Cathode followers: Love 'm or hate 'm

Among tube designers, the cathode follower is always subject to debate. Most such discussions are initiated by perceived differences in sound quality, sometimes described as dull and lacking transparency, and Guido agrees that the classic cathode follower has a clear and substantial sound signature. Compared to other valve circuits, few measured results are available concerning cathode followers. However, offering low output impedance and the possibility for DC coupling makes cathode followers well suited to drive power triodes. Over the years Guido managed to optimize cathode followers to become more musically transparent. This article documents the distortion mechanisms in cathode followers and his measures to suppress them.