Amplifiers with a tube at the input - sexy look and delicious sound.
Tube at the input provides a combination of two important properties - low noise and high linearity. Win-win. We run selected tubes (6DJ8, 12AU7) at relatively low plate voltage - the rails of our amplifiers may vary between +/-50V and +/-75V.
6.3V AC power source is required for filaments heating (roughly 300mA per tube).