GE Vacuum Tubes 6AS7GA And 5U4GB, Set of 2Condition:* Used, Sorry, Unable To Test. As Pictured.Additional Notes:* GE 6AS7GA Originally used as a regulator tube in power supply, and in projection tv booster scanning applications. These tubes are excellent for use in OTL amplifier output stage.* GE 5U4GB Rectifier Vacuum Tube. Most commonly used in guitar tube amps and home audio tube amps.GE6AS7GA 5U4GB