Power scaling requires that the voltage supply to an amplification stage of an amplifier is reduced. Power scaling designs and kits have been given names such as VVR, VCB and VRM but equate to the same overall requirement of controlling high voltages via the combination of components such as MOSFET and potentiometers. More information about Kevin O'Connor work with power scaling can be found here. They have a number of different types of implementation based on the amp requirements and it's type of biasing i.e. In more recent times people such as Kevin O'Connor of London Power, Dave Zimmerman, Dana and Richie Hall of Hall Amplification have come up with different ways to modify power supplies in guitar amps to make the power output variable. Power scaling has been around for many years and has been implemented in different forms. This will result in a decrease in current flow and decrease in power output i.e. Unlike a master volume, where part of the signal is sent to ground or two out of phase signals are mixed to cancel each other out, power scaling controls the amount of voltage which is sent to the plates (anodes), screens (where applicable) and grids of the Power scaling can be applied to the power section, the whole amp or any stage in between depending Power Scaling, in the context of guitar amplifiers, is a method by which the overall volume can be reduced without impacting the saturated tone, harmonics and dynamics of a fully cranked amp.

Variable bias vs fixed bias guitar amp