Popping sound when switch off.

I recently build a gainclone LM3875 amp. It sounded very nice but:

A. a loud popping sound occurs during switch off. Afraid it might damage my speaker.

B. 1 channel appear to have intermittent crackling sound.

Please advice on how to solve this problem.

There are many versions and variations of the GC amp.
Could you please furbish the built and the schematics that it was based on?

1. Does the amp have a mute button ?
If yes, engage the mute button before switching off.

2. If no mute button, turn the volume all the way down to zero before switching off.

As for the intermittent crackling sound, it could be due to the source as well. If it is intermittent it is very hard to diagnose so you might have to live with it. Your best bet is to observe and note down the prevailing conditions when the sound comes - e.g. what CD or LP you are playing, what is the wall voltage (if you have a voltage meter), anything happening nearby maybe a light was switched on or off, washing machine, water heater, etc.

I believe the popping sound while switching off is normal for most equipment that prioritizes on audio signal purity. It basically mean lesser relay switches and more direct connection inside the circuit. Happen everytime to my Epxosure 2010s2 when i go on and off with the power switch.

While the cracking is truly something abnormal.

The higher end amps tend to have some sort of isolation to prevent the popping sound when powering off. But it usually works only if the power switch is used, not if there is a power cut. But it is true that often popping sound is a sign of a minimalist design - i.e. attemptes to get best sound at a sane price. Crackling can also be due to minimalist design, when the circuit is so sensitive that it detects interference. E.g. my system gives a few pops when I switch my flourescent light on in the room.

ya!my friend have one ps audio amp have some problem also.and the dealer said is capacitor problem.

Thank u guys for the advice. I may have found the solution. The popping sound is cause by the arching of the switch contact during switch off. It is due the reactive load such as transformer or motor. By connecting a snubber capacitor across the switch terminal will solve this problem. Refer to RS Component page 71 under chapter capacitor. Recomended rating is 100nf, 100ohm, 250Vac, RC network type of snubber capacitor. Cause RM8.90/pc . Hope this information is useful for those who having this problem.