the floor noise. If you workwith a very low level, a good analog
oscilloscope will be a good tool tolook at the signal shape. Of course
if you use an attenuator, the THD
will be lower, if the attenuator isfrequency linear.
When the Minirator goes into
mute, the output signal is–93 dBu unweighted and –96 dBu
A-weighted. The dynamic of theconverter is 112 dB.
We have connected the MR-PRO
to our Windows 2000 PC’s USB
interface. No problem! The behaviorof the generator is then a memory
and it’s not powered by the USBlink. We like Ergonomics, play of.wav files, high performances,integrated cable tester, impedance
measurement, portability and totalcompatibility with ML1 and AL1.
We regret digital noise, small flash
memory and consumption.

Minirator MR-2
The MR2 is a light and cheaperversion. No preset memories, no.wav file play. The testers for cable,
impedance and voltage are omitted.
The output level looses 10 dB, theoutput impedance grows to 200
ohms and the THD looses 6 dB due
to the increased noise level.

Digirator DR-2
Knowing the digital way of building
signals in this 2nd generation of signal
generators, it would have beeninteresting to have a digital output
with a perfect –98 dB signal… NTI
offers a specific generator whichadds to the Minirator signals DTS,
Dolby Digital and Dolby E signals,
synchronizes the generator on
various sources, gives status channel
data, tests the transparency of a nonlinear modulation and measuresdelay. Its sampling frequency goesup to 192 kHz on XLR and RCA, 96
on optical output and 48 for ADAT.
The maximum resolution is 24 bits.
The Digirator DR2 available sinceApril 2008 and is totally compatible
with the Digilyzer DL1.
This article is the translated Minirator
MR-PRO test report, as printed in theSono magazine, edition January 08. Thespecifications have been updated.
Text & Photos: Etienne Lemery
Translation: Etienne Lemery

Table: THD+N vs output level measured with AP System One and Minilyzer.

Technical Specifications:Outputs
Balanced XLR, unbalanced RCA
phantom power resistant, 12.5
Ohm balanced, Imax = 10 mA

InputsDC power supply, USB
XLR for cable test
Signal Wave Forms
Sine, Pink Noise, White Noise,
Polarity test signal, Delay test
signalContinuous Sweep
Linear / Logarithmic
Frequency setting
10 Hz - 20 kHz
Output Level Ranges- 80 dBu to +18 dBu
THD+N-96 dB (0.0016 %) @ 18 dBuNoise Floor typ. 15 μV
Impedance Measurement
Absolute value Z
4 Ohm - 50 kOhm balanced
Power Calculation
25 V, 50 V, 70.7 V, 100 V
Phantom Power Reading
0 - 54 V
Flash Memory
32 MByte, for storing wave files
and configurations
USB Functionality
Firmware update, Mass Storage
Battery Life: typical : 10 h
Weight including batteries
310 g (11 oz.)
Dimensions (LxWxH)
152 x 81 x 43 mm incl. jacket

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