The tube has exceptionally high power gain and a transconductance of 50000 micromhos. As such, the 4CX1600B requires care to obtain the expected performance. However, there are some sophisticated design features which will be discussed in principle. It is machined to present four annular cavities facing the center of the tube. Their function represents the most important difference between the '1600 and other external anode tetrodes.
All tetrodes share a disadvantage.
At the point where the instantaneous plate voltage drops near or below the screen potential, the screen attracts more of the cathode current. The cathode current is then reflected in a higher screen current reading. At this same point, the plate current is at maximum and more secondary electrons are produced. These electrons are attracted to the screen. If there is no design provision to circumvent or decrease the effects of secondary emission, the instantaneous low plate voltage always will produce heavier screen current.