A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for amplification or further processing. A preamp is often placed close to the sensor to reduce the effects of noise (noise) and interference (radio frequency).HiFi Preamp used to increase the signal strength to drive a cable to the main instrument without significantly lowering the signal-to-noise (SNR). Noise performance of the preamplifier is very important; based formula Friss, when the gain of the preamplifier high SNR of the final signal is determined by the SNR of the input signal and the noise figure of the preamplifier. HiFi Audio PreAmp Circuit TL072 Schematic Non-Inverting preamp Basic Component Selection and Functions U1 is the TL072 IC OpAmp is used as a reinforcing component. IC specification is pretty good with low prices and adequate sound quality. FET input type that has an extremely high input impedance. R1 is a bias resistor to the U1. we can actually increase the value of R1 (in order to have a higher impedance) due to very high input impedance U1, but this will also affect noise preamp (so higher). R2 serves as a counterweight between the impedance-ins and + in. Impedance balancing will help lower distortion. Its value is the result of parallel R3 || R4. R3 and R4 is a negative feedback resistor, is used to measure the output signal and determine the strengthening of the value: R4 / R3 + 1, ie 2x or 6dB. If the value of R4 and R3 are too high then the nosie will increase, if the value of R4 and R3 is lower then the noise will be lower, but the load on the U1 will be higher and may cause increased distortion. R5 serves to empty the C2 flows so as to reduce noise "bump" when the connector is connected. R6 serves to prevent oscillation due to the use of the cable sheath is long (more than 2meter).