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Amplifier With Quadraphonic Pattern by LM1877
The circuit was designed using a four channel amplifier to produce quadraphonic sound: right front, left front, right rear, and left rear
- Quadraphonic – a sound production term wherein it uses four channels in which the speakers are positioned at the four corners of the listening equipment, reproducing signals that are independent of one another.
The goal of a quadraphonic sound system is to reproduce sounds in both the front and back of the listener, which simulates 360-degree sound. The overall gain ratio is controlled by the resistors R13 with R14 and R5 with R6. The gain is a measure of the ability of a circuit or an amplifier to increase the power or amplitude of a signal, usually defined as the mean ratio of the signal output of a system to the signal input of the same system. The values of the resistors are enough to fill a small room with sufficient audio output. There are instances where some of the outputs are growing without bounds known as instability, which can be prevented and controlled by the parallel combinations of resistors and capacitors. The instabilities are normally occurring on speakers with long wires.
The type of cables to be used should be screened to avoid grasping too much noise because of the long input cables and high impedance. Alternatively, a 10k ohm resistor can be positioned between points. Doing this will give higher noise immunity and a DC path to ground. The use of dual audio power amplifier LM1877 is due to the fact that it is designed to operate with a low number of external components and still provide flexibility for use in stereo phonographs, tape recorders and AM-FM stereo receivers. The LM1877 is internally compensated for all gains greater than 10 and may be derated at the assumed stress temperature of 150º C to an application to an application temperature of 55º C which may get hot under the presence of instabilities.
The use of quadraphonic is applied to different formats such as:
- hafler circuit, which imitates the effect of active matrix but without using costly electronics
- matrix H, which carries quadraphonic sound via FM radio in a way that would be compatible with existing mono and stereo receivers
- DY or Dynaquad, where the four speakers were arranged in a diamond format
- EV or stereo-4, which is used to produce credible 4-channel effects from 2-channel stereo recordings
- QS or quadraphonic stereo, which offers the advantages of diagonal separation and stereo compatibility
- SQ or stereo quadraphonic, wherein in the absence of a quad decoder SQ encoded records would play as normal stereo records by providing the full bandwidth from 20 Hz to 20 KHz to be produced giving much more open and detailed top end
- matrix, where the four channels are converted or encoded down to two channels
- quad-8 or quadraphonic 8-track, which is a discrete 4-channel tape cartridge system
- Q4, which was based on reel to reel type tape format that is fully discrete and has full bandwidth
- UD4 or UMX, which is a hybrid discrete/matrix system where only 35 to 40 items are encoded in this format and was marketed only in the UK, Europe and Japan
- CD-4 encoding or decoding matrix, which led to the production of conventional stereo LP records after failing due to the late FCC approval of FM quadraphonic broadcasting
- quadradisc, which was the only fully discrete quadraphonic phonograph record system to gain majority industry acceptance
- discrete, wherein the original four audio channels are passed through a four channel transmission medium and presented to a four channel reproduction system and fed to four speakers