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Covert Recorders Nagra JBR → DSP-1 →
Precision miniature tape recorder
The Nagra SN was a high-precision
minature audio tape recorder
built by Nagra-Kudelski
in Cheseaux-sur-Lausanne (Switzerland) from 1970 onwards.
It was based on a prototype from the early 1960s
and was built to the highest possible Swiss standards.
During the Cold War, the Nagra SN was popular at either side
of the Iron Curtain:
both the CIA
and the Stasi loved it.
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As the device measures only 14.5 x 10 x 2.6 cm,
it could easily be hidden under a person's clothing,
making it the ideal companion for inconspicuous (covert) recordings.
The image on the right shows a typical Nagra SN recorder of which the
protective lid has been romoved.
The audio quality of the SN, that records onto narrow
3.81 mm wide tape, is unparalleled.
Furthermore, the quartz driven capstan drive motor is so stable,
that the recorder is suitable for the film-making
business. A special pilot system keeps the audio in-sync with the film.
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The body of the recorder is milled out of a solid block of light metal alloy
and all components are created with the finest eye for detail.
Because of its extreme stability, its superb audio quality and unrivalled mechanical
reliability, the Nagra SN became the preferred recording machine for many
law enforcement agencies around the world and for the intelligence community at large.
It was used numerous times in the motion picture business,
both on-screen and as a production tool.
The letters 'SN' stand for Série Noir (Black Series) as the recorder
was originally ordered by US President John F. Kennedy for use by the American
secret services [2].
According to the Nagra website, the SN was even taken to the moon on one
of the Apollo missions in the early 1970s [2].
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In 1972, the SN was followed by the Nagra SNS, which featured half-track
and slow-speed, making it more suitable for covert recording of a conversation.
Because of the extended recording time, it became a standard
tool for many law enforcement agencies and intelligence services.
Due to the limited size of the device, there was no mechanism to rewind
the tape automatically as with later recorders. Instead, the operator had
to fold-out a small crank that is located at the top center,
and wind the tape back manually. The image on the right shows how
it was done.
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First, the recorder has to be placed in REWIND mode, by
pulling-out the operation lever
at the bottom left and pushing it up a little,
so that it is locked in place. This uncouples the mechanism.
Next, unlock the rewind crank by pushing-in the
horizontal grey knob at the top and
erect the small pin at the center of the crank.
You may now rewind the tape by
moving the crank clockwise.
For many years, the SN was Nagra's flagship for the law enforcement
community, but also for the motion picture industry (film) as it was
small enough to be hidden on the actor's body.
The Nagra SN was succeeded in 1984 by the
much smaller Nagra JBR,
but was kept in production until after 2000.
Over the years, more than 15,000 units were sold [5].
Furthermore, existing Nagra SN and
other models are still being
serviced by authorised Nagra service centers to this day (2019) [5].
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Year
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Model
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Description
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Speed 2
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1960
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SN
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Serie Noir (prototype)
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?
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1970
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SNN
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Mono full-track
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9.5 + 4.75 cm/s
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·
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SNN-2
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Thicker chassis (1.5 mm instead of 1 mm)
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·
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·
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SNN-3
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Improved control and reliability
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·
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1972
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SNS
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Mono half-track
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4.75 + 2.38 cm/s
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·
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SNS-2
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Thicker chassis (1.5 mm instead of 1 mm)
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·
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·
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SNS-3
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Improved control and reliability
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·
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1973
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SNG
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Mono half-track HiFi 1
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4.75 + 2.38 cm/s
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1977
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SNST
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Stereo 170-5000 Hz
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2.38 cm/s
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1999
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SNST-R
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Stereo HiFi 50-15000 kHz
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9.5 cm/s
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Version with full frequency response.
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Specifications supplied by Günter Hütter [4].
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The image below shows a top view of the Nagra SN. The leftmost reel
is the so-called supply reel. The tape is fed from the supply reel,
over the tape guide and the tension arm, along the three heads:
first the (black) erase head, then the recording head and finally
the play-back head.
When no microphone or line input is connected, the Nagra SN acts
as a play-back device. Turning the recorder ON by pushing-in the
operation lever, will start play-back. If a suitable microphone or
line input is connected to the rightmost green socket at the left,
pressing the operation lever will cause the Nagra SN to start recording.
Any previous recording will be erased first.
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Loading a fresh tape onto the Nagra SN is pretty straightforward
and is similar to loading tape on a domestic tape recorder.
Place an empty reel on the axle at the right. It will be used as
the take-up reel. The reel should be locked by rotating the knob at
the centre about 90 degrees clockwise.
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The Nagra SN was originally supplied in a black rectangular
storage cassette that measures approx. xx x xxx x xxx cm.
Inside the case
is a padded area for the recorder, the
microphone,
the remote control unit
and spare batteries.
The operator's manual
is usually stored behind a panel in the top lid of the case.
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Althoug the Nagra SN was primarily intended for covertly recording
conversations, the unit was also capable of playing back a recorded session.
Normally, when playing back, the a pair of headphones had to be connected to
the 3 mm jack sockets at the rear left.
In order to play back the sound in, say, a room, Nagra developed the special
DSP-1 amplifier
in the late 1970s. It was battery-powered and was connected
to the phones socket of the Nagra SN.
➤ More information
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The interior of the Nagra SN can be accessed by loosing the
three large bolts
at the sides of the device and pulling away the rear shell
of the case. The interior of the recorder
will now be visible. It consists of seven small high-quality PCBs,
that all have their solder side facing upwards.
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The image on the right shows a bottom view of the Nagra SN after the
case shell has been removed. At the bottom right at the two 1.5V penlight
batteries that power the machine. At the top right is the
rear of the modulation meter.
The large circular metal unit to the left of the meter
is the slim-line motor that drives the unit.
Further details in the images below.
The block diagram, that is printed
inside the bottom case shell, should explain how the unit works.
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The success of the Nagra SN recorder did not go unnoticed.
Around 1987, the design was copied by the
Soviet Union (USSR) for use
by Cold War
intelligence services like the GRU,
the KGB
and the Ministry of Internal Affairs
(MVD). The device was made by the Special Machinery Factory in Kiev (Ukraine)
and its exterior is a near-exact clone of the Nagra SN, except for
the meter.
Internally, the device is completely different however, as it was made
with special integrated circuits from USSR production.
➤ More information
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- Nagra SN, Operating Instructions. Mode d'emploi
User Manual (English/French). Code No 20.20.002.153.
Nagra Kudelski SA. Date unknown.
- Nagra SN leaflet
Nagra Kudelski SA. Date unknown. 4 pages.
- Nagra SN brochure
Nagra Kudelski SA. Date unknown. 8 pages.
- Preisliste für Miniatur-Tonbandgerät SN und Zubehör
Price list of Nagra SN recorder and accessories (German).
Austerlitz Electronic GmbH. 12 December 1970.
- Nagra SN, Set of Schematics
Nagra Kudelski SA. 12 May 1971.
- Nagra SN, Spare Parts
Nagra Kudelski SA. 1 October 1975.
- Nagra SN, Service Manual
Nagra Kudelski SA. October 1983.
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© Crypto Museum. Created: Sunday 25 March 2012. Last changed: Friday, 08 January 2021 - 16:16 CET.
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