Tubes: the Basics

Tubes, or valve amplifiers, are audio processing devices praised for their unique sounds. People associate them to the vacuum tube components they contain. The first electronic amps used vacuum tubes. The combination of an electronic guitar with a tube amp is a perfect example, for it revolutionized the peculiar guitar sounds.

Tubes: How They Work

Tubes need electricity to work appropriately. An electron, known as a negatively charged subatomic particle, will fly through space if attracted by a sufficient positive charge. In a vacuum, a magnetic field deflects electrons that flow from a heated metal element (the cathode) and are pulled toward a positively charged element (the anode).

Tube Distortion

Tubes are capable of distorting when you push them to the edge, which then results in a natural sound. Producers often describe the tube sound as warm and rich. The sound generated might be due to the nonlinear clipping. This can happen either with its amplifiers or because of the higher levels of second-order harmonic distortion.

Valve amplifiers have more sound distortion than solid-state amplifiers, but experts consider its second-order one. Listeners perceive a second-order distortion, aka harmonic distortion, as natural and pleasant rather than artificial. The second-harmonic distortion is exactly the same note, an octave above or more than an octave above. For example, the Apex Aural Exciter produced harmonic distortions. These made it a popular for both recording and broadcasting around 1970.

Tube Amplifiers

In musical performances, tube amplifier distortion produces a harmonic effect that increases as sounds get louder. Instruments generate a more harmonic effect as they artist play louder or hit them more strongly. As notes decrease, the percentage of harmonic content tends to drop. Tube amplifiers mimic this effect. A good tube amp increases its distortion within a one-million-to-one power range. 

Tube power amplifiers sound their best at the volumes that are frequently enjoyed. In contrast, solid-state amps measure and sound their worst at low levels. Also, solid-state amplifiers perform best at close to their maximum output levels, where no one ever actually plays them.