NE566 - Music Synth / HAM Function Generator LM566 566

Amazingly, the NE566 can be made to sweep a continuous 1000:1 frequency span with just one fixed timing capacitor. Imagine, continuous linear tuning 20 Hz - 20 KHz or 1 KHz - 1 MHz without switching. A simple op-amp circuit provides the precise voltage control necessary. You set the range with the selection of the timing capacitor.

In our lab tests, we used a 0.047µF timing capacitor to achieve a sweep from 23 Hz to 49.5 KHz. That's an amazing 2150:1 ratio! Waveform symmetry does degrade at the very low end however, so if that's critical, a 500:1 or a 100:1 ratio may be more acceptable.

Even at a 500:1 ratio, only two timing capacitors (one hardwired, one switched) will allow you to sweep across the range of the NE566 from 4 Hz - 2000 Hz and then 2 KHz to the 1000 KHz, F_MAX.

Frequency is inversely proportional to the capacitance. Use the 0.047µF as a reference. Double it to halve the frequency, halve it to double the frequency, etc. Voltage, tolerances and circuit layout affect results so it's difficult to calculate exact capacitor values for your desired range. We can get you close with the schematic. From there you'll have to experiment. But it's not hard at all. E-Mail us for the schematic.

The NE566 is also used in many vintage arcade pinball machines such as Asteroids to generate those familiar warbling "UFO" sounds. Another use is as a transmitter in a high quality, low distortion Remote FM Speaker System described in AN-146 (132K PDF).

Finally, for serious DIY MUSICIANS, an excellent book, "Making Music with the 566" by synth guru Thomas Henry shows how to do tricks with the NE566 that even the manufacturer didn't know it could do. We don't stock the book, but it is, without a doubt, the best source available on this part. We highly recommend it. It was out of print for a few years but it's available again. Google the title to find it.

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