Guitar amplifiers drive the speakers of the guitar by amplifying the sound that is supplied into them from the instrument. The guitar pick-up transforms the sound waves produced by the guitar strings into a small electrical signal, which is subsequently delivered into the guitar amplifier (or simply guitar amp). The guitarist may need to feed the guitar signal first into a pre-amplifier and then take the output from the pre-amplifier to feed the guitar amp, depending on whether or not the input of the guitar amp can work with the little signal coming from the guitar. For more details Line 6 Catalyst 100 Guitar Combo Amplifier
A guitar amplifier normally operates in four stages: input, signal modulation, signal amplification, and output.
The guitar pre-amp or the actual guitar itself might provide the input signal to the guitar amp’s input stage. The amplifier typically has input female jacks where the input signal cable is attached. The signal from the guitar should first travel through a guitar pre-amp if it is too weak to be fed directly into the guitar amp. It is crucial that the input signal impedances of the selected guitar amplifier and the available input signal impedance are properly matched. The final guitar sound that is heard on the loudspeakers is frequently degraded by signal impedance mismatch.
There are several guitar amplifiers available nowadays that include a pre-amplification stage. It is not necessary to send the guitar signal into a separate pre-amp when using such amps. The amp itself can receive the signal directly.
Stage of Signal Modulation
The typical electric guitarist does not quite prefer playing plain in and plain out. He desires a jazzed-up, twangy, funky, severely distorted, etc. guitar sound. Before they may be amplified, such sounds require modulation of the input signal. Let’s say the guitarist requests a sound that is heavily distorted and resembles heavy metal music. The input signal is routed into the signal modulation stage, where it goes through the necessary (yet controlled) distortion, to produce this kind of sound. The same holds true for various sound effects, such as wah-wah, reverb, etc. Equalizers and other tone control knobs are common in guitar amplifiers and fall under the category of signal modulation.
Stage of Signal Amplification
Any guitar amp’s “business” stage is the signal amplification stage. The guitar sound is actually magnified in this area. Good guitar amplifiers will faithfully multiply the signal coming from the Signal Modulation Stage, which means that the incoming signal will be a much stronger version of the stage’s output signal. Any amplifier, whether a voice or guitar amp, has the responsibility of faithfully amplification the input signal.
All guitar amps have a final stage like this. The output driver stage is a component of the output stage in some guitar amplifiers but not in others. The output signal from the signal amplification stage is sent straight into the loudspeaker in some low-cost guitar amplifiers. To ensure that the output signal is appropriately matched to the input requirements of the loudspeaker, good guitar amps incorporate a proper signal conditioning output stage.