Simple RC lowpass audio filter

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nanZor

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May 28, 2009
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Just thought I'd make this stuff easier to find ...

If your receiver has a lot of hiss, or the filters are very wide, you may want to roll off the high end frequencies with a simple resistor / capacitor combination.

I've done this to various rigs to suit my taste. The basic stuff can be found here:

Speaker Noise Reduction Circuit Add on VE3VDC

and if you want to calculate it:

rc_simple_filter [Electron Coaxing Techniques & Notes]

TIP: If you have never done this, when you clip off the leads after soldering be SURE to have a firm grip on the lead with some pliers, otherwise the lead will get sucked into the speaker magnet, and forever buzz. Or, you attempt to retrieve it, but poke a hole in the speaker itself. Ask me how I know! :)

Also don't be in a rush and put the capacitors on the wrong side of the resistor...
 

cmdrwill

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Kind of like Hi Fi crossover circuits. Basically filters. A choke works very well in place of the resistor, much sharper roll off at higher frequencies. You could look up some Hi Fi speaker crossover plans.
 

nanZor

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For sure. Many outboard speakers incorporate inductors and other circuit components for more precise filtering.

This is intended mostly for beginner / quick fix type stuff on non-critical things like hissy top of rig cabinet speakers and such.
 
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