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Neil, Engineer
Category: Consumer Electronics
Satisfied Customers: 3764
Experience:  NZ Certificate in Engineering Electronics & Computing 25 years exp
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I have a TOA 912 PA amp. How can 8 get rid of AM station RFI

Customer Question

I have a TOA 912 PA amp. How can 8 get rid of AM station RFI coming in at the speaker lines? 70 volt system.
Submitted: 1 year ago.
Category: Consumer Electronics
Expert:  Neil replied 1 year ago.


How far away from the radio mast are you?

I am assuming you must be close for the interference to be picked up by the speaker lines...

Customer: replied 1 year ago.
About one mile, also have a lot of cat 6 running parllel to and close to the speaker lines.
Expert:  Neil replied 1 year ago.

Normally the keypad comes apart (either by plastic clips you have to release with a flat head screwdriver, or via a screw... The bit with the electronics on and is attached to wires comes off leaving just the back plate on the wall...

Expert:  Neil replied 1 year ago.

Sorry wrong question... standby...

Expert:  Neil replied 1 year ago.

Ok one mile is quite close...

Have you tried removing the input and see if the interference disappears...

Usually the interference gets into the front end of the amp, one way to prove this is to determine if the interference volume changes when you turn up or down if it does then its getting into an input, if it doesn't then its direct into the speaker lines

Customer: replied 1 year ago.
All cables are removed except speaker lines and power cord, no change in volume with master of channel cobtdol.
Expert:  Neil replied 1 year ago.

Then unfortunately not a lot can be done other than to use RF supressors on both the power feed to the amp as well as on the speaker lines at the amp end...