Need some help converting an audio signal (speaker wir output) into a square wave.

Thread Starter

Michael Carlotta

Joined Sep 25, 2014
I am trying to get the compression side of an audio signal's sine wave into a 9V pulse and the decompression side of an audio signal's sine wave into a 9V pulse (not shown well in the sketch but I would use a cyclic relay).

I'm sure my sketch will get a chuckle out of you.

Thanks for any help.


Joined Mar 14, 2008
At what point on the audio signal do you want the pulses to occur? You diagram seems to indicate it's near the peaks.

Compression and decompression have nothing to do with the signal polarity. Normally the top of the waveform is called the positive side and the bottom of the waveform, the negative side.


Joined Sep 9, 2010
Window comparator. Turn on compression when voltage falls outside the window. (At least that's what I'm guessing you meant from your wording.)

ian field

Joined Oct 27, 2012

You might want to have a look at the TCA965.
I have used the chip in the past.

Last time I tried to buy a TCA965, I was told it was obsolete - and that was years ago.

The 555 has a window comparator input, but the thresholds are fixed at 1/3 & 2/3 of Vcc by an internal series chain of 3x 5k resistors - you can exert a certain amount of "pull" on the lowest resistor via the CV pin, manipulating Vcc to influence the upper threshold can get a bit fiddly.