Can somebody explain these things : Power Amp, Pre Amp, , And noise gate, HOw they are used and stuff, what there used for, provide examples, thanks.
A pre-amp brings a low-level signal up to line level.
A power amp increases the amplitude of a signal to send it to the speakers (usually).
A noise gate sets a threshold below which a signal won't pass, and can sometimes be tuned to particular frequencies.
A typical signal chain might be to send the guitar through some floor pedals to a pre-amp, and then through some line level processors and then to the control board which will then direct the signal to the power amps.
A noise gate is really used most frequently as a recording tool, where some really neat tricks can be employed using side-chaining. But it does have some uses in live sound often in combination with delays and reverbs.
"The music business is a cruel and shallow money trench, a long plastic hallway where thieves and pimps run free, and good men die like dogs. There's also a negative side." -- HST
pre-amp amplifies both voltage and current. the former increases the voltage amplitude of the signal; the latter increases the ability of the signal to drive a line level impedance - anywhere from 600 ohm to 10k ohm load, depending upon the flavor of "line" level. (that is basically, as KP writes). the pre-amp often includes a tone stack (some or all of bass/midrange/treble controls) and/or EQ section.
however, a power amp increases the power of a signal mainly by current gain, which allows it to drive very low impedances (= Speakers).
the most familiar case: a guitar amp is usually the integrated combination of a pre-amp (input stages) and power amp (output stages).
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