away with exceeding the maximum plate voltage spec of V2, but beware of using small delicate tubes at too high a voltage.

A trick that works well when a V2 needs to support a very high plate voltage is shown in figure 4.9. The control grid and screen grid of a beam tetrode are connected together. This gives the tube a very high mu, usually well over 100 and has the plate voltage rating of the beam tetrode. If TV sweep tubes or transmitting tubes are used, this can be very high. Applicable tubes are: 807, 6AU5GT, 6BQ6GTB, 2E26, 6146, etc. Since these tubes are not characterized for this type of operation, I've found that the actual mu varies quite a lot from tube to tube, so

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