Accordingly he completely bypassed the ‘conventional’ circuits, most of which use classic valves such as the 300B, 211 or 2A3, and based his design on his long-standing favourite output valve, the EL519. As conventionally connected that valve is a pentode, but Tim’s contribution was to invent a new connection which operated it as a triode, a connection he dubbed Enhanced Triode Mode, or ETM for short (the name highlighting the analogy with Enhancement Mode MOSFETs). Normal triode-connected pentodes have the screen grid connected to the anode, but Tim turned things upside down and connected the control grid to the cathode, using the screen grid as the input. This turned out to give better linearity, higher power rating and much better reliability than alternatives, and the 859 went on to become a classic amplifier, winning plaudits throughout the world. Its sound, a blend of the classic valve virtues of clarity and openness with modern low noise and freedom from ‘mush’, clearly set it apart from the competition and it has had a longer production run than almost any other such model.