The first electronic amplifiers used lamp technology, before moving on to the bipolar transistor. Today there are always tube amplifiers, but the majority of units produced using the transistor, bipolar or FET. One advantage of the transistors is their small size makes it possible to produce power ICs, where all the amplifier circuit is grouped into a single component. One difference between the lamp technology / transistor is the possible production of odd harmonics by the transistors, making the reproduced signal less pleasing to the ear than the output from the lamps, which are the even harmonics to be produced. Nevertheless, the field effect transistors (FET) share this benefit with the lamps.

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