Clicking from 4066

Cynosure

I don't have a schematic at the moment because my schematic app is on my laptop, which i left at the office. I will try to describe it instead...

I split a sound source.

A 40106 Schmidt trigger oscillator generates a pulse.

I send the pulse to a 4066.

The 4066 switches on and off one of the splits from the sound source.

I send switched sound from the 4066 to one end of a pot, and the other split to the other end of a pot, and take my sound out from the center pin.

This works as a sort of ON/OFF LFO, with the pot controlling the amount that the sound goes OFF and ON.

The only problem is, at higher frequencies there s an audible click that comes though - even when the pot is turned all the way to the original source split side.

Is there any way to lower or remove the clicking? I don't know if it is the 40106 pulses, or the 4066 turning on and off.

I tried using a cap to ground where the pulse connects to the 4066. That helps, but does not totally resolve the problem (it seems to lengthen the pulse width a bit too).

bubzy · Posted: Tue Sep 27, 2011 4:55 am Post subject:

hey cyno,
this is a totally unfounded, wild guess. i havent tested it and tbh i have never used a cmos switch(to date).
you could try "debouncing" the switch as you would do with a normal switch, so put a capacitor across the poles.
but as i said this is a wild guess. could be worth a shot though

stolenfat · Posted: Wed Sep 28, 2011 2:54 pm Post subject:

sounds like a pretty lo-fi attempt to rig something up... which is very admirable (and of course, preferable with lunetta madness) but easily can cause unexpected strange electro anomalies.

If the click is a full on thud, you could try improving the power supply circuit.
Maybe a cap or resistor to ground on both audio lines before they slam into the pot may help (via the ol' pseudo passive filter method)

Judging by the nature of the 4066 switcher, which i believe is a pseudo solid state relay, the clicking described is probably not coming from the chip itself but likely from the 40106 control pulse source: Odds are there's something passing through the common ground lines that needs to be investigated.

And just to understand I get what your talking about... i doodled up a quick schematic as i interpreted your description, is this correct?
Sounds like a great little circuit idea in theory.

schemmy.PNG

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Cynosure · Posted: Wed Sep 28, 2011 7:39 pm Post subject:

Yes - good job with the schematic. I will try to find some time to test all these things this weekend.

Thanks for the suggestions stolenfat and bubzy!

Psyingo · Joined: Jun 11, 2009 Posts: 248 Location: Canada

as far as i am aware electronic switches like the 4066 have capacitance coupling between gates, ins, outs, etc. due to the thin barriers in the chip...

this is just inherent, if i am correct.
there are ways of getting around it, like adding the same leakage signal to the output, but inverted, to cancel it out. but that can be quite tricky

someone more knowledgeable should chime in though...

Mongo1 · Joined: Aug 11, 2011 Posts: 411 Location: Raleigh NC

A few thoughts -

How big is that pot? If it's a low value you might be sending the stuttered output back into the input somehow. Try a bigger pot..

There may be a DC difference between the source and the 4066 output, so when the switch happens it results in a pop. It's possible that you might want to put a series cap on the input, or even on the output line.

One approach you could try - disconnect the 4066 output from the pot. If you can still hear the pop, it seems likely you've got a decoupling issue on the power supply.

What are driving this source from? If it's a high impedence, it may not be able to drive the source sufficiently.

just spitballing - hope it helps

Gary

Kabzoer · Joined: Feb 07, 2011 Posts: 82 Location: Belgium

Oh, and maybe you can try both 4066 and 4016, Their internals are a bit different, so you might have better results with one of them!

Cynosure · Posted: Fri Sep 30, 2011 6:49 pm Post subject:

Here is an update:

I removed the pulse to trigger the 4066, and there is a quiet high pitched click.

When I connect the pulse to the 4066 I get a louder thud.

I'm assuming that is a power supply issue? How do I go about decoupling to resolve the issue?

Cynosure · Posted: Sat Oct 01, 2011 4:45 pm Post subject:

Also, I did decouple the main power source at the 7809 I am using, and I have a cap from the power pin to ground on the 40106 to prevent starving since it is a large circuit (this is just the latest addition to the circuit).

I was playing around with it lastnight and couldn't resolve the issue, but I did come up with a better option for the lfo - instead of just turning off and on it instead turns on a passive low pass filter (cap to ground). sounds cool.

Cynosure · Posted: Tue Oct 11, 2011 5:47 am Post subject:

I have been playing with this circuit again, but this time as a stereo widener. It is a completely new circuit on breadboard, and I get the same clicking on the outputs.

The widener works nice, but the clicking is annoying at low speeds and starts to create an audio sound at high speeds.

Any other insights into this? My guess is that it is the 4066 - either the switching causes the click or the 4066 allows a bit of the pulse signal to leak through.

Anything else i can use to replace the 4066 that you know won't click?

astroman · Joined: Sep 13, 2012 Posts: 44 Location: UK

I've had this issue before, not with Lunetta's but with ring mods. Never able to eliminate the click

Cynosure · Posted: Wed Oct 31, 2012 5:28 am Post subject:

Wow - this is an old thread...

I have had better success with use transistors to do switching. They seem to switch a little quieter than the 4066, but you have to make sure that you lower both the sound input level and the switching signal and then boost it afterwards (which adds noise).