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Fusion916 5th October 2012 04:55 PM

How to stop turn on pop noise in speaker
I build a 1w class A amp (my first) with a switch on the AC mains. Whenever I flip there switch, there is about a 1/2 a second 60hz pop in the speakers. What is the standard technique to suppress this?

RJM1 5th October 2012 05:46 PM

Probably an output protection relay which would delay the connection of the amp to the speakers for several seconds and disconnect the speakers on an amplifier fault.
You might start here.
Bu everybody has there favorites.

Fusion916 5th October 2012 06:49 PM

So basically you could do a RC delay + relay to connect to speaker?

Mooly 5th October 2012 06:57 PM


Originally Posted by Fusion916 (
So basically you could do a RC delay + relay to connect to speaker?

Yes, and it can be very simple. For example a small auxilliary supply is created (of your main transformer) using a single diode and cap. The cap is made small as this will determine how quickly the relay drops out. For the switch on delay the relay is fed from a FET with an R/C delay on the gate. It really is that simple. Just half a dozen common parts and a relay.

Mooly 5th October 2012 07:08 PM

1 Attachment(s)
Like this (I've taken this from an old thread of mine). The FET (IRF240 type) drives the relay. The cap and resistor on the gate set the on delay. The zener (say 12 volts) just clamps the gate voltage to ensure the FET Vgs rating is never exceeded. The reservoir cap is small (say 47uf). Not shown would be a 1N4148 diode reverse biased across the resistor to the gate. This ensure the timing cap is discharged immediately the power is removed.

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