Power hum

[Charles]

Can anyone point me to a circuit for eliminating a 60 cycle power hum.
I have a small transmitter connected to the audio output of my satellite
decoder and want to connect a receiver to the aux input on my Hi-Fi. It
works fine using a 3v battery supply but when connected to a commercial
battery eliminator, there is an unacceptable background hum. I think a need
a filter of sorts.

Thanks
Charles

 

[Tom Biasi]

"Charles" <ce.mason@telkomsa.net> wrote in message
news:cvnrqt$mdb$1@ctb-nnrp2.saix.net...

Can anyone point me to a circuit for eliminating a 60 cycle power hum.
I have a small transmitter connected to the audio output of my satellite
decoder and want to connect a receiver to the aux input on my Hi-Fi. It
works fine using a 3v battery supply but when connected to a commercial
battery eliminator, there is an unacceptable background hum. I think a
need
a filter of sorts.

Thanks
Charles

Correct, you need a filter.

A capacitor across the output may do the trick. You didn't say how much
current you were drawing but given the fact that you said a '3V battery'
you might try a 1000 UF rated 5V or a little more. Make sure the power you
are using is DC and watch the polarity on the cap.
Tom

 

[kell]

The filter capacitor the other guy mentioned is a good idea. That will
reduce ripple. And another possible source of hum is the rectifying
diodes in the battery eliminator. You can reduce that by connecting a
small capacitor (0.1 or 0.01 uF) across each diode in the bridge.