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Author Topic: 555 LFO causing interference / noise  (Read 6105 times)

wax+wire

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555 LFO causing interference / noise
« on: April 28, 2014, 12:56:23 PM »

I've got two projects with 555 based LFOs.  one is an APC/Atari Punk Console (so that is a lot of 555s in a box) - the other is based on Graham's Phat Philter Bank for the Casio SK5, a mono Voltage Controlled Filter.

I find that the LFO affects the output regardless of whether the control voltage line is connected or not!

Crazy.  In the Filter circuit it introduced a very obvious *click* in time with the rate of the LFO, and in the APC turning on the LFO (though still not connecting CV lines) causes pitch changes.

Do I need to shield my CV lines - could that be the problem?
What else could it be?

Thanks in advance
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wax+wire

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Re: 555 LFO causing interference / noise
« Reply #1 on: May 10, 2014, 02:48:39 PM »

if anyone else is having this problem:

https://sites.google.com/site/flofxdiy/deticking-lfo

I ended up sticking a 100nF cap over the positive/negative terminals which reduced the clicking significantly - but it is still slightly present.
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