What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

Harman/Kardon A402

 Amplifier-Preamplifier Harman/Kardon model A402 is a component of high fidelity audio system. The desig and manufacture of this unit we offer uncompromised reproduction of the music for your enjoy.
This component is equipped on  special display sensitivity.  Is comprised of a light-emitting diode display and four pushbutton switches that select mode of operation. The LED display is a faster, more responsive and, therefore, more accurate indication of dynamic range and power level.  The ranges for the display are established by pushbutton switches 1 and 2 under the display. Once the range is established the dB level of the signal below full scale is indicated by the calibration on the LED panel.
Completely sseparate power supply for each channel
Light emiting dioda (LED) output display
Double-lighted tone controls
Tape dubbing with isolated circuity
Two low-level and five high-level inputs
Wideband design with exceptional square wave response and phase lineality.
 The A402's unusual LEDoutput display, program control capability and complete tape handing features make it an extremely attractive value. But it is the transparent, detailed quality of its musical reproductionthat sets the A402 truly apart from conventional amplifiers.
Its exceptional performance results from designing for square wave response, phase linearity and extremely wide frequency bandwidth. The importance of this design concept is briefly explained in the section entitled:
Square Waves - Wideband Design and Amplifier Performance
Most amplifier are designed and tested with sine waves (single frequencies). These tests are useful for measuring certain kinds of distortion and we use them too. But sine waves are too simple to represent the difficult domands that musical signals make on amplifiers.
The square wave, composed of many frequencies (a fundamental and its odd-order harmonics), presents an amplifier with the same kind of complex load as musical sound. Ther is a direct and audible correlation between the quality of an amplifier's square wave response and the quality of its musical reproduction. Since a square wave represents many frequencies (10 times above the fundamental), an extremely wide frequency bandwidth is necessary in order to achieve really good square wave response. Precise square wave configuration also indicates excellent phase linearity. This ensures that at the depth and ambience of the original music will be preserved.

All Harman Kardon electronic components are designed for optimum square wave response, wide frequency bandwidth and phase linearity.
 The A402's LED power output display, much faster and more accurate than meters, gives a continuous, precise and easy-to-read monitor of the output. The display has two sensitivity ranges. The first position reads full scale at 40 watts (full output). The second control gives full scale readout at 6 watts.

Great flexibility in shaping program material is provided by hinged tone controls. The bass control provides 12 dB boost or cut at 200 Hz or 400 Hz. The treble control provides 12 dB boost or cut at either 5 kHz or 10 kHz. The high and low frequency filters have steep slopes which permit elimination of disturbing hiss or rumble without affecting program material.

The A402 provides complete monitoring facilities for two tape recorders. In addition, you can copy tapes from one machine to another while simultaneously listening to a third, separate program source by using the A402's special isolated tape dubbing circuitry.
 Except for absolute power, the A402 amplifier is the technical egual  of separate components that cost considerably more. And there are few components indeed that are its sonic equal.the A402 incorporates the latest refinement of the twin-power design Harman Kardon developed in 1959 for the Citation One amplifier. A design whose significant advantages are now influencing the thinking of other component manufactures. The A402 is driven by two complete, discrete separate power supplies, one for each channel. Even when music is extraordinarly dynamic, and the domands made on the amplifier are very great, the energy drawn by one channel will in no wayaffect the other. Twin power ensures excellent transient response and freedom from the overload distortion that can mask musical reproduction.
Power Output:  40 watts Minimum RMS per channel (both channels driven into 8 Ω, from 20-20,000 Hz,0,1% THD)
Power Bandwidth:  from 10 Hz to 60,000 Hz with less than 0,1% THD (both channels driven simultaneously into 8 Ω, at 20 watts per channel)
Frequency Response:
Less than 4 Hz to 160,000 Hz -3,0 dB
Less than 4 Hz to 100,000 Hz -1,0 dB
Square Wave Rise Time:
Less than 1,5 microseconds (power amplifier only
Less than 2,0 microseconds (system)
Square Wave Tilt:  Less than 5% at 20 Hz
Total Harmonic Distortion:  Less than 0,1% from 250 milliwatts to 40 watts RMS (both channels driven simultaneously into 8 Ω, 20-20,000 Hz)
Intermodulation Distortion: 
Less than 0,08% at 40 watts (SMPTE measurement)
Less than 0,04% at 1 watt (SMPTE measurement)
Damping Factor:  Greater than 50
Hum and Noise:
Power Amplifier Only :  greater than 100 dB
Tuner, Aux, Tape Monitor Input :  greater than 77 dB
Phono Input :  greater than 69 dB
Input Impedance:
Power Amplifier :  greater than 33 k Ω
Tuner, Aux, Tape Monitor :  greater than 33 k Ω
Phono :  47 k Ω
Input Sensitivity:
Power Amplifier Only :  1,2 volts RMS (rated power output)
Tuner, Aux, Tape Monitor :  125 millivolts (rated power output)
Phono :  2,2 millivolts (rated power output)
Overload:  90 millivolts input (Phono preamplifier)
Preamplifier Harmonic Distortion:
Tuner, Aux, Tape Monitor :  0,018%
Phono :  0,055%
RIAA Equalization:  ±1,0 dB
Preamp Output Impedance:  less than 600 Ω
Tone Control Effect:
Bass Hinge at 200 Hz :  ±3 dB at 200 Hz;  ±9 dB at 60 Hz
Bass Hinge at 400 Hz :  ±3 dB at 400 Hz;  ±9 dB at 120 Hz
Treble Hinge at 5 kHz :  ±3 dB at 5 kHz;  ±9 dB at 14 kHz
Treble Hinge at 10 kHz :  ±3 dB at 10 kHz;  ±9 dB at 28 kHz
Contour Effect:  +10 dB at 50 Hz;  +3,5 dB at 10 kh at -40 dB attenuation
Filter Effect: 
High Cut :  -3 dB at 3500 Hz  6 dB/octave
Low Cut :  -3 dB at 65 Hz  12 dB/octave
Dimensions (W x H x D):  394 x 134 x 375 mm (15 ½" x 5 ¼" x 14 ¾")

Weight:  11,0 kg (24 lb 2 oz)

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