If you are looking to buy an amplifier to play blues guitar, it helps to know a little bit about the different types of amps available, and how they will sound.

Valves, tubes, transistors and solid state

You might well have heard of tube amps, valve amps, solid state amps and so on. But what does it mean?

To get the easy things out of the way first.. when we talk about amps, the word "tube" is short for "thermionic tube", while the word "valve" is short for "electron valve" - these two words actually refer to the same thing! The word valve is the general parlance in the UK and Australia, while the word tube is used more in North America. In the past two decades, as more and more guitarists have come onto the internet and started talking about gear, this has caused a great deal of confusion for newbies who read about "valve amps" and "tube amps" and wonder what the difference is.

Solid state and transistor are also words that mean pretty much the same thing.  A solid state amp is a transistor amp.  Transistors are a more modern technology, that is cheaper to mass produce, are less temperemental, run at much lower, safer voltages and has less parts to replace.

Valves and Tubes

60 years ago, valves were in most electronic devices, from radios, aeroplanes, televisions and even the earliest computers.  Decades later they aren't in much use for any of these things anymore, and it's easy to see why.  Valves need a high voltage to run, which can be quite dangerous, and to work properly they need to get very hot.  Being somewhat similar to a light globe, they also need to be replaced periodically. They also require the use of some very heavy transformers which adds to the cost and the weight of these devices.

So with all these disadvantages to the technology, why do they still put valves in guitar amps?  Well, put simply, valves sound great.  They have a warmth and a natural compression that you just don't get from a transistor amp.  They also respond well to being driven hard, having an overdrive character that is very pleasing and musical.  If you are interested in playing blues, the sound you are after will almost certainly require valves.

Does this mean you can't play blues guitar on a transistor amp? Well, not quite.  BB King is known to favour a Lab Series L5, which doesn't have a valve in sight.  If you are looking to have a pristine clean tone then a good transistor amp might be just what you need.

You may have heard these talked about before too.

A combo amp is so named because it combines the amplifier and the speaker in a single box.  A head on the other hand, has no speaker.  It needs to be plugged into a seperate cabinet.  One of the main advantage of a combo is that you only have one thing to carry around.  A head and cab will require extra trips to the car.  The head will be lighter than the combo though, and if you want to use a big cabinet then it will probably be easier to carry around.  A head and cabinet setup is also popular with a lot of players because it allows you to play with a closed back.  Why would you want to that?  Well, read on..

Open back and closed back speakers

If you are playing a combo, then it will almost always have an open back.  If you are opting for a head and cabinet, then you will be able to find cabinet that is either open, or closed.

An open back will be less directional and have something ofa bright and airy sound to it.  A closed back cabinet is darker and less trebly sounding.. they are also louder and more directional with the sound.

For most blues guitarists, an open back combo is probably the best bet for the sound you are after.  For players moving in a blues-rock or hard rock direction though, it might be better to opt for the closed back.  That said, many of the heaviest sounding Led Zeppelin parts were recorded with a small 5 watt supro combo amp.