The CV5948 (commercially the ECF804) is a triode pentode designed for application in wide-band amplifiers and instrumentation. Wide band amplifiers require a large mutual conductance, and thus initial high gain, to allow feedback to broaden the bandwidth and flatten the pass-band, all at the expense of gain.
The triode anode is folded and stitched on one side. The copper grid support can be seen top and bottom.
The pentode is clearly a beam tetrode. The inner grids are framed by the bright beam plate.
Side view showing that the active part of the anode is only that facing the grids and cathode.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
