Why do Valves sound better?
Valves can perform as a amplifier, generally they work in
pairs, one for amplifying the positive half of the signal, the
other amplifying the negative half. Valves are matched to each
other by a bias control with-in the circuitry of the
amplifier, if they are not matched properly the result is what
is known as crossover distortion.
Crossover distortion occurs where the positive and negative
halves of the sound wave do not match up, this grossly affects
small sound waves, whereas the effect is not as noticeable
with large sound waves. Therefore crossover distortion is
usually only noticed when a valve amp is being used at low
This is not the reason why valve amps sound better than
transistor amps when they are overdriven.
When an amplifier is overdriven the top section of the sound
wave is “clipped”. This changes the character of the sound and
so the character of the sound is determined by how the
particular amplifier behaves when it goes into clipping. When
a valve amp clips it tends to change the sound wave in a
smoother and more natural way, A transistor amp tries to
amplify the wave past the limits of its head-room and then
drops back down resulting in a more ragged sound wave shape.