US Patent 7408401 Vacuum tube replacement device, circuit and system

A system is provided for a solid-state implementation of a vacuum tube replacement device. The system may derive power from a target amplifier filament supply. The system may include active or passive functions for noise reduction, voltage isolation, servo biasing, and other functions. The vacuum tube replacement device is pin-for-pin compatible with standard vacuum tube circuit pin configurations. The vacuum tube replacement device system architecture is equally useful for non-vacuum tube systems such as audio amplifier circuits.