Tandberg 11 Review

Page 1

TANDBERG MODEL 11. TAPE RECORDER

O lint many )trtrs, wrtually all ne\\'ton1ponents coming to
us for test haVe heen stereo tnndels. In the (use of tape re-
tordurs, nmnu models are still \ery much on the scene, but
llte) are almost never meant for serious listening or pro
lessionitl use. An impressive exception to this rule is the
new Tlmdberg Model 1!, a professionaltquality portable
mom) reeercel recurder.

The Mndel II is lully transistorized, and tan be operated
{tom KI selfreontained battery park from which it draus 3
to 3 watts. If ordinary dry1 (Clix are used (ten Lid-oh D
cells are required), the battery lite is about 5 tr) 6 hours in
continuous operation, or about 20 hours if the machine is
used half an hour per dity. Rechargeable melt cadmium
cells can also he used for long-term economy. For a. ' -hne
Operation. Tandberg provides an optional battery eliminzb
Ior that physieally replaces the internal battery pack. it (an
also be used externally to rathai'ge nickel-Cadmium lwatrerr
ies in the remrder through an areessory tunneetnt'. \V'e
lesled the Model ll with the 11 e [unset supply installed.

This is a halt-track machine that [aims flinch reels. [I has
three heads and separate i'emrding and playback eleetitmits
tor oft-thetape monitoring \xhile recording. The miern»
phune input, for a ZOO-ohm balanced dynamic microphone,
uses a locking prntessional-type conneemr. Two line inputs
are Provided. for high and low-lewl signals. Separate re-
cordingrlcvel controls for the miemphone and line inputs
make it possible to mix signal Suurecs.

There are two playback output: using miniature phone
lacks. One is a monitoring output {or 2004)th unhnlA
anced headphones; the other is :\ (IUO'OlHI! b" laneed output.
Both are controlled by a single [Vittylfiilt'lvkfl'fil control. A
small built-in speaker L'lHI be swttched on to monitor either
incoming nr outgning signals. but the line outputs are dis-
t'onnected when the speaker is on. A meter indicates rc-
eording lEVel, and when the Imi button is depressed, it
indicates the level at the line output. A battery-test button
switches the meter to check the condition of the batteries.

The tape-transport cnntml is a single leVer that provides
fast-forward and reVerse When pushed tight or left: nor-
mal speed is obtained by pushing it up. A separate record
hie-interlock button must be pressed simultaneously tu
record, The stop lever starts and stops the tape instantly
without rausung the machine to switch out of the record
mode.

The three operating speeds of 1%, 35A, and 71: ips
are selected hy a rotary switch that sets the unique elec-
tronic speed-control circuits of the Model H. Precise and
mnststent speed is a necessity [or professional applicatmns,
and since when operating on batteries there IS no at. power
lint: to establish the motor speed, a very effective elec-
tronic substitute was developed by Tanrlberg engineers.

(Curl/maul on page 44)

STEREO REVIEV.

Page 2

A thlttIHtulL. \\llLLi UH the tapslan dme slirttt generates
an :l.tr \ottayc |lt it special piLLup head This voltage is
.tmplitied. clipped. and then deltcted in a ratio detector
whose dc output is pruportinnal t0 the ttt-qtiency or to
the motor speed. The output of .i scpamtv Ztl-kHz square-
\\;t\-e gentramr is integrated to produce .l triangular wave
shape which is summed with the da. output of the ratio

iiiiiifa:

detector, The summed voltage controls a Schmitt-trigger
cittutt, the output of which is a series of 20~kHz pulses
whose width is a function of the motor speed The average
value of these pulses, after filtering. is a dc. voltage whose
valuc is .1 function of motor speed After amplification, it
drives the d.c.operated capstanalrivu mutur.

This system maintains an extremelv accurate motor
sptcd, since any tendency for the speed to change produces
a corresponding compensating change in the that operates the motor. For speed change, the tuning of the
ratio detector is changed. and the motor speed then changes
accordingly to maintain a balanced condition.

\t'r'e tested the Tandherg Model 1! with 3M type 150
tape, for which it had been adjusted, lts performancc was
well ithin specifications, and was of a fully professional
caliber. At 71/: ips, the overall retold-playback frequency
response w :15 dlt from 55 to 30.000 H2, and the

NAB playlutck frequency response as :0 ) dli hunt fit)
to 15,000 Hz The unweighted signal-rovnoirc ratio was 60
dB. Wow and flutter were measured as (L05 and 0.09 per
cent. resPectivcly.

At 3% ips, the rccnrd-playlurk response was ills dB
from 50 to 12,500 Hz. and the NAB playback response
was :04 dB from 50 to 7,800 Hz. The signalrtornnise
ratio was 59 dB, and wow and flutter were 0.05 and 0,1 per
cent The 13,-ips speed produced very listenalile quality,
although with a somewhat restricted frequency response
of :2 dB from 40 to 6.300 Hz. The signal-to-noise ratio
was about thc same as it was for 3% ips.

The HIGH line input required .12 volt, and the LOW re
quired 3.4 millivolts fur lLdB recording level. At 0 dB.
the overall distortion wrts 2t-t per cent. drupping to less
than l per cent at 10 dB, The maximum line output
before clipping was 5.3 volts. In wind and rewind. about
2 minutes were required to handle 1.200 feet of tapci Th:
normal operating speeds were exact, as determined by a
tape SNOltOSCOpC.

The Mndc] 11 is probably nnt [or the casual hobbyist,
but should he an excellent choice for recording interviews
for broadcast (the builtrin suitchahlu automatic level con-
[:01 Will be useful) or othcr field operations where the
weight and bulk of ctmxctttmnal prufussional rctordcrs
would be ptoltihitive. Its performance, both mechanical
and electrical, leaves nothing to he desired for such ap-
plications. The unit measures 4 x [0 x 13 inchts and
weighs 12.1 pounds with batteries.

The Tandhtrg Model It sells for $449.50. A fullrtrnck
unit and a pilot-tone version for motion-picture sound
synchrrmizers arc also available. The optional a.c. power
supply is Slit, and a leather carrying case with shoul-
der strap is $29.95.

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