alternating current amplification

kattoju said:

i was told the audio amplifier would filter out the low frequencies.....

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If the amplifier is AC (capacitor) coupled then it is correct.
However a DC coupled amplifier will, as its name implies, amplify all the way down to 0 hz (DC).

DC coupled amplifiers usually require +/- bipolar supplies, unless they are in the bridge mode.

kattoju said:

i was told the audio amplifier would filter out the low frequencies.....

Click to expand...

Most audio amplifier ICs use an input capacitor (and sometimes an output capacitor) to cut very low frequencies. If the capacitor value is increased then the amplifier will amplify very low frequencies. If the amplifier works with its input at 0VDC then the input capacitor can be removed and the amplifier can amplify extremely low frequencies including amplifying DC.