In audio look at an amplifier. It will be always a voltage
amplifier.
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A headphone amplifier is a type of audio amplifier. Instead of
an amplifier that's designed to push through audio signals to
speakers, a headphone amplifier is designed to work with
headphones. These are common in devices such as MP3 players.
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The amp for audio freq. is a AF amplifier. The RF amp is for
radio freqs.
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There are many downsides of using an amplifier for one's car
audio system. Some downsides for using an amplifier for one's car
audio system includes bothering those around them due to the noise
and harming one's ears.