9 pin miniature preamp tube (Amplification Factor = 100). This is the ubiquitous Chinese 12AX7 with added selection. The gain is high and the American "Ruby Tubes" must be filtering out the noisiest ones. For more information about our 12AX7 tubes, see our tech corner article on 12AX7s.

Ruby tubes are sorted and selected for the maximum quality possible. The sorting process eliminates failures and ensures satisfaction.

12AT7 Preamp tube, Ruby brand

6550A-STR, Ruby brand, Power Tube