The 6SA7 is a medium-mu twin triode vacuum tube designed for use in audio amplifiers and receivers. It was introduced in the 1940s and 1950s to replace the similar 6SQ7 tube as a more reliable alternative. It is rated for an amplifier plate current of 30 mA and its maximum plate voltage is 250 volts. The 6SA7 is a short-pin base tube that features a medium sharp-cutoff characteristic and a very low mutual conductance. It is notable for having very low hum and microphonics. It is used in the output stages of cathode-follower and single-ended amplifiers. This vacuum tube can also be used in low hum/low noise voltage amplifiers and low-voltage DC amplifiers.