I'm looking for a quick-and-dirty way of converting something close to a sine wave to a narrow pulse wave. Please see the image: a low bass note played through a broken transformer. I'm trying to re-create the effect, preferably using discrete components.

narrow pulse waveform

  • 1
    \$\begingroup\$ try 'Low pass filter + zero crossing comparator'. \$\endgroup\$
    – nidhin
    Nov 19, 2014 at 8:12
  • \$\begingroup\$ Yeah I was thinking of some sort of a zero crossing detector. But I'm not good at designing circuits and I haven't really found a simple low voltage one (preferably with transistor(s)). \$\endgroup\$
    – Jari
    Nov 19, 2014 at 8:31
  • \$\begingroup\$ It is very important to perform lowpass filtering (integration) prior to zero-crossing detection. \$\endgroup\$
    – LvW
    Nov 19, 2014 at 10:27
  • \$\begingroup\$ OK thank you! I found this circuit, a good one to start with? sound.westhost.com/appnotes/an005-f1.gif \$\endgroup\$
    – Jari
    Nov 19, 2014 at 12:06
  • \$\begingroup\$ You show an output waveform and clearly there are pulses but what is the stuff in-between - is it noise that you don't want or part of the input signal? Are the pulses coincident with a certain part of the input waveform i.e. zero cross of input or possibly the peak voltage? Are there in fact many pulses per cycle? I cannot tell because I can't see the input waveform. \$\endgroup\$
    – Andy aka
    Nov 19, 2014 at 13:14

1 Answer 1


There is a way to convert a cosine and sine waves into a pulse. I do this in RF.

First of all you have to have both real and imaginary waves. We start with just a real wave and then perform a complex multiply. After some digital filtering you get both real and imaginary waves. For my project there are about 2 or 3 cycles at some frequency.

From trigonometry, cosine^2 + sine^2 = 1;

Your perform this equation on each sample.

This will give you a pulse.


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