BM543 distortion meter

The distortion is an alternation of a signal that has passed through a certain electric system (e. g. an audio amplifier). It is measured as a percentage of unwanted components in the distorted signal to the original signal. In high-fidelity audio electronics, the distortion shall be as low as possible. Modern audio amplifiers have the distortion factor as low as 0,001 %. This instrument can measure the distortion only in the tenths of percent, which is insufficient for modern uses.