This is 2 to 4 channel audio converter circuit using TL071, can be used on Car audio stereo systems that only have front speakers only a single page.
The circuit will increase the number of speakers up to the other two to be connected to the back speakers pair.
Amplifier signal circuit is a Non-inverting Amplifier using IC1 and IC2 is number TL071 op-amp IC input signal left (L) and right input signals (R) will stand at 3 (Non-inverting).
Of IC1 and IC2 Non-inverting Amplifier with 22 times the growth rate calculated from R4/R3 +1.
The VR1 and VR2 is the adjusted rate of growth of each channel output signal to leave the pin 6 through R5, C3 and R10, C6 (each channel).
To increase the stability of the signal better into output signals page left (LF) and Right (RF) signal and rear left (LB) and right back (RB).
Which VR3 / 1 and VR3 / 2 to adjust the volume of each channel. The rear left and rear right signals. Will be connected to a series of sector amplifiers.