The 12AT7 is a miniature, high-mu twin triode designed for use as a grounded-grid radio-frequency amplifier or as a combined oscillator and mixer at frequencies below approx 300MHz. It's another very well known tube among guitar players. It has a much lower Gain output at 60, but what you lose in Gain you get back with more headroom, higher fidelity, and an increased current output. Because of their high fidelity they are also used in many tube microphone preamps, compressors, and recording equipment. They are also used in many organs. Because of their higher current you sometimes see them driving effects such as Tube Driven Spring Reverb in many guitar amps. Just like the 12AX7 tube, the 12AT7 has many different versions created for specific reasons, such as low noise and ruggedness.

The 12AT7 can also be substituted in 12AX7 gain stages where users are seeking lower gain response from higher gain positions in the preamp string. 

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