The authors describe a low‐cost ultrasonic amplifier suitable for animal studies. The amplifier delivers 100 V to a solid‐dielectric loudspeaker at 100 kHz, with a 2 V peak‐to‐peak drive. It uses a quasicomplementary, symmetry transistor output stage with short circuit protection. The authors also discuss the problem of identifying crossover distortion while driving a capacitive load.