User manual

4.3 Microphonics and Bad Noises
The overall performance of pre-amp tubes is easily influenced by mechanical factors from
the outside. This would manifest itself by a sudden feedback sound with high pitch. The
input stage is especially suspect to this phenomenon. If one encounters microphonic tube
behavior, then the first tube should be checked as a rule. Pre-Amplifier tubes can also cause
hum or other bad noises, like crackling or ticking.