"pop" sound when turning off tube amp...

[fabchef]

hi gang. i have seen a post here about a "pop" sound ( coming out of speakers, no matter in input) when shutting off amp. I have this situation (fairly often" when shutting off my old HK integrated amp (300A). As was mentioned, it would be good to install an arc supressor (disc cap) on the power switch? can anyone help as to what rating or what type of cap to install?what should i be looking for? i guess you install the ends on the ends of the power button wire? any info would be great! thanks
fab

 

[Mr Boochie]

The speakers still "pop," if you turn the volume down to zero, before turning the amp off?

 

[fabchef]

Boochie...yes. J always lower the bolume to 0, before shutting it off and it still pops.

 

[s-petersen]

Likely an xy safety cap across the power switch would fix that

 

[fabchef]

S-peterson....what do these caps look like? What ratings should i look for? Do you have a link as to what they are?
Thanks
Fab

 

[s-petersen]

Usually they are rated + 250vac and called a safety capacitor. They are usually either rectangular or dipped like an orange drop.
This thread may help

https://audiokarma.org/forums/index.php?threads/x1-y2-safety-capacitor-recommendations.971981/

 

[fabchef]

S-peterson...so is it one one type, or one rating for any type of unit? Does it go by thr rating of the amp? Thanks

 

[s-petersen]

It is one type, it is a filter to suppress the arc / spike when the switch is opened

 

[Mr Boochie]

Quencharc.

Maybe, try a 0.1mfd/150-ohm 250VDC/125VAC or 0.5mfd/150-ohm 250VDC/125VAC unit?

Quencharc units.

 

[StepheK]

Something like this should work.

https://www.mouser.com/ProductDetail/72-VY1472M51Y5VQ63V0

 

[fabchef]

Thanks gang. In terms of installation, can i just install it at the end of the switch/button wires? Is there a polarity to it?

 

[s-petersen]

yes, no polarity

 

[Mr Boochie]

For Quencharc device, I put the cap symbol on the hot side of the switch. The resistor symbol on the switched side.
This is just my convention. Prolly doesn't matter.

 

[Tom Bavis]

Since the power switch is probably under a shield, you can put it across the transformer primary, The switched outlet is an easy location to use. Just a cap is usually enough - I've never needed a resistor (though 68-100 Ohms would be ideal). .01 may be enough, biggest you'll find in Y-type ceramic.

 

[Essay]

It is important that you use a capacitor that always fails open. I think these safety caps have that.