Quadraphonic Sound System (4 channel Sound) circuit is the most sophisticated sound system and gives a true feeling of music. Monophonic sound system is the simplest of all the audio systems. Monophonic or the single channel music system is unable to give the feeling of space, depth and displacement. In the case of stereophonic reproduction two separate channels or amplifiers are used to drive two separate speakers. The, input to/the stereo system, unlike mono-systems, is fed through stereophonic cartridge or tape. In the case of stereophonic recording to separate units of microphones are used and are generally placed a few meters apart from each other. The signals received by these two microphones are recorded on the stereo record or the tape. On playing these stereo records or the tapes, two separate signals are recorded and are amplified through two separate amplifiers. Thus a stereo system is able-to give a three dimensional effect to the music reproduced from the record. Quadraphonic system is a further advancement of the stereo system. It is made up of four channels or separate amplifiers and safe is able to give a live performance effect. In case of a true Quadraphonic system circuit, quadraphonic records etc. are required, which means parting with a good lot of money. The electronic gadget, shown in figure 2, when connected to a stereo-system gives a quadraphonic sound effect. It does not require quadraphonic records or the pick up cartridges. It is not a true quadraphonic system but gives a pretty good effect. The unit is connected in between the pre-amplifier and the amplifier. The use of shielded wire for connections is recommended so as to cut down the hum and other objectionable distortions. The output signal from the unit is fed into two separate power amplifiers which operate the rear left and the rear right speaker columns. Thus a system of four separate channels; Right—front and rear; Left-front and rear: is formed and gives a quadraphonic sound effect. The ganged potentiometer marked as ‘Depth’ controls the spatial depth effect giving a true three dimensional feeling. The complete unit draws a very small amount of current and hence two nine volt batteries are used for the supply.
Parts Required :- l. Integrated circuits lC 741 2 Nos. 2. Potentiometer-ganged 100 K ~ 100K linear 3. Resistances (1/4 watt) 100K 6 Nos: IOK 2 Nos. 4. Presets :- 100 K 2 Nos.