12AX7

"Top choice for gutiar/bass amp application with all the right ingredients. Excellent tonal balance, harmonic content, low noise floor, and low microphonics.
The tone is more vintage sounding, and also does very well in audiophile application.
The 12AX7-EH tube has a nice balanced sound, a very low noise floor and excellent performance in terms of microphonics.
The lack of microphonics is due in part to the return of a shorter plate structure and better materials."