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

Acoustic Research Amplifier

 The AR amplifier will provide any speaker system with a signal source as accurate and powerful as is ever likely to be needed in the home. In addition, the AR amplifier offers the reliabilty and moderate price which are the objectives of every AR design.  The result is a unit which uses advanced silicon transistor technology and manufacturing and testing techniques developed by AR to achieve a level of performance comparable to or exceeding, that of the best professional recording or broadcast equipment of its type. This is shown in the technical data sheet published by AR, corroborated by independent tests such as that by CBS laboratories published in High Fidelity, and guaranteed by AR to remain correct .
 One of the most important characteristics of an amplifier is its power output. Consumers might therefore expect this measurement to be presented clearly and accurately in amplifier advertising. This has not been the case. In recent years, a variety of vague and irrelevant terms has been used by manufactures to describe power output; music power, transisor power, IHF power and others. The list includes terms invented by manufactures and applied to their products alone, as well as standards of measurement known only to advertising copy writers. In a recent issue of High Fidelity for example, 18 manufacturers advertised amplifiers, but in only two casas were power ratings referred to a known standard.
 Acoustic Research accepts the definition of a watt given in physics texts; work done at the rate of 0,7375 ft-lb/second. We know of no "music watt" or "IHF watt" which science tecognizes. AR amplifiers are rated exactly as we measure them, with both channels continuously delivering at least the rated power without exceeding our harmonic distortion limit of 0,5% or our IM distortion limit of 0,25%. The laws of physics and the nature of music require that power measurements, if they are to be meaningful, be made with a steady, uninterruptedtone, similar to the purest means. AR amplifiers must deliver their rated continous power at all frequencies to which the ear responds, non just at 1,000 Hz, where most amplifiers  can deliver much more power than at the extremes ofthe ramge of hearing. Distortion measurements are made through the AR amplifier's phono input because this is the way music goes through the amplifier - even though performance might be better with the preamplifier out of the circuit.
 For these reasons, the power output rating of the AR amplifier is true for any kind of musical tone, not only those easy for an amplifier to reproduce, whether the source is an FM broadcast a tape recording or a phonograpf record.
The workmanship and performance in normal use of the AR amplifier are guaranted for two years from the date of purchase.
 AR publishes a non-technical guide for consumers who want to know the basic facts about amplifiers, what they do and how they differ from each other. It is entitled, "You Don't Have To Be An Engineer", and is available free on request.
Power Output:
60 watts per channel RMS at 4 Ω
50 watts per channel RMS at 8 Ω
30 watts per channel RMS at 16 Ω
Rated with both channels running at full output at 0,5% THD or less, at any frequency between 20 and 20,000 Hz.
Harmonic Distortion:  less than 0,5% from 20 - 20,000 Hz
IM Distortion (60 & 7,000 Hz , 4:1):  less than 0,25% at any listening level to full power.
Frequency Response:  20 Hz to 20,000 Hz ±1 dB (indicated flat tone control settings, at full power or below)
Switched Input Circuits:  Magnetic Phono; Tuner; Tape Playback
Outputs:  Tape record; 4 - 16 Ω speakers
Input Sensitivity/ Impedance: 
Phono : 2 mV - 5 mV/50 k Ω
Tape PB, Tuner : 200 mV/150 k Ω
Signal-to-Noise Ratio: 
Phono :  57 dB
Tape Pb, Tuner :  75 dB
Output Impedance Tape Record:  5 k Ω
Output Impedance at Speaker Terminals:  0,2 to 0,5 Ω (depending on frequency)
Damping Factor: 
8 to 20 for 4 Ω speakers
16 to 40 for 8 Ω speakers
32 to 80 for 16 Ω speakers
Safety Features:  Line fuse; speaker fuses; Circuit breakers (self-resetting)
Circuit Characteristics: 
DC Driver clamping for clean overload recovery;
Idling power supply eliminates turn-on transient noises;
Bass and treble separately controlled for each channel;
Differential loudness compensation curves in bass control circuit;
Special null circuit permits exact balancing of stereo source material;
Stable under short-circuit of speaker terminals;
Built-in null circuit provides quick accurate means for channel balancing;
Color coded input and output conectors simplify installation,.
Power Input:  110 - 220 volts  AC, 50/60 Hz
Dimensions (H x W x D):  4-5/16" x 15-1/2" x 10" (without cover);  4-1/2" x 15-3/4" x 10" (with wood cover)

Weight:  19 lbs (8,64 kg)

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