Small diaphragm dynamic mics are the most common choice for guitar amps, and the workhorse Shure SM57 is the one that most engineers reach for first. The SM57 performs just as well in the studio as it does on the stage, and with its extremely effective cardioid pickup pattern, small changes in angle or position can cause considerable changes to the sound. Even though it was introduced way back in 1965, it is to this day an industry standard. Some prefer its newer cousin, the Beta 57, which has an extended frequency response and a 4dB hotter output level.
Large diaphragm dynamic Microphones
Another popular dynamic mic for recording electric guitar amps is the Sennheiser MD 421, which unlike the SM57 has a large diaphragm and a five position bass control, enhancing its 'all-rounder' qualities. This is an extremely versatile mic which can be used to record a variety of amplifiers, instruments as well as group vocals.
Other common amplifier recording microphones from Sennheiser are the super-cardioid e606 and e906, which are designed to rest directly on the guitar amp's face, as did their legendary predecessor the MD409. Because of their design, they can be used without a stand simply by hanging the mic by its cable from the top of the speaker or combo, offering a subtly distinctive sound.
Even the most basic studio setup should have a condenser mic at hand, and every pro-studio will have a variety to choose from. Recording a guitar amp with a condenser mic will give you a very different result to a dynamic mic - a condenser mic alone often sounds a little transparent, but when used in conjunction with a dynamic (see the positioning section above) can give great results. Bear in mind that you will generally get a more acceptable sound from a condenser at reasonable distance from the amp, but here are no hard and fast rules to positioning, and again, taking the time to experiment will invariably get you the best results.
Most condenser mics have a pad switch due to their higher sensitivity which attenuates their output and prevents overloading at high SPLs - you will almost certainly need to employ this if recording close to the speaker.
Although relatively expensive and rather fragile, ribbon mics have recently undergone a resurgence in popularity, and one of their most common applications is in electric guitar recording, generally in place of a dynamic as a close mic - Royer's R121 is the favourite of many engineers. There are two key points to be aware of when using ribbon mics - phantom power can destroy them, and they all have a figure of 8 response pattern - this means that they will pick up sound from the rear as well as the front, so you may want to use some sort of acoustic baffle behind them to avoid too much room sound.
There are literally hundreds of different mics to choose from, and we have only mentioned a handful of the most popular models. If you have access to a range of mics then try some out that aren't listed here - you might just find the sound you're looking for.