Wondering how can I eliminate click & pop noise?

Thread Starter

musicalavtech

Joined Mar 23, 2012
72
In my electric guitar, I want to install a slide switch in a good spot, on the back cavity cover. The switch would have the 9V battery neg lead (for the pre-amp) going through it. I want to switch it off when the guitar is in-between sets, but still plugged in. As wired now, the battery neg lead gets switched on when a cable is plugged in. I will rewire all that.

I assume that it will create a pop or click that would be going into the amp. So would a capacitor, or some simple component "ramp" the power off & on when the switch is opened or closed? Would that concept even get the desired results?
 

Dodgydave

Joined Jun 22, 2012
11,285
You're trying to create a Dethump circuit, best way is to short out the input to the amplifier with a fet or other device.
 

Marley

Joined Apr 4, 2016
502
Basically you need to short the output to the amplifier until the pre-amp has powered up and voltages stabilised. The simple way is probably to have a 3-position switch OFF - POWER ON - SIGNAL ON. Switch it slowly. The signal switch must short the audio when off. Don't have the switch in series with the audio signal.

A nicer way would be to have a JFET or relay switch that shorts out the audio until a short time after the pre-amp is powered up.
 

Thread Starter

musicalavtech

Joined Mar 23, 2012
72
Basically you need to short the output to the amplifier until the pre-amp has powered up and voltages stabilised. The simple way is probably to have a 3-position switch OFF - POWER ON - SIGNAL ON. Switch it slowly. The signal switch must short the audio when off. Don't have the switch in series with the audio signal.

A nicer way would be to have a JFET or relay switch that shorts out the audio until a short time after the pre-amp is powered up.

Sure enough, a 3 pos switch would do fine. Thanks.
 

Thread Starter

musicalavtech

Joined Mar 23, 2012
72
Basically you need to short the output to the amplifier until the pre-amp has powered up and voltages stabilised. The simple way is probably to have a 3-position switch OFF - POWER ON - SIGNAL ON. Switch it slowly. The signal switch must short the audio when off. Don't have the switch in series with the audio signal.

A nicer way would be to have a JFET or relay switch that shorts out the audio until a short time after the pre-amp is powered up.
Also I am wondering if the switch shorts the audio, (which does effectively mute the output) then that also means the output of the pre-amp will be shorted in the middle "POWER ON" position. I don't know if that should be a concern for a small pre-amp. Maybe a resistor would protect the pre-amp output, but not too much resistance to the signal short for mute.
 

Marley

Joined Apr 4, 2016
502
Should not matter if you short out the pre-amp output.

The reason for shorting out is that the pre-amplifier will have a series capacitor at the output. When the pre-amp is first switched on, this capacitor needs to charge up to its normal working voltage. The short provides a path for this charging current without introducing a voltage at the main amplifier input. This is why the short needs to remain for a short time after the pre-amp power is applied.

I would expect the pre-amp to not only have a series capacitor on the output but also have a resistor to ground at the output after the capacitor to maintain a 0V DC condition on the cable that goes to the main amplifier. This resistor will have a value that is high enough that it does not effect the audio signal but does carry the hopefully very low capacitor leakage current. Something in the region of 10K to 22k would be normal. The switch shorts out this resistor for a short time after power-up.

Making sure there is no DC voltage anywhere on the audio signal cables will reduce the chance of clicks or pops if the audio cable is disconnected and re-connected with the amplifier up.
 

Thread Starter

musicalavtech

Joined Mar 23, 2012
72
Should not matter if you short out the pre-amp output.

The reason for shorting out is that the pre-amplifier will have a series capacitor at the output. When the pre-amp is first switched on, this capacitor needs to charge up to its normal working voltage. The short provides a path for this charging current without introducing a voltage at the main amplifier input. This is why the short needs to remain for a short time after the pre-amp power is applied.

I would expect the pre-amp to not only have a series capacitor on the output but also have a resistor to ground at the output after the capacitor to maintain a 0V DC condition on the cable that goes to the main amplifier. This resistor will have a value that is high enough that it does not effect the audio signal but does carry the hopefully very low capacitor leakage current. Something in the region of 10K to 22k would be normal. The switch shorts out this resistor for a short time after power-up.

Making sure there is no DC voltage anywhere on the audio signal cables will reduce the chance of clicks or pops if the audio cable is disconnected and re-connected with the amplifier up.

Thanks so much. I'll give it a go...on 2 guitars.
 
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