Part Number: 12AT7
Function: Triode Vacuum Tube, Receiving Valve
Package: 9 Pin Type
12AT7 (also known in Europe by the Mullard–Philips tube designation of ECC81) is a miniature 9-pin medium-gain (60) dual-triode vacuum tube popular in guitar amplifiers. It belongs to a large family of dual triode vacuum tubes which share the same pinout (EIA 9A), including in particular the very commonly used low-mu 12AU7 and high-mu 12AX7.
The 12AT7 has somewhat lower voltage gain than the 12AX7, but higher transconductance and plate current, which makes it suitable for high frequency applications.