TUNG SOL 5751 (12AX7) gold pin. This 5751 is a replacement for any 12AX7 tube. The 5751 was designed as a "heavy duty" dual triode tube with similar specifications to the 12AX7. However, with a 30% profit reduced. That's why the 5751 is a fantastic way to tame distortion and shape the tone of an amp.