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== Power Amp ==
=== Guitar Power Amps vs. Pure Power Amps ===
When it comes to power amps, there are two kinds. ''Guitar power amps'' are the ones built into complete guitar amps but can also exist as discrete units. They are designed to have some impact on tone, although not as much as a [[#Pre-Amp|preamp]]. They often use tubes, and may even be designed to be pushed into overdrive, or may at least offer differing tone at different volume levels. ''Pure power amps'' on the other hand, are designed to be as transparent as possible, only amplifying the input signal with minimal impact otherwise.
In earlier years, these different types of amps rarely crossed paths. Guitar power amps were for guitars, and pure power amps were for PA systems. With the introduction of modelers, which simulate guitar power amps, cabs/speakers, and microphones, pure power amps began to be used by the guitar community for amplification purposes. Rather than running them into guitar cabs, they'd run into full-range, full-response (FRFR) monitors. Some brands market power amps that bridge the gap, claiming they work for both purposes.
=== Headroom ===
The first thing to consider for power amps is their headroom, or their range of amplification before beginning to compress and distort. Typically, a good power amp offers lots of headroom, only beginning to show signs of distortion at the highest volume levels. Most modern high-gain amps try to contain all their distortion to the pre-amp, focusing the power amp on clean amplification. That said, some classic amps rely on power amp distortion to get their distinct tone.
=== Negative Feedback Design ===
Power amps may also offer various levels of negative feedback, which attempt to minimize any unwanted distortion (outside of overdrive distortion) created by the amplification process. Depending on the design of the amp, these may work wonders to offer a pristine signal, or introduce additional issues. An amp with good negative feedback will make the amp sound cleaner, more responsive, and have a richer tone. Again, however, the allure of some vintage amps is that the distortion their design allowed was found to be musically pleasing. The only way to know which amps have good or bad designs is to research and audition them individually, for your subjective taste.
=== Cab/Speaker Interaction ===
Power amps also have "interaction" with the speakers/cabinet they drive. So an amp may sound better paired with one cab than another, while another amp has the opposite response. In general, a good power amp will sound good paired with a wide variety of cabs - the change in tone will be mostly due to the different cabs used, not the power amp-cab interaction. However, it is something to keep in mind when choosing an amp.
=== Controls/Settings ===
Power amps typically have few if any dedicated controls. For many amps, presence resides in the power amp section, used to reduce the extreme high-end. Some amps may offer other controls such as a bass boost (deep) or modern voicing. Beyond that, the controls typically switch the way the tubes operate - pentode vs. triode, class A vs. class AB, full vs. half power. Some can switch rectifiers between solid-state and tube rectifiers (hence the title of the ''Mesa/Boogie Dual Rectifier''). Some also feature power sinks, so that you can overdrive the tubes without using extremely loud volumes.
== Cab/Speakers ==