What is the Difference Between a Solid State Amplifier and a Tube Amplifier?

The two main types guitar amplifiers are solid state amplifiers and tube amplifiers. The difference between them, is characterized by how they amplify the incoming sound waves from the guitar pickups. The two types of amplifiers have very different sound qualities, and each has their own strengths and weaknesses.

Tube Amplifiers

Tube amplifiers have relatively simple electrical circuits that utilize old-fashioned valves (tubes) to amplify sound. The overall tone they generate is almost always described as “warm”. This warmth is very difficult, if not impossible to measure, which is perhaps why it is so difficult to emulate with solid state amplifiers. The tubes, or valves, are responsible for the pre-amplification of the signal, the distortion and tone, as well as for the power circuit.

 

The big difference in sound characteristics with tube amplifiers, occurs when the input signal is high enough to cause overdrive. The sound is then “clipped”; in the case of tube amplifiers, this clipping creates a very natural sounding distortion, which is harmonically pleasing.

Tube amplifiers need internal transformers to power the circuitry, this, together with the heat that the tubes themselves produce, make for possible overheating issues. Some guitar tube amplifiers have built-in fans for cooling, but the majority do not.

Tube amplifiers are much heavier than solid state amplifiers and they require regular maintenance. The tubes need replacing once a year or so, and the output-tubes need re-biasing every year or two. Tube amplifiers need to be played at high volume, to get the full, rich tone that they are known for.

 Solid State Amplifiers 

Tube amplifiers dominated the market until the 1970's, when more sophisticated electronic circuitry started being used for amplification, creating the first “high definition” amplifiers. These amplifiers used semi-conductors instead of valves to control the output of the sound signal.

Solid state guitar amplifiers have a much “colder” sound, mainly due to the harsh distortion that occurs when the incoming sound signal is clipped. Solid state amplifiers are cheaper, generally, due to the use of circuit boards and no need for heavy, expensive transformers. The distortion that occurs in solid state amplifiers, is often described as being “too sudden” and therefore harsher than that of valve amplifiers.

Solid state amplifiers are good for guitar playing in the following respects: they have a very quick response time to the input signal from the guitarist; the sound is very crisp and clear (as long as the input signal is not over-driven); the amplifiers are fairly robust and the components are not easily damaged when the amplifier is moved around.

Although there is less that can go wrong with a solid state amplifier, when things do malfunction, it is very difficult for the average guitarist to diagnose the problem, and inspection and repair of these units is potentially very expensive. Tube amplifiers can be diagnosed quite easily and tubes themselves are not difficult to replace.