Valve preamplifiers use triodes or low-noise pentodes (EF86). In addition, there were some examples of beam tetrodes designed to work in-place of pentodes. Both fidelity and efficiency exceeded those of the available pentodes of the time. The same principle was applied to other types of multi-grid tubes such as pentodes. Each stage used a Class B amplifier arrangement of EF8s, special low noise, "aligned-grid" pentodes. A MHz response could be achieved with two pentodes and six diodes per cell. In technical terms, JJ produces triodes, beam tetrodes and power pentodes. The anode characteristics of these tubes are very similar to pentodes. Tube computers primarily used triodes and pentodes as switching and amplifying elements. For pentodes, it is higher, about (5-7)/"g". While they are not strictly pentodes, their overall electrical behavior is similar.