The design of the VA 1.0 is completely unique. Solid state transistor circuitry drives the valves. Specially designed solid state devices also monitor and constantly bias the valves, so that they are always matched to perfection. This makes the VA 1.0 the most user friendly valve amplifier available. There is no need to match valves, any valve may be replaced without having to change the whole set. Plus, bias control is automatic. Just switch on the VA 1.0, and play.