VCB is a method for controlling the power supply voltages within a valve amplifier. By controlling this voltage, you can control the amplifier’s power output. VCB provides a continuously controllable voltage, and you can rotate a knob to get as much or as little power output as you like.
The reason why this is a popular upgrade for valve amplifiers is that you can get the amplifier’s natural power valve distortion at much lower room volumes. Just dial the voltage down and the amplifier’s maximum volume drops. VVR was designed and refined by Dana and Richie Hall of Hall Amplification. The Amp Maker version is called VCB, and this version, VCB1, is for cathode biased amps. It’s been successfully fitted to many amplifiers, from Champs, Deluxes, 18Wers, AC30s, etc.
Easy to build
There are several ways to implement VCB in a valve amplifier. See the build section for full details. On the 1-5 complexity scale that I use for amp kits, it would rate a 0.25. Allow perhaps an hour for planning and double-checking your cable runs and another 30 minutes or so for building the kit and wiring it in.
In fact, the hardest part is safe handling of the central component – the MOSFET. Unlike the sturdy old-fashioned valves inside your amplifier, the MOSFET is very easily damaged by static electricity.
VCB installation guide now available (click below to open PDF)