20 Hz to 25 kHz TDA1514 amplifier integrated subwoofer amp used in the cabin floor bass filter TLC272 opamp used symmetrical +-27v supply voltage to feed the olrak opamp zener diode made ​​R12 regulated. TDA1514A TLC272 20Hz 25kHz RMS... Electronics Projects, 20Hz 25kHz Subwoofer Amplifier Circuit TDA1514A "audio amplifier circuits, ic amplifier, " Date 2019/08/01