I'm trying to play a wav file from arduino through a mono amp with the low pass filter at the input but my output on the speaker is very noisy. Do I need a high pass filter at the output for DC offset? How do i calculate the values?
Are you using an audio shield?
A regular Arduino doesn't have a digital-to-analog converter. If you are using analogWrite() and 8-bit PWM, you're going to have lousy sound quality.
You may need to use capacitor coupling between the PWM output and the amplifier to eliminate the DC offset. 1-10 uF will work.