Fender Dual Showman Reverb Standard Retube Kit

These amps are one of the rare Fender amps that are fixed bias so the only way you can adjust it is to replace the final bias resistor with a value that gets the bias where you want it. This is why most players will simple mod it or have it modded to be adjustable bias.

If your amp is bias modded then all you need to adjust the bias is a bias probe and a multimeter or the Eurotubes "Pro One". All of these are are available in the "Related Products" tab.

You can use the Deluxe Reverb bias video for reference. We typically bias Twin Reverb amps between 35 to 40mA with the JJ 6L6GC's.

The video below explains the difference between bias probe types.