Nordost QBase QB6 Mk III AC Distribution UnitQBase QB6 Mk III The essence of the QBASE concept is a straight line AC distribution path, combined with star earthed topology for connection to a clean ground. By eliminating any form of in line filtering or active circuitry Nordost maintain the lowest possible AC supply impedance, while a tiny lift in the earth impedance of all but one of the output sockets routes the signal grounds directly to the centre of the star and the clean earth terminal.