EAR Yoshino 861

After years of research, development and day-to-day manufacture with the EL519 series of pentode tubes, Tim de Paravicini has come up with a new and exciting Triode configuration. Conventional triode connected pentodes have the second grid tied to the anode, which results in a halfway compromise between a pentode and a triode. This neither has the efficiency of the pentode, nor the linearity of the triode. Tim de Paravicini’s Enhanced Triode Mode (ETM) goes one step further, and creates a true, highly linear triode from a robust pentode tube.

Instead of driving the normal Grid One with signal, this is tied down to the cathode, and thus becomes an invisible, transparent element, and part of the cathode. Signal is fed into the tube’s Grid Two, and in this configuration, Grid Three has no effect – it can either be connected to earth, or left floating. The ETM behaves like a true triode and is in fact more linear than the majority of directly heated triodes. Compared with the latter, it has the additional advantage of being a tough, more robust tube, capable of much longer operational life.