The evolution of the amplifier, from the triode to the transistors

The triode is considered one of the twenty most significant inventions in the history of mankind and gave rise to the first tube amplifiers. Subsequently, the world of amplifiers evolved and some models with transistors were born, leaving aside those with valves, since they were cheaper.

Lee De Forest and the invention of the triode

This American engineer and inventor invented the triode in the early 20th century, which was made up of a platinum grid, anode, and cathode. All this was enclosed in a kind of partially empty light bulb.

Thanks to this invention, Lee De Forest is considered the father of electronics. From then on, triode vacuum valves were born, which were basically the same, but inside the bulb there was no air, much less any type of gas. This prevented the filament or cathode from burning quickly.

This creation allowed that with a weak voltage, a greater current strength will be created for audio equipment. This is how vacuum triodes began to be used in high-quality amplifiers, gramophones, televisions, etc.

The triode was patented by Lee himself in 1906 and was initially called a device for amplifying weak currents, until it was later abbreviated as Audion.

His triode was used as a receiver of wireless signals for a long time, until in 1912 it was discovered that it could serve to amplify radio signals.

However, one of the most successful early inventors using the triode as an amplifier was the American Fritz Lowenstein. This man patented a device called the Telephone Relay on April 24, 1912. His invention was widely used in amplification, so that in 1913 improved versions with higher vacuum appeared through the American Telephone and Telegraph Company, which acquired the Audio rights.

Also, we mentioned that triodes were used as continuous wave transmitters, replacing the old damped wave transmitters. From there comes the transmission of sound by amplitude modulation, that is, the famous AM radio signal.

Another contribution that the triode brought was transcontinental telephone communication, since from this new technology more powerful repeaters were created, based on vacuum tubes with 3 electrodes. Previously, a phone call was no more than 1,300 km away, but now the world changed drastically with signal amplification through triodes.

Responsible for this breakthrough was Bell Telephone, a company that had also bought the rights to Audion. On January 25, 1915, the first transcontinental telephone line was established.

Much later, tetrodes and pentodes appeared, which improved some deficiencies of the triode. Basically, they offered the same advantages, but their prices were a bit higher.

Vacuum tubes based on Lee De Forest’s triodes were made with a design similar to light bulbs, as they could be changed when the cathode burned out. The difference is that they enter the socket under pressure and not by screwing them. This is still the case, since the filaments or cathodes get very hot and are in constant use inside the equipment. For this reason, many people prefer to buy sound amplifiers with other technologies, because vacuum tube amplifiers require frequent maintenance, depending on the type of use you give them.

However, triodes are still used in high power equipment, as today’s amplifiers do not offer the same capabilities. For example, many radio transmitters and industrial heating equipment use vacuum valves among their main components.

Transistors and valve displacement in amplification

Starting in the 1960s, vacuum tubes or valves were losing fame, due to the appearance of the silicon transistor. This invention amplified sound by changing the voltage of the audio input, using semiconductors. Several companies preferred transistors because they were much smaller and lighter, as well as being energy efficient.

Similarly, transistors were easier to manufacture and therefore cheaper. This allowed the creation of self-powered equipment accessible to various social classes.

At the moment, solid-state transistors are most widely used, for example bipolar junction transistors, which have three semiconductor elements.

Bipolar junction transistors are formed by two PN junctions in the same semiconductor crystal, forming 3 regions, emitter, base and collector. Its function is to increase the current and decrease the voltage, so it is very useful in various applications, especially amplification.

Also, at this time MOSFET transistors have been widely used, which are used for both digital and analog electronic circuits. This type of transistors are widely used in digital circuits, because they do not need resistors, so they save space on the board. In addition, its consumption in static mode is very low, which is why MOSFET transistors are widely used in CMOS circuits. Even its switching speed is high, and can be measured in nanoseconds.

However, transistor amplifiers did not offer the same sound fidelity as valves, because they emitted a distortion called TIM that bothered the most demanding ears. This phenomenon was discovered by Matti Otala in 1972 and through studies carried out later it was possible to eliminate the TIM from the amplifiers. For this reason, there is no need to fear when buying a transistor amplifier, but if you are looking for a specific sound for your electric guitar, perhaps the tube amplifier will be of great use to you.

For their part, transistor amps tend to offer more portability for your live performances, since most of them are lighter. In this way, the answer about which sound amplifier to buy will largely depend on your preferences and requirements.