NTI Digirator DR20 pages

INSIDE TRACK

NTI Digirator DR2
Terry Nelson MIBS reviews a new digital test signal generator.

fter reviewing the NTI Minirator
MR-PRO analogue signal test
generator in the previous edition of
Line Up I had the pleasure of getting to
know its digital brother, the Digirator DR2
digital test generator. In terms of layout and
presentation the two units are identical,
incorporating a large LCD screen, central
rotary wheel, with enter key, four function
keys (escape – wave – level – frequency),
sensitivity and mute keys, plus a combined
on-off and backlight button. As with the
MR-PRO, these keys provide direct access to
the various test signals, their signal level and
frequency (where appropriate). The rotary
wheel is used for navigation around the
LCD screen and the adjustment of settings,
with the enter button selecting the required
function.
The Digirator provides outputs for both
professional and consumer digital formats.
Connectors include an XLR-3M for AES3, a
coaxial (RCA) connector for 75 ohm
S/PDIF, and an optical connector for
TOSlink stereo and ADAT eight-channel
signals. Additional connectors include a USB
port, an external power supply jack, and an
XLR-3F connector which accepts a
synchronising input for AES3, word clock
and video. The XLR and coaxial outputs are
transformer-isolated in order to be earth-free
and will tolerate phantom power without
damage. For further flexibility, an RCA to
BNC adapter is provided to cater for AES-3id
format test signals, and an XLR-3M to BNC
adapter does the same for a sync reference
signals.

A

Overview

The menu structure and the way functions
are accessed is exactly the same as for the
analogue Minirator, but obviously with the
appropriately specialised digital parameters.
Taking a closer look at the menu bar at the
top of the screen, the drop-down menu
starts with the test signal Generator settings,
followed by the ‘Transparancy’ and I/O
Delay measurement functions. The last
menu option is labelled System which
provides access to the unit’s serial number
and firmware issue, plus various parameters
for power saving and the screen backlight.
Selecting the Generator menu provides
access to ten test signals: a sine wave
(adjustable level and frequency), a
frequency sweep, a ‘Chirp’ (for impulse
tests), a delay test (used in conjunction with
the NTI Acoustilyzer to
measure acoustic delay
Dolby and DTS surround test signals can
times), pink noise,
be generated
white noise, a sawtooth test signal for
measuring signal
polarity, a user-loaded
wave file, and finally,
various Dolby Digital,
Dolby E and DTS
encoded test signals.
There are also facilities
via the ‘Config’ menu
for storing and recalling
test signals and files,

and for muting either
stereo channel or inverting
the polarity of the right channel
relative to the left one.
The bottom of the LCD screen displays
the various digital parameters affecting
the test signal, such as selected
impedance (Hi-Z, 75 or 110 Ohms), sample
rate (32 to 192kHz), and ‘Sync’ status (the
latter being the internal or an external
clock, with automatic detection of AES3 or
AES11, Word Clock, Video B&B – PAL or
NTSC). A numeric value shows the
sampling rate of the test signal.
Also included in these parameter lists at
the bottom of the screen are icons which
indicate the Channel Status (Pro or
Consumer), whether linear or non-linear
(data reduced) PCM signals are being used,
and the presence of 15/50 pre-emphasis.
The selected optical output status is also
shown here (two-channel stereo, ADAT
eight-channel and Off). In ADAT mode,
the number of channels is linked to the
sampling rate (ie: four channels at double
rates and two channels at quad rates).

Measurements
Besides being a test signal generator, the
Digirator also incorporates a range of
measurement functions, including an
assessment of ‘transparency’– or digital
integrity – of a system, and the I/O latency
or delay (either in milliseconds or TV
frames). In the case of unequal delay times
for the A and B channels, these are
displayed alternately.

Surround Tests
The unexpected test signal formats are
those for Dolby Pro Logic II, Dolby Digital,
Dolby E and DTS, all with a fixed 48kHz
sample rate. The full set of Dolby/DTS
signals for the Digirator consist of vocal