Abstract: A transistor amplifier utilizing AC, for an orchestral instrument, having a non-inverting input, with a predetermined range of linear amplification, a feedback means including a first path independent of transistors for controlling the input within said predetermined range, a supplementary path parallel with said first path and including a zener diode having a breakthrough point at the upper limit of said range, and a plurality of auxiliary paths having breakthrough points higher than that of the supplemental path, and each including a resistor and a zener diode, and arranged with the resistors in parallel and the zener diodes in series, forming a cascade arrangement, and the auxiliary path together being in parallel with the first path.