NAGRA III - tape recorder

NAGRA III (1957) DC servo controlled electric motor. Germanium transistors

The Nagra III is a self contained professional tape recorder, assuring an excellent reliability factor, and the best recording quality available outside your studio. The frequency response, Signal-to-Noise and wow and flutter characterisctics  of the Nagra III, are similar too those of the best studio consol recorders, but modulation noise is even better.

Motor and speed stabilizer

The motor of the Nagra is of the permanent magnet electrodynamic type and resembles a d'Arsonval galvcanometer with central magnet. The Nagra III uses a new technique for controlling the speed of the motor.

The motor carries on its spindle a phonic wheel as well as the capstan, which passes in front of a magnetic head - the tachometer head. This head is magnetised and the rotation of the phonic wheel induces an alternating current, the frequency of which depends upon the speed of rotation of the motor. This passes through the tachometer amplifier  where it is  shaped into a square wave of constant amplitude of about 6 volts peak to peak. This output is taken to a frerquency discriminator. This operates the servo amplifier which controls the motor speed. As the voltage at the servo amplifier becomes increasingly negative, so the motor current will increase.

Microphone preamplifier

This Nagra is equiped with a new type of microphone preamplifier designated LN. This preamplifier permits the selection of input impedance  between 50 Ω and 200 Ω. All that is necessary to do in order to change from one impedance to the other, is to rewire internally the connections on the input transformer.

Specifications:

Electronics:  38 Transistors, 15 Diode, 1 Zener Dode

Tape Speed:  15 ips, 7,5 ips, 3-3/4 ips

Reel Diameter:  7" with cover open, 5" with cover closed

Speed Regulation:  0,05% or better 60/50 Hz buil-in stroboscope

Rewind:  fast rewind and fast forward controls

Magnetic Heads: 

1 High frequency erase head with double gap; 

1 Full track record head; 

1 Full track playback head; 

1 Neopilot sync track head with high frequency  bias

Equalization:  NAB

Inputs:

1 x Microphone  :  50 - 200 Ω impedance

1 x Line ( 600 Ω) or Bridging (100 k Ω)

Line input with BS preamplifier can be used for separate mixing of second microphone.

Line input with BM mixer can be used for separate mixing of three extra microphones plus line input.

Oscillator Frequency:  65 kHz

Output Level:  +15 dbm

Output Impedance:  600 Ω

Frequency Response:

At 15 ips :  30 c/s to 18,000 c/s ±1 dB

At 7-1/2 ips :  40 c/s to 15,000 c/s ±1 dB

Signal-to-Noise Ratio:  75 dB at 15 ips

Erasure:  - 80 dB

Temperature Range:  -4° F to +122°F

Power Consumption:

85 mA : in test mode

175 mA :  in Playback mode

205 mA :  in Recording mode

Batteries:  12 standard Flashlight "D" Cells

Dimensions :  12,5 x 8,7 x 4,3 inch

Weight :  13 lb 13 oz

Recorder Case:  Rugged lightweight metal

Carrying Case:  eveready feather case with or without padding

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