Guitar Amp versus Keyboard Amp versus Acoustic Amp
A friend asked the question, “what is the difference between a guitar amp and a keyboard amp”? My simple answer was along the lines that an electric guitar amp plays a role in creating a sound for an electric guitar, while a keyboard amp just takes a sound, and makes it louder. This conversational answer was rather oversimplified. Also, I believe this is a question that many people might feel embarrassed to ask.
So, the more complete answer is: An electric guitar amp is designed to create a tone or sound for an electric guitar, which has no real acoustic sound of it’s own. An electric guitar amp might introduce levels of reverb, levels of distortion, or other effects to color the sound. Electric guitar amps are constrained by design to a limited range of frequencies, mostly focused in the mid-range, and do not reproduce the high and low ends of the sound spectrum very well. Electric guitar amps can be built according to one of three different technologies. Tube or valve amps employ vacuum tubes in the amplifier circuit and provide an authentic natural response. Solid state amplifiers replace the tubes/valves with transistors, or integrated circuitry. Modeling amps recreate the sound of classic amplifier families, and model the behavior of tube amps through various clever software modeling. The classification goes further in that there are different speaker sizes, cabinet configurations, combinations of speakers.
A keyboard amp on the other hand amplifies and delivers the actual acoustic sound. An acoustic guitar amp may include a pre-amplifier to boost the sound coming from the onboard guitar pre-amp, together with additional mid range frequency equalization controls, called notch filters, which can be used to manage the sound of piezo pickups.
Both keyboard amps and acoustic guitar amps cover the sound spectrum more completely, including the lows, mids and highs, and therefore reproduce more closely what you hear acoustically.