5842
Dual Triode · IHT · 9-pin Noval · 1956
“Spectacularly fast.”
Medium-gain dual triode for driver and line stage applications
The 5842 (417A) is a Western Electric frame-grid triode designed for wideband amplifier and carrier telephone service, with extremely high transconductance (~25 mA/V) and a mu of ~43. It is one of the most linear small-signal triodes ever manufactured, with bandwidth extending well into the MHz range and distortion figures that rival solid-state devices. The tube demands careful layout due to its high transconductance and tendency toward oscillation if improperly decoupled. Genuine WE 417A/5842 examples are expensive but remain in reasonable supply from military surplus, and the tube rewards careful circuit design with exceptional transparency and resolution.