Abstract: A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting.