Understanding Vacuum Tube Guitar Amplifiers
Developed throughout the 20th century, vacuum tube amplifiers, otherwise known as tube or valve amps, are still at the forefront of guitar amplification.
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Vacuum Tubes
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Examples of power-amp vacuum tubes. Vacuum tubes convert heat into electricity. A glass casing houses a heating element next to a cathode and an anode, which are separated by a grid. The guitar signal enters the amplifier as a weak electrical signal, which is then passed through a series of vacuum tubes.
How Tube Amps Work
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The most important element that makes a vacuum tube work is heating up. Heat energy is converted to electricity, which is then added to boost the weak guitar signal. In most guitar amplifiers, there will be two sets of vacuum tubes; pre-amps and power amps.
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Pre Then Power
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The pre-amp valves, which are smaller, boost the signal a little, preparing it to be sent through the power-amp valves. It is while being passed through the power-amp valves that the signal is given a massive surge of power.
Sensitive and Temperamental
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Because vacuum amplifiers rely on being hot to function, allow your tube amp to warm up before playing. Be careful during transport, as the glass casings are very delicate.
Troubleshooting
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Never handle the tubes with your bare hands; the oils from your hand cause hot-spots that will crack, destroying the tube. A high pitched whine can indicate that the pre-amps are on their way out, whereas a low rumbling will point to a faulty power-amp.
Buying New Tubes
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Replenish all the tubes at the same time to ensure longevity. Amps are set at a certain balanced regular voltage, known as the bias. If your new set is different from your previous set, the amp will have to be re-balanced and have the bias reset.
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References
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- Photo Credit live music image by maxthewildcat from Fotolia.com vacuum tubes on white background image by Dmitry Rukhlenko from Fotolia.com
