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 ElecronicsEdC 16th April 2011 07:34 AM

If anybody is hearing RF OR a radio station
this is for you..

it's based on the reactance of a capacitor

1\ 2 PI F C

this gives you the ohms seen By ac in the capacitor at the given frequency

anyhow
if you simply place .1uF ceramic capacitors on your inputs to ground.

the noise will stop !

 ElecronicsEdC 16th April 2011 09:27 AM

http://www.sengpielaudio.com/calculator-RC.htm
here's an online calculator

ok using the calculator you can see that at 20khz the cap looks like 79.57 Ohmns to ground
this would roll of some of you HI's in a full range system

to the radio signal it's a straight short to ground

.01 should be tried first : especially in full range application because
.01 at 20 khz = 795.7 Ohms

 cviller 21st April 2011 07:10 PM

Thanks for the info. I actually had a mexican radio station on my chip amp while I was living in San Francisco.

 AndrewT 21st April 2011 07:37 PM

Quote:
 Originally Posted by ElecronicsEdC (http://www.diyaudio.com/forums/chip-amps/187148-radio-interference.html#post2540215) If anybody is hearing RF OR a radio station this is for you.. anyhow if you simply place .1uF ceramic capacitors on your inputs to ground. the noise will stop !
100nF seems far too high for RF attenuation.
Most will use an RC time constant of 100ns to 1500ns.
1k0 source resistor normally requires a 100pF to 1n5F to achieve those RC values.

0u1F cuts far too much treble.

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