9 pin miniature preamp tube (Amplification Factor = 100). This is the ubiquitous Chinese 12AX7 with added selection. The gain is high and the American "Groove Tubes" must be filtering out the noisiest ones. Great chiming tone with sweet, warm midrange excellent for Marshall® and Fender® amps. Smooth distortion characteristics and one of the highest-output preamp tubes in the GT 12AX7 line, with very consistent quality For more information about our 12AX7 tubes, see our tech corner article on 12AX7s.