12AT7

The 12AT7 (ECC81) is a medium-mu (mu ~60) dual triode designed for VHF applications, with lower plate resistance (~11k ohms) and higher transconductance than the 12AX7. In audio it serves as a driver tube, phase inverter, or anywhere moderate gain with better current delivery is needed than a 12AX7 can provide. Its lower plate resistance makes it superior for driving capacitive loads and long interstage connections. The 12AT7 is also the standard reverb driver and effects loop tube in guitar amplifiers, where its current capability matters more than raw voltage gain.