The DP-3000 first detects the pulses recorded on the inside of the turntable rim with the magnetic head for speed detection, amplifies the pulse signal, passes it through a limiter circuit, and converts the speed change into a voltage change through a demodulator circuit. This voltage is then compared with a reference voltage set in advance to achieve the specified speed, and the difference in voltage is used to control the motor drive power supply voltage for servo operation.

This allows speed changeover to be easily performed by switching the reference voltage. The circuits and elements used are extremely stable, and provide highly reliable characteristics even when subjected to temperature change, secular change, and negative variation simultaneously.

For speed detection, the inside of the turntable rim is magnetically coated with a material with high magnetic resistance, and pulses of a certain wavelength are recorded with high precision and high density using a special method. These pulses are detected by magnetic heads mounted at intervals of approximately 1/10 mm.

With this method, the wavelength error of the recorded pulses is kept to less than 0.01%, and since the pulses are recorded at 1000 locations around the entire circumference of the turntable, the frequency of the detected pulses is approximately 550 Hz at 33 1/3 rpm speed.

This frequency is more than five times higher than that of other methods, allowing the time constant of the integrating circuit in the frequency-to-voltage conversion circuit to be significantly reduced.

A lightweight turntable with a weight of 1.1 kg and a mass of inertia of 160 kg-cm2 is used for the turntable, which speeds up the startup time and reduces the burden on the bearings, thus obtaining stable performance over a long period of time.