With the amount of equipment in home entertainment centers today the need to be able to vary the gain of the audio or video signal is needed. I found this particular circuit helpful when used in conjunction with the Universal Descrambler and a Stabilizer circuit I built for making copies of video tapes. It not only allowed me the ability to fine tune the video strength it also helped me increase the recorded audio which typically becomes poor when making tape copies.circuit operation is straight forward for amplifier circuits. the second channel for the audio amplifier is made up of the same components except the other half of ic1 is used. pin 6 & 5 are inputs and 7 is the output.