There are four types of guitar amplifiers: Solid-state (analog), Tube, Modeling (digital), and Hybrids.
Solid-state Amps: These amps are called solid-state because they use transistors for their preamp and power sections instead of tubes. They are very reliable and seldom need repairs. They often have a very clean tone, although many come with "distortion" channels also. These amps are popular with players looking for a sturdy, reliable touring amp.
Tube Amps: Tube amps preferred by many guitarists for their warm, fat tone and "organic" distortion. Tube amps usually sound louder than solid-state amps of the same wattage and have a definite "feel" that you dont get from solid-state amps. Most tube amps have separate channels that can switch from clean to distorted tones instantly. Tube performance can deteriorate over time, so tubes need changing occasionally.
Modeling Amps (Digital Amps): Modeling amps use digital processors to simulate the sound of old-fashioned tube technology. Using software that "models" the sound of tube amplifiers (and cabinets), these amps put the sound of numerous amps in one box. Modeling amps are programmable, and often have built-in digital effects such as delay, chorus, etc. Some include digital or analog outputs with speaker simulation for going direct into a recording interface or PA system.
Hybrid Amps: Combining the best of each type of amp into one package, these amps use an actual tube in conjunction with the solid state power section of their amps. Marshall Valvestate amps use tubes in the preamp section and solid state circuitry in the power section to create a tube tone without requiring the use of power tubes.
Buying used guitar amps is a great way to save money on your amp. These are great quality and allow you to find the sound you are looking for.
The first electronic instrument amplifiers were designed for use with electric guitars. The earliest examples appeared in the early 1930s when the introduction of electrolytic capacitors and rectifier tubes allowed for the production of economical built-in power supplies that could be plugged into wall sockets. Consequently portable vacuum tube amplification equipment was no longer dependent on heavy multiple battery packs for power. While guitar amplifiers from the beginning were used to amplify acoustic guitar, electronic amplification of guitar was first widely popularized by the 1930s and 1940s craze for Hawaiian music, which extensively employed the amplified lap steel Hawaiian guitar.
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