FREE EVERY MONTH Scrumpy ‘n’ Western issue 8 vol.5 THE TAILGATERS NOVEMBER ‘08 28 PHOTO BY PETE BROWNETT With <strong>over</strong> <strong>650</strong> <strong>live</strong> <strong>gigs</strong> <strong>listed</strong>
FREE EVERY MONTH Scrumpy ‘n’ Western EXTRA FACTS ABOUT AMPLIFIERS Or did you know Part one If you use an electric guitar or electro acoustic then you will be using an amplifier which will come in various sizes from a small 10 watt practice to anything larger!! This article is really to give you a better idea of what you are really using and my be of help <strong>with</strong> a bigger purchase in the future. An amplifier takes a tiny electrical current and turns it into a much bigger current that will move loudspeaker cones. The first devise that could do this was a valve, and the ‘amplification tube’ was patented in about 1906 (oddly enough by two people , who were working on the same idea but independently.) The early audio amplifiers were huge devices <strong>with</strong> each section of the circuit forming a separate unit in a rack. The first known electric guitar design dates back to the early thirty’s, but the first purpose-built guitar amplifiers appeared in America in the 1940’s and were modified from radio set circuits. Leo Fender had started ‘Fender Radio Services’ in the early 1940’s as Radio was the then modern technology of it’s day. The first guitar amplifier to use transistors, available to buy commercially was the Burns Orbit combo, made in Britain about 1963 (Burns being a top UK brand) The 40 watt combo sported a tremolo circuit and there were a number of variations, based on different speakers. At that time, this ground breaking design was more expensive than the valve combos on sale at the time! Where as today a valve combo will cost far more. Today guitarists spend a lot of time arguing <strong>with</strong> other guitarists whether valve amps are ‘better’ than the many modern designs that seek to emulate the valve sound. This could be a complete waste of time as for a number of reasons like better could mean to be far more reliable in use or a better range of tones and many other possible, undefined criteria. This could be down to a personal thing, but generally most top guitar players will use valve as a better sound. Even the term ‘valve’ is misleading, because they are NOVEMBER ‘08 29 used in very different ways, in different designs. As the name states, a valve really does regulate a flow in a valve amp, but it’s a flow of electrons, not water. Inside the valve is a cathode and a plate, <strong>with</strong> a grid in between. Electrons flow from the cathode to the plate. The grid in between controls the flow of electrons, hence the valve-like action. The cathode has to be warmed for this to happen, so there is a small heater at the bottom of each valve. This is what you are turning on when you put the amp into standby. Very small voltages applied to the grid cause big changes in the electron flow (current) between the cathode and the plate, that’s amplification. The voltages are determined by a variable input, an electric guitar! You might assume that when you’re not playing at all, the grid is at ov but this is not so. In a power valve, it is likely to be somewhere around - 40v. The precise voltage used varies from case to case and is called the ‘bias setting’. In a Class A circuit, the valve is never idle. The bias is set so that the valve is passing current at all times. The first known class A guitar amp is the Vox AC15, introduced in 1956. Class B amps can produce a lot more power than class A. They use two power valves in a push pull configuration or multiples of these pairs for higher powered configurations. One of the pair handles the positive side of the wave form, while the other handle the negative. The bias is set so that the valve is idle in between times. In reality, this arrangement doesn’t sound so good because there is unwanted distortion of the waveform at the cross<strong>over</strong> point where one valve stops working and the opposite half of the pair kicks into life. We will continue next month, meanwhile if you are looking to purchase a new amplifier remember guitars do have a sound of their own, take your guitar <strong>with</strong> you when buying a new amp, for you could try out in the shop using one of theirs, get home and find you are not satisfied <strong>with</strong> the sound!! A good music shop will want you to buy what you are looking for, since there is the repeat business, of strings etc.....
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