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Clicky Switches
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ThirdPrize



Joined: Jul 01, 2008
Posts: 6
Location: UK

PostPosted: Mon Aug 18, 2008 5:58 am    Post subject: Clicky Switches
Subject description: Can i get rid of them?
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I am mucking around making my own little (sort of) synth based on a function generator (FG) http://www.cs-sales.net/fg500k.html kit. It makes a sine/saw noise perfectly but I am having trouble triggering it. At the moment i have the trigger between the FG and the output. It is a simple push switch that you can use to tap out simple rhythms. The trouble is that when you push the switch, it connects the circuit and enables the signal to be heard, but also makes a dreadful clicking noise. I agree it is probably not the best place to have the switch.

Power ->FG ->Switch -> Audio out

Now i have tried connecting the switch via a transistor (so its not directly on the signal line) and between the power and the FG but it still makes an audible click.

Anyone got any suggestions how I could smooth the the signal so it doesn't "click" so loudly or remove it all together? The signal gets sent to a guitar pickup via an old electromagnet. The idea being that it is a synth that you can play through guitar pedals and that will (to a certain extent) pick up feedback from the amp. It works great apart from these clicks.
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blue hell
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PostPosted: Mon Aug 18, 2008 12:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

A click is a sudden jump in the signal level that does not "fit into the signal" e.g when you have a square wave signal the signal has sudden jumps all the time but at regular intervals such that the clicks are heard as a tone - when however you would add a jump that does not fit in you'd still hear a click. A sine signal does not have such jumps of itself, but when you switch it on when the momentary level is not zero there will be a jump and a click.

Basically there are two ways to eliminate the click.

- 1 turn the signal on and off slowly, that is relatively slowly like say in about a couple of milliseconds. Then there will be no jump as the signal rises slowly.

- 2 turn the signal on and off synchronized to the wave, that is when the wave happens to be at the zero level - then there will be no jump as the signal is zero.


For the first method look for a simple Voltage Controlled Amplifier (VCA) and a simple Envelope Generator (EG). The EG is able to make a slowly rising and falling signal when you start resp. end the trigger signal. The VCA basically is a multiplier circuit, you feed it the signal on the audio input and the EG output on the control input, when the EG output is zero no signal (or very little) will be passed through (signal multiplied by zero), when the EG has a high signal all of the input will be left through (multiplied by 1), and in-between just a part will pass.

For the second method you could maybe use a solid state volume potmeter- aucxh devices usually provide the synchronization top the zero level, but it would likely need some digital circuitry to control it.

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also .. could someone please turn down the thermostat a bit.
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Antimon



Joined: Jan 18, 2005
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PostPosted: Mon Aug 18, 2008 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just testing to see if I've managed to learn anything about electronics:

Couldn't a "slower" switch be achieved by introducing a capacitor in the circuit around the switch? Maybe in parallell?

/Stefan

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ThirdPrize



Joined: Jul 01, 2008
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PostPosted: Tue Aug 19, 2008 2:15 am    Post subject: Reply with quote  Mark this post and the followings unread

I thought it might be somethig like that. I suppose that is why synths have Envelopes and all that stuff. What I have got is just the raw soundwave generator. That is probably something to bear in mind for version 2 of my synth.
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