Abstract: An automatic calibration arrangement for a tape recorder is disclosed. The arrangement includes a microprocessor which responds to pre-stored calibration signals to write predetermined tones onto each track of the tape using the record circuits and record heads of the tape recorder, and then monitors the corresponding signals as replayed by the replay heads and replay circuits of the tape recorder so as to automatically adjust parameters of the record and replay circuits accordingly. The record and replay circuits are arranged to be settable by means of digital numbers produced by the microprocessor. Parameters which may be adjusted include record bias, record drive current (to produce 1% third harmonic distortion), and the mid band and band edge filter circuits, and phase adjustment of the replay circuits. Recorders not having replay circuits (but having replay heads) can still have their bias level and record current calibrated and can record replay calibration frequencies for external calibration purposes.