The transistor has been around for over 65 years now, and solid-state technology must be considered mature. Further developments are likely to be evolutionary in nature, such as size reduction, rather than revolutionary. This is just the nature of innovation, a point of diminishing returns for a given technology. Radically new ideas for solid state amplifier circuits are unlikely.

The triode vacuum tube has been around for 90 years and the beam power tube for 61 years. So, vacuum tube technology and circuit design is also quite mature. Further major developments are unlikely. In fact, the improvement of modern vacuum tube amplifier performance over units from the 1950s is due primarily to changes in other components, such as capacitors and resistors, and attention to detail.

So, today when we compare a solid-state audio amplifier with one using vacuum tubes we are observing a showdown between two very mature technologies. All of the improvements in auxiliary parts are available in both types of amplifiers. And, lo and behold, the vacuum tube still produces superior sonic performance.

What accounts for the tube’s ability to survive and dominate the modern high end audio world? Many would say that it is because the tube produces a pleasant distortion. However this is just not the case. A well designed tube amplifier can produce vanishingly low levels of measured distortion (.01% and less is easily obtainable in preamplifiers) and extremely wide frequency response. The small amount of distortion produced in a tube circuit is mostly second harmonic, which is the type most easily disregarded by the ear.

For those who feel that the transistor represents better objective science, consider this: Both the tube and the transistor have parameters known as stray capacitance. That is, just by physically existing there is unwanted capacitive coupling between various elements of the devices (ex: plate to grid, collector to base). These can not be avoided. In essence there are several small capacitors contained in each tube or transistor.

In the vacuum tube the dielectric for the stray capacitances is nothing, a vacuum. This is the finest dielectric known, having far and away the lowest losses and least dielectric absorption (the way in which capacitors color the sound by reradiating stored energy).

In the transistor the dielectric is silicon, germanium, etc. In other words, using each transistor is essentially as bad as sprinkling a few ceramic capacitors in the circuit. Given a choice, no audiophile would allow even polyester caps in the audio signal path, let alone ceramics. Add to this the fact that transistor design typically uses 200% to 500% more active devices than tube circuits do and it becomes readily apparent why transistor amplifiers display strange subjective characteristics, particularly at mid and high frequencies.

There are many other technical ways in which the tube is scientifically superior to the transistor. They are sonically superior as well.

Isn’t it time you listened to tubes?