METHOD FOR CONTROLLING MOTOR ROTATING SPEED, DEVICE THEREFOR AND RECORDING OR REPRODUCING DEVICE

PURPOSE:To accurately execute a servo control by obtaining a mean value at each interval of 1/n rotation of a rotary encoder and obtaining a required motor rotating speed control signal with this value as a reference value. CONSTITUTION:In this recording or reproducing device, traveling information of a magnetic tape 1 is obtained by the rotary encoder 12, and a servo control signal I is calculated by a motor revolving speed control part 21 based on this information. Then, this servo control signal I is converted into a voltage value corresponding to a frequency by an f-v converting part 22, and this value is given as a servo reference value J to a servo system between a motor servo part 23 and a reel motor 11, so as to control the revolving speed of the reel motor 11 to be a revolving speed for making the traveling speed of the magnetic tape 1 constant. In this case, the servo control that is more accurate than in the case of using traveling speed information by one rotation of the rotary encoder, can be carried out.