This be the circuit filters 10KHz low size frequencies s use IC op-amp the highly popular number uA741. By this circuit convenients for to apply to input and output of the circuit changes analog signal be digital or the circuit changes digital signal be digital. In sound system of digital for synthetic the voice or music give for make wave form output the smooth. And press the noise that happen at output. When small-sized signal was managed with decrypt linear the size is 8 bit.