While many guitarists play both acoustic and electric instruments, when it comes to amplifying an acoustic guitar, there are many different things to consider. Electric guitar amplifiers are very different from acoustic guitar amplifiers. Many acoustic players prefer to use a direct box to plug the guitar into the PA to get a clean sound. However, if you are looking at an amp for your acoustic guitar, choosing an acoustic amp is better than using an electric amp.
Electric guitar amps are designed to be part of a guitarist's sound. They distort the signal, and electric players enjoy trying out the different sounds that they can achieve with different amplifier models from different companies. Electric amps can be made with either tubes or transistors. Most guitarists prefer tubes for the creamy distortion they produce. By contrast, acoustic amplifiers are designed to reproduce the original signal as truly as possible, with no distortion, so that the character of the instrument comes through. Acoustic guitar amps use transistors to minimise distortion.
Electric amps have standard 1/4-inch instrument cable inputs. Some electric amps have effects loops built in, with a preamp output and input, so that any signal loss from effects pedals can be minimised. Many electric amps also have two inputs, with different boosts, so that you can use active or passive pickups and still not overload the preamp. Acoustic amps usually have one standard 1/4-inch input, as well as an XLR input to plug in a microphone.
Electric amps are used to fill the hall with the guitarist's sound. Acoustic amps are usually used in much smaller venues, like coffeehouses or small clubs. Many times, an acoustic amp will be used as an onstage monitor, while the guitarist then runs the signal into the PA for amplification.
Acoustic amps are usually combo units, where the amplifier and the speaker are housed in one body. While electric amps are designed as combo units as well, many electric players prefer to buy a separate amp head and speaker stack, which allows them to match the output of the amp to a different type of speaker if they prefer, or to fill a large hall with sound.
Both acoustic and electric amps sometimes have effects like on-board chorus, delay and reverb built in. These effects can be used to create different sounds on songs. Some of the better acoustic amps also have an equaliser (EQ) section so that the guitarist can control different frequencies, which can be useful to both achieve a clean sound and notch down frequencies that might be creating feedback.