[sdiy] DCO with OTA fiddlings (semi-beginner question)

Tom Wiltshire tom at electricdruid.net
Wed Mar 23 20:45:34 CET 2016


On 23 Mar 2016, at 19:00, "Needham, Alan" <Alan.Needham at centrica.com> wrote:

> Will a conventional saw to tri waveshaper not also generate an audible click, and often of quite a size?

Imagine what happens when you rectify a sawtooth. The bottom folds up to the top, and if everything was perfect, the two saw peaks meet and make a perfect triangle (although unipolar).

In practice, there's a non-zero sawtooth reset time, so the two peaks *don't* meet and there's a little "chasm" between them, all the way back down to zero volts. That's the click. The faster you can get the reset time, the more the click is composed of high frequencies, and the easier it is to remove with a little bit of filtering. Many triangle wave shapers include a small capacitor somewhere for this job.

Note that you don't get the spike at both top and bottom of the triangle, only on one side.

Tom





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