INSIDE TRACKNTI 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 ofLine Up I had the pleasure of getting toknow its digital brother, the Digirator DR2
digital test generator. In terms of layout andpresentation 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 theMR-PRO, these keys provide direct access tothe various test signals, their signal level andfrequency (where appropriate). The rotary
wheel is used for navigation around theLCD screen and the adjustment of settings,
with the enter button selecting the requiredfunction.
The Digirator provides outputs for bothprofessional and consumer digital formats.
Connectors include an XLR-3M for AES3, acoaxial (RCA) connector for 75 ohm
S/PDIF, and an optical connector for
TOSlink stereo and ADAT eight-channelsignals. Additional connectors include a USBport, an external power supply jack, and anXLR-3F connector which accepts asynchronising input for AES3, word clockand video. The XLR and coaxial outputs aretransformer-isolated in order to be earth-free
and will tolerate phantom power withoutdamage. For further flexibility, an RCA toBNC 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.

AOverview

The menu structure and the way functions
are accessed is exactly the same as for theanalogue Minirator, but obviously with theappropriately specialised digital parameters.
Taking a closer look at the menu bar at thetop of the screen, the drop-down menu
starts with the test signal Generator settings,
followed by the ‘Transparancy’ and I/ODelay measurement functions. The lastmenu 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), afrequency sweep, a ‘Chirp’ (for impulsetests), a delay test (used in conjunction with
the NTI Acoustilyzer tomeasure acoustic delay
Dolby and DTS surround test signals cantimes), pink noise,
be generated
white noise, a sawtooth test signal formeasuring 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), samplerate (32 to 192kHz), and ‘Sync’ status (thelatter being the internal or an external
clock, with automatic detection of AES3 or
AES11, Word Clock, Video B&B – PAL orNTSC). A numeric value shows thesampling rate of the test signal.
Also included in these parameter lists atthe bottom of the screen are icons whichindicate the Channel Status (Pro orConsumer), 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 thesampling rate (ie: four channels at double
rates and two channels at quad rates).

Measurements
Besides being a test signal generator, theDigirator also incorporates a range ofmeasurement functions, including anassessment of ‘transparency’– or digital
integrity – of a system, and the I/O latencyor delay (either in milliseconds or TVframes). In the case of unequal delay times
for the A and B channels, these aredisplayed alternately.

Surround Tests
The unexpected test signal formats arethose 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

channel identification for L-C-R-Rs-Ls plus a
400Hz tone, vocal channel identification for
the LFE plus an 80Hz tone, full bandwidthpink noise at -20dBFS for the five mainchannels plus band-limited pink noise of 20120Hz for the LFE channel. There are alsopolarity test signals for all channels, sine
wave tones at 80Hz, 400Hz, 1kHz and10kHz, and a reference voiceannouncement on all channels at -20dBFS.
These same test signals are also
provided in a range of compression levels
including Dolby Digital 5.1 at 448kbit/s,
Dolby E 5.1 with 16 and 20 bit
wordlengths, and Dolby E 5.1+2 at 20 bits.
In the DTS 5.1 format, the test signals canbe produced at 754.5 or 1509 kbit/s.
A complete digital signal path bittransparency test can be performed

However, due to the limited capacity of
the unit’s flash memory, not all of theseDolby and DTS test signals can be stored
simultaneously – they are all provided on a
supplied CD, and can be loaded and stored
as appropriate via the USB interface andsupplied software. In addition, Dolby Digital
Plus and DTS High Resolution Audio test
signals are in preparation, and will beavailable for download in the near future.

Conclusion
The NTI DR2 Digirator is a little jewel of atest instrument. It is easy and intuitive touse, and also provides a useful education forsome of those hazy points of digital audio!
The flexibility of a wide range of test
signals, particularly those in Dolby Digital,Dolby E, Pro Logic II and DTS, makes it anideal source for testing signal chains as wellas general troubleshooting and verifications.
Highly recommended!

Contacts and Prices
NTI Digirator DR2
Price: £812.65(Excluding VAT)
www.nti-audio.com
Bryant Broadcast
Tel: +44 (0)20 8404 4050
www.bryant-broadcast.co.uk