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4.2 Pre-amplifier Tubes
The pre-amps are equipped with 12AX7 tubes in all positions. The pre-amp tubes
are not designed to produce high power output. Therefore, their life expectancy is
much higher than that of the power amplifier tubes.This is not to undermine their
utter importance in overall sound and response ofthe amplifier. Also, annoying
defects like crackling noises and low dynamics are directly related to defective pre-
amp tubes. Like all other tubes, 12AX7 tubes come in many different gain stages,
and offer a wide variety of tonal behavior. Our choice for production was made to
ensure a wide variety of tones, with low noise and good reliability.
4.2.1 Microphonics and Bad Noises
The overall performance of pre-amp tubes is easily influenced by external
mechanical factors. Malfunction in these external components will manifest
themselves by a sudden, high-pitched feedback sound. The input stage is especially
suspect to these phenomena. If one encounters microphonic tube behavior, then
the first tube should be checked as a rule. Pre-Amplifier tubes can also cause a
hum or other bad noises, like crackling or ticking.