ac switch noise

[71challenger]

Hi, I have an ac switch conneceted to my power amp cooling fans(fans are not part of the amp). If I run the amp hard I turn on the switch to start the fans. I get a popping sound in my speakers as the switch is turned on or off, regardless of the amps volume setting. What can I put across the switch to attenuate the arcing noise? a mov or a cap? And what values? I think the fans draw about 60-70 watts. Thanks in advance.

 

[ljcox]

Are the fans powered by the mains or from DC?

 

[71challenger]

Are the fans powered by the mains or from DC?

the fans are ac 120v

 

[ljcox]

the fans are ac 120v

You could try a mains rated capacitor in series with a resistor across the contacts. I don't know what values you would need, it depends upon the inductance and resistance of the motor. As a guess I would say 100 nF and 220 Ohm.

However, you may also need a filter in the DC supply to the amp.

Does anyone else have any suggestions?

 

[Sceadwian]

The filter cap and resistor should go a long way to prevent clicks. If I'm not mistaken many AC motors are current limited at their running impedances only, during startup they draw incredible amounts of power and that's causing your amp to undervolt for a split second. lj's right though this may be preventable by increasing the size of the amp's DC supply as well.