crystal controlled stroboscope

4-26 — elektor april 1981 crystal-controlled strobosco Why it is so essential for a turnable to have the correct speed? Well, for the simple reason that the slightest devi- ation will affect all the frequencies and tempi on the record. In other words, the pitch may change. This can, of course, lead to various interesting "special" effects, but it is hardly "high- f idel ity"! The above can be avoided by using a crystal-controlled stroboscope. This can be used to calibrate the turntable speed if some means of motor speed adjust- ment is provided. This type of record player is often equipped with a separate stroboscope disc (see figure 1) that can be placed on the turntable. When this is very constant over a short period of time (only long-term accuracy is re- quired to keep clocks and the like, running on time). In the second place, the image which appears on the strobo- scope disc is often rather blurred. This is because the stroboscope lamp is supplied with a sine wave derived ...