History Of The Amp: Solidstate

Solid state refers to semiconductors (such as a transistor), its name merely means that there are no moving parts within the component.
Solid state components have revolutionised the world as we know it… however its introduction into the guitar amplifier during the 60s did not have the same impact.

A solid state amp offered many practical advantages over a valve amp. Some of which are…
1) Lower Cost
2) Lighter Weight
3) Higher Quality Consistency
4) Less Maintenance
5) Higher Durability

Although a solid state offered many practical advantages, it fell short in the category that mattered – sound. A solid state amp was capable of providing a clean guitar sound… but it struggled to produce the distorted sound a valve amp did so well.
Early solid state amps produced a harsh and cold sound (compared to valve’s smooth and warm). It had a limited dynamic range where the signal would be clipped if overdriven (producing an unmusical spitting sound). As a result, many guitarists did not abandon their valve amps for the practical advantages solid state offered.

However to be fair, solid state was not a complete disaster. It produced clean sounds very well, and some solid state amplifiers, such as the Roland JC-120, are regarded to be one of the best at providing a clean sound. 
As for the distortion, perhaps the sound of the solid state was merely introduced at the wrong time as during the late 80s / early 90s, certain guitarists used distortion which was sonically similar to the type solid state produced. (Although there are other reasons to explain why this occurred).
Interestingly though, solid state has always been regarded as inferior because it could not accomplish what valve could at the time. At no point was it marketed as an amp which could provide a different guitar sound. In the eyes of the guitarist, valve has always been the sound of the guitar.

As valve continued to dominate, many amp manufacturers did not give up on solid state. Due to its practical advantages, it became the choice technology for any type of budget amplifier.

One of the breakthroughs for solid state was Marshall’s Valvestate range. The Valvestate (introduced 1991, I believe) was designed to overcome the problems of solid state by emulating valve sounds.
In order to accomplish this they used a hybrid technology of both valve and solid state. It was a tremendous success. Here was an amplifier which combined the best of both worlds. The next step was to see if solid state could accomplish the task on its own.

As technology continues to improve, so does the quality of solid state.
Today, I would say that most solid state amps do a very good job at emulating valve. It is not perfect, but is constantly improving (I would even say that most guitarists may not be able to distinguish between a valve amp and a good solid state one if blind folded).
However solid state is still suffering from it’s history and continues to be regarded as inferior. Perhaps it will never be seen as better, because just as its quality has improved, the amp market has founded a new type of technology - digital…