Can somebody please describe/define all these different types of equipment or gear or whatever? Like pre-amp and the like.

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Well if you be more specific I can help but untill then here is what a pre-amp is. It is what your guitar sound goes into before it is amplified. All the eqing and effects take place here. All heads and combos have a preamp as well as a power amp. You can buy just pre-amps (i.e. PODs, any amp emulator, ect) and run that directly into a power amp which does nothing but amplifies your sound. It alters nothing from your tone. Usualy Power amps just have a volume knob.

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