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I bought a cheap computer Sub to repurpose it as a selfmade gaming vest. The circuit has 2 amplifiers on it, one for the normal unfiltered sound that goes to the 2 speakers, and then the output of this one is filtered and sent to a second amplifier for the subwoofer. The filtering is not great... I tried with a wave generator and got clear, loud sound up to 11.000 hz... I would like to add a low pass filter that has a cutoff frequency of 200Hz on the input of the second amplifier. I found a 1uF capacitor at home, and after googeling around i somehow came up that with that capacitor I would need a resistor of 820Ohm to have a cutoff frequency of roughly 195 Hz.

Is that correct? Wouldn't that resistor in series lower drastically the input volume to the amplifier?

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  • \$\begingroup\$ RC filter calculator \$\endgroup\$
    – ElectronSurf
    Dec 28, 2019 at 20:18
  • \$\begingroup\$ yep, already checked that.. so a 1uF capacitor and a 820 ohm resistor should give 195 hz cutoff frequency.. but what about the volume? \$\endgroup\$
    – sharkyenergy
    Dec 28, 2019 at 20:19
  • \$\begingroup\$ @sharkyenergy um, what about the volume? That designer tool gives you a bode plot. \$\endgroup\$
    – Marcus Müller
    Dec 28, 2019 at 20:28
  • \$\begingroup\$ @MarcusMüller, sorry, i am a mechanic and read about RC filters the first time 2 hours ago.. what is a bode plot? the signal going to the amplifier has an amplitude of about 20 mv... what worries me, is that adding the resistor will reduce the tension so much that i cannot hear anything... \$\endgroup\$
    – sharkyenergy
    Dec 28, 2019 at 21:08
  • \$\begingroup\$ i just tried with a 10uF and a 82 ohm resistor.. according to the simulator it should cut the frequencies above 200 hz.. what it did was lowering drastically the output on all frequencies... as soon as i removed the capacitor it worked normally again.. \$\endgroup\$
    – sharkyenergy
    Dec 28, 2019 at 21:21

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