WHY VACUUM TUBES

The output level of studio microphones under typical recording conditions contain peaks far in excess of what VU meters display. Everyone knows that, but the peaks, as measured with an oscilloscope, are really quite high, easily exceeding 1 volt! The tube or transistor used in a condenser microphone, or in a microphone preamplifier, often will be driven into severe overload by these peaks. The peaks are short, so the sound isn't grossly distorted-sounding; but the distorted peaks do affect what we hear. All preamps (and condenser microphone electronics) are overloaded by these peaks, but tubes handle it differently than solid-state devices.

When transistors overload (in a discrete circuit or in an OP amp), the dominant distortion product is the third harmonic. The third harmonic "produces a sound many musicians refer to as blanketed”. Instead of making the tone fuller, a strong third actually makes the tone thin and hard. On the other hand, with tubes (particularly triodes) the dominant distortion product is the second harmonic: “Musically, the second is an octave above the fundamental and is almost inaudible, yet it adds body to the sound, making it fuller”.

Tubes sound better because their distortion products are more musical. Tubes provide a more appropriate load to transducers. These are the fundamental reasons why tubes simply sound better.