A preamplifier (preamp) is an electronic amplifier that prepares a small electrical signal for further amplification or processing.
A preamplifier is often placed close to the sensor to reduce the effects of noise and interference. It is used to boost the signal
strength to drive the cable to the main instrument without significantly degrading the signal-to-noise ratio (SNR).
The noise performance of a preamplifier is critical. According to Friis's formula, when
the gain of the preamplifier is high, the SNR of the final signal is determined by the SNR of the input signal and the noise
figure of the preamplifier.
In a home audio system, the term 'preamplifier' may sometimes be used to describe equipment which merely switches between different
line level sources and applies a volume control, so that no actual amplification may be involved. In an audio system, the second
amplifier is typically a power amplifier (power amp). The preamplifier provides voltage gain (e.g., from 10 mV to 1 V) but no significant
The power amplifier provides the higher current necessary to drive loudspeakers.