Stereo preamplifier circuit is designed to amplify the CD players, tape recorders, MP3 player, etc. Stereo preamplifier circuit can provide a good enough gain to drive the power amplifier that is less sensitive. Many of these devices Hi-fi stereo home using a relatively small speakers, so that the frequency response of the bass cannot be reached with the good. For that the stereo preamplifier circuit is equipped with a bass booster.
You can use a variable resistor to adjust the bass level as desired. Bass frequency response in a stereo preamplifier circuit is 30Hz. The circuit shown in the picture is only for one channel (mono). Therefore, you must make two the same circuit to produce a stereo preamplifier. Specifically for Resistors R1, R2, R3 and C1, C2, C3 are common to both channels.
In stereo preamplifier circuit, some components, such as P1, P2 (or SW1), R4, R5, R6, R7, R8 and C4, C5, C6, C7 must be doubled. Pin Description IC in brackets show for channel left and right channels in a single IC. For stereo operation SW1 must be a DPST type. and last, please note that, using SW1, the boost is on when the switch is open, and off when the switch is closed.