View Single Post
Old 06-26-2008, 05:39 PM   #15
Gremal Gremal is offline
Blu-ray Samurai
Gremal's Avatar
Feb 2007

VAC's Kevin Hayes is a wonderful resource for the science of tubes. He's been published in Scientific American and elsewhere. This is a cool explanation of tubes vs transistors on VAC's website.

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.

Last edited by Gremal; 06-26-2008 at 05:43 PM.
  Reply With Quote