BANG! From subwoofer when I turn it on (and off) at the wall.

[Robbo]

Hi,

A friend built us a sub (150W Amp, perfect cab dimensions etc).
It is a lovely unit however whenever I turn it on or off at the power point at the wall it goes bang!

Apart from never turning it off, how can I stop it banging?

Regards,

Greg Robertson
Victoria, Australia.

 

[Unregistered]

I need a little more clarification on "banging". Does the woofer emit a pop sound?

 

[Robbo]

The noise would be better described as a thump - pop noise.

 

[Unregistered]

I think you should get back to your friend to have the amp modified to address power surges when turning on the switch. I recall some capaitor or device had to be shunted across the switch to the ground to effectively do this. He should now know.

 

[Robbo]

Sounds like something we can look into. Thanks for your suggestion.

 

[Unregistered]

The noise would be better described as a thump - pop noise.

The output transistor in the amp is turning on when the power is applied. Your friend can do a number of things to prevent this, but it might be easier just to add a relay with a time delay between the amp and the speaker.

Make the time delay a few seconds - by the time relay closes, the amp's output should be stable.