Nagra 3 brochure

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KUDELSKI - PAUDEX-LAUSANNE - SWITZERLAND

A NEW ADDITION TO THE LINE OF NAGRA Ill ACCESSORIES

THE DH SELF-CONTAINED SPEAKER-AMPLIFIER

THE COMPLETE UNIT

This is an accessory which consists of a light alloy box. containing an amplifier, a high
efficiency speaker and 12 1.5 V flashlight batteries.

By connecting this unit to the line output. or monitoring output of the Nagra Ill. one can
listen to a prerecorded tape, or monitor a recording. at a level and quality similar to that of a
small Hl-Fl installation.

During recording, one can monitor the sound either from the play-back amplifier, or from
the recording amplifier, thus comparing the sound before and after recording. Provided of course.
that the microphone is not within pick-up range of the speaker.

One can also by-pass the incorporated speaker, and connect the amplifier directly to an
external loud-speaker (impedance 3-7 ohms).

THE AMPLIFIER

This is a pure class B' amplifier. It is of very advanced conception. and can be consid-
ered as perfect, in comparison to the other components of the DH. The basic circuitry of this
amplifier. has been developed by our engineers. some years ago, but it is only now that the pro-
gress in electronic components, enables us to produce it, with the level of quality and reliabilv
ity that we are accustomed to.

Although a class B' amplifier. it has a fidelity rarely achieved even by the best existing
amplifiers of this class. This high performance, is achieved by the very conception by which the
amplifier is constructed, and not by delicate adjustments and balancing. There is nothing critical
in the construction, and the amplifier will give excellent performance over a wide range of tem-
peratures and power supply tensions.

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POWER CONSUMPTION

As it is a class 8' design, the power consumption, with no signal, is only 2 mA (1 mA is
taken by the voltmeter which measures the batteries tension). Generally speaking, the power
consumption of the DH unit, is extremely low, compared with the maximum power output available.
This is due to the class 8' construction, in which the amplifier consumes energy in direct proportion
to the power required. Statistically, power peaks are quite rare in normal sounds.

As the impedance of the loud-speaker increases with the frequency, and as the consump-
tion decreases when the frequency increases, The efficiency of the speaker increases simultane-
ously.

SPECIFICATIONS

Dimensions: Identical with the Nagra III: 12.5><9.6><4.4 (318x244x112 mm).
Weight with batteries: 3.850 Kg.
Empty weight: 2850 Kg

Input: The DH includes an input attenuator. permitting the regulation of sound volume.
Minimum input tension for complete modulation:

A. 4,4V plus 1 to 2db reserve : 5 to 5.5 V. Input impedance between 2.5 to 4,5 Kohm resistive
impedance. for connection to the line output of the Nagra III.

B. About 200 mV 200 Ohm for connection to the monitoring output of the Nagra III.
Output: Either with the incorporated speaker. or with an external load.
Maximum tension, depends on the condition of the batteries. With new batteries: 52 V RMS.

The Input and the output are asymetric, and they have a common pole, which is connected
to the box. As the batteries are floating, the DH should not be powered by any outside source
having some connection with either the input or the output.

Internal Impedance: much less than 50 milliohms in all the frequency spectrum (20 to
20.000 c/s).

Permissible load: there is no critical limit. more the load is of a lower impedance, higher
the output power becomes. and consequently, the power consumption is augmented. By loading
with 1 ohm, we obtain about 25W on the output, but regular flashlight batteries, will not stand this
drain for a long time. In practice, the load on the DH is about 4 to 5 ohms, which gives maximum
power output of 5 to 6 Watts.

Frequency response curve: flat at +/- 03 db from 20 to 20.000 c/s (+/- 0,1 db on request).
Distortion: less than 0.1 "/0 up to the maximum power in all the spectrum (except at 40 c/s
: 0.3 lVa).

Transitories: There are no transformers or other reverberating elements. The transitories
are therefore perfectly transmitted.

The back ground noise of the amplifier is much less than 5 Micro-Volts in the frequency
scale considered, which gives a recession of the back ground noise to -120 db. Of course, this
is absolutely inaudible.

Functioning temperatures range: We have tested the DH in temperatures between - 23° C and
+50D C. without observing any noticeable decrease of performance. At very low temperatures, the
batteries drop in tension, and in higher temperatures, the life duration of transistors and condensers
is diminished.

Acoustical characteristics: The frequency response is acceptable from approx. 50 to 15.000
s/c (at +/- 10db).

The maximum sound level, at 1 kc, at 25 cm from the speaker. is about 110 to 115 phones.

Net user price F.O. B. Lausanne: 400.- Swiss Francs. Price is subject to change without notice.

Printed In Switzerland