For questions about amplifiers in a musical setting. If the question is about a specific topic of amplifiers like maintenance or repairs those tags should also be included.
The amplifier is an important part of the performance set-up for electric guitars and keyboards, and makes a big difference to the tone. Other instruments and vocalists can also use amplifiers to be louder, either to balance with other amplified sounds, or just to fill a larger performance space.
If you're interested in using amplifiers in ways that don't specifically relate to musical practice and performance, for example as part of a home sound system, or in a suite for editing recordings, you will probably get better answers if you instead ask on the Sound Design Stack Exchange.