This is a A/B Box switch pedal schematic with two inputs and one output and featured with dual operational amplifier modules. This circuit was designed by Rick Barker.
This A/B Box effect was originally designed for switching between different harmonica mics. This A/B Box featured low noise dual preamp for better performance.
IC 5532 types (example: NE5532, NE5532A, SA5532, and SA5532A which manufactured by Texas Instruments) are high-performance operational amplifiers combining excellent DC and AC characteristics. They feature very low noise, high output-drive capability, high unity-gain and maximum-output-swing bandwidths, low distortion, high slew rate, input-protection diodes, and output short-circuit protection. These operational amplifiers are compensated internally for unity-gain operation. These devices have specified maximum limits for equivalent input noise voltage.
Download the schematic of A/B Box Switch with Dual Op-Amps: