Circuit knowledge

The AN7147 Dual 5.3-watt Audio Power Amplifier from Panasonic is listed as a ‘replacement type’ so hopefully will be around for some time to come. Together with some extra components, it can represent a simple surround-sound system requiring no opamps or a negative voltage supply. As shown by the circuit diagram the basic stereo amplifier is changed into a surround-sound system by a trick called ‘adding feedback from the opposite channel’. When surround sound is required, the negative feedback signals supplied by C13-R3 and C12-R4 are fed to the inputs of the ‘other’ amplifier. The resulting phase difference causes the surround effect. If surround sound is not required, the effect can be disabled by pressing push-button S1.


This causes the bistable built around IC2.A and IC2.B to toggle and drive transistors T1 and T2 such that the above mentioned negative feedback signals are effectively shunted to ground. A high-efficiency LED and a 3.3-kΩ series resistor (R14) should be used to make sure the maximum output current of the CMOS 4001 device is not exceeded. The amplifier should not be loaded with impedances smaller than 3Ω. The AN7147 will typically supply up to 4.3 watts into 4 Ω. The SIL-12 case needs to be cooled wit a small heatsink of about 6 K/W or better. The quiescent current is modest at just 19 mA.

The circuit schematic drawings Surround Audio Decoder and its components and how to make it ,Audio surround decoder circuit. Surround sound quality is the process of adding the audio source by increasing the number of speakers. This is done by producing audio multitracking in a way that can be issued on a multichannel speaker.

Basically surround adopt an existing stereo system. The system uses a two-speaker stereo is right speaker and left speaker. With two speakers will be three-dimensional effect of the sound issued. With the surround, which generated three-dimensional effect was more extensive than in stereo. This is because the surround speakers that use more than two pieces. In addition to supporting the three-dimensional effects, stereo field theory is also noteworthy to organize the arrangement of sounds based on the type of sound produced.

Surround effects can only be listened to speakers who have more than two channels. Surround is a technique commonly used in todays films that utilize multichannel speakers. Surround allows voice can move from side to side, is a moving side to side is to move from one speaker to another speaker. To create three-dimensional sound effects you can use a series of audio surround decoder.