Buffer amplifier

In audio there is frequently a requirement to provide a low impedance, high current line level output for driving cables in excess of 1m in length. This situation typically occurs with passive preamplifiers, where the sound often appears "gutless" unless the interconnects are extremely short. A passive preamplifier may be used to drive a power amplifier directly provided that the interconnect is relatively short and low-capacitance. In general, however, the preamp sounds best with high-quality buffer amplifiers placed between the attenuator sliders and the preamp outputs. The stereo buffer amplifier enables the preamplifier to drive long cables with no loss of quality. The stereo buffer amplifier is based on OPA134 or OPA627 op-amps in a unity gain configuration, although provision is made on the pcb for setting the gain to any desired value, powered from a "wall-wart" stabilized psu for lowest hum and noise. There is 150mA of surplus ±12V power for any other circuitry you may care to use. The buffer amplifier is DC coupled, but there is provision on the pcb for 4.7µF polypropylene film capacitors at the input and/or output.