Clicks and pops when turn dial on switchbox - diyAudio
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Old 16th April 2002, 02:21 PM   #1
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Unhappy Clicks and pops when turn dial on switchbox

How can I eliminate the clicks and pops in a switchbox that I have made myself.

Each time I turn the dial into a particular position it has loud clicks and loud pops when turn out of that position. The switch was a DACT dial, good quality and the box has 5 pairs of in and 1 pair of out. Only using two inputs to select between the two currently.

Any suggestions?

Thanks in advance,
Chris
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Old 16th April 2002, 04:45 PM   #2
tiroth is offline tiroth  United States
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It sounds like you've got some DC bias on your inputs, which looks like an AC transient when switched in/out. I'm afraid I can't offer a circuit to address this, but maybe this offers you a starting point.

I built a simple switch and noticed similar behavior. When I run it through my ADC (which has DC offset removal) it is eliminated.
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Old 16th April 2002, 05:46 PM   #3
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Thanks,
I will check for DC at the inputs later today.
Chris
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Old 7th June 2002, 04:11 PM   #4
Alf is offline Alf
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Check the output impedence of the sources that you are switching. They are usally 47K. You may have to install a 47K resistor on each input line. The pop or click is caused by the output/input coupling caps. One input source will have a differance in potential/bias than the other.
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Old 7th June 2002, 06:10 PM   #5
MBK is offline MBK  Singapore
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Check the output impedence of the sources that you are switching. They are usally 47K. You may have to install a 47K resistor on each input line. The pop or click is caused by the output/input coupling caps. One input source will have a differance in potential/bias than the other.

hmmm. Do I misunderstand something... the output impedances of the sources is more likely to be 47 Ohms, not kOhms, and it's the input impedance of the following (buffer) stage after the selector that is likely to be 47k.

I have also sometimes problems with clicks on switches. My take on it is:

Could be capacitors / bias present; that alone would do nothing but it's the short time of non-contact while switching that confuses the following stage with an effective turn-on transient (first source 1, then no source, then source 2 connected to following stage). This is why some people use "meake before break" switches. I ain't got none of these myself. Solutions:

Have an input stage (buffer following the selector) that has a way of getting rid of the transient and/or does not lose its bias while switching. In practice, try this: measure the input impedance of the following stage. If it's infinite that means either
1a - there is a voltage follower (non-inverting) buffer with no R to ground as input behind selector. In that case put a 100k resistor from selector out to ground, or even as low as 10k. Or it could mean
1b - there is a coupling capacitor followed by a 10 k to 100 k resistor to ground after the selector. In that case try a 100 k to 1 M resistor to ground before that capacitor.

You can also try a resistor in series after the switch but I doubt it will help much, and it may mess up your gain, the distortion characteristics of the following stages, or even the filter function of the following stage, read, frequency response.

MBK
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Old 26th June 2002, 09:32 PM   #6
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try spraying the switch with some contact cleaner
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Old 26th June 2002, 10:52 PM   #7
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Is it a "make before break" or shorting type of switch?
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Old 29th June 2002, 05:53 AM   #8
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Position number 1 on the dial is for one preamp source L/R
Position number 2 - no connection
Position number 3 is for another preamp source L/R
...........................4 - no connection
...........................5 - no connection
...........................6 - output to power amp L/R

The clicks and pops only happen when connects number 3 to the newly purchased upsampler..The only thing I know about the switch is it is called DACT 4 pole switch allow for 5 pairs of input L/R and one pair of output L/R..

May be the upsampler has a different ground level, there is no DC detected at the connections...

Chris
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