The 12AX6 is a 9-pin miniature, low voltage double triode vacuum tube (or valve) rated at 12.6 V and 550 mA with a heater current requirement of 1.95 A. The triodes are typically used in parallel and its frequency response range is up to 100 kHz. It is primarily used in the pre-amp circuit of audio amplification, as well as in some high-fidelity phono stages.