Fast/Slow Rectifier Upgade
Select this option to upgrade a Classic series amp with twin rectifiers! This option turns the "Standby" switch into a 3-way toggle to tweak out the player's tone by selecting a modern, "FAST" rectifier, or a vintage tube driven "SLOW" rectifier. In the middle position the amp is in Standby, giving the player freedom to take breaks or switch rectifier modes without damaging the amplifier, tubes or speaker.
The Steamboat Classic 18 upgrade comes with one 5y3 rectifier tube, and the Classic 50 upgrade comes with one 5U4GB rectifier tube.