Medium-Mu twin triode for use in preamplifier and driver circuits.
The 12AU7A is a miniature medium-mu twin triode intended for service in radio and TV receivers or in audio amplifiers. The tube is suitable for use in a variety of stages, such as general-purpose amplifier, phase inverter, oscillator, or multivibrator.

The 12AU7A tube type is equivalent to the 12AU7 & ECC82 tube. As compared to the 12AU7, the12AU7A exhibits a lower micro-phonic output.