| 摘要 |
PURPOSE:To vary steps of sound signals to be reproduced by using a common oscillation circuit containing a signal processing circuit, a spindle control circuit and a D/A converting circuit as a frequency variable oscillation circuit. CONSTITUTION:When the frequency of a frequency variable oscillation circuit 8 is increased, a reference clock 5B of a spindle control circuit 7 is also increased. As a result, a spindle motor 2 is accelerated to increase the number of revolutions of a disk 1. In this case, a digital signal 5D which is sent to a D/A converting circuit 6 from a signal processing circuit 5 is increased for its information quantity per unit time by a degree equivalent to the rise of the frequency of the clock 5B. At the same time, the frequency of a deglitcher signal 5C is also increased. Therefore an audio signal is compressed in the same ratio toward a time axis. When the frequency of the circuit 8 is reduced, a signal 6A is expanded in the same ratio toward the time axis. In other words, the time axis can be compressed and expanded in proportion to the changing degree of frequency. Thus the step of the audio signal can be varied. |
