| 摘要 |
A circuit which allows for the simultaneous control of the bias voltages applied to the screen grids and control grids of output tubes while maintaining the ratio of said voltages, thereby providing a method for selectively varying a single plate characteristic (Power Output) of a tetrode/pentode vacuum tube. In the case of musical instrument amplifiers, it is a desirable effect to drive the power amplifier (output stage) beyond the point that said power amplifier is able to reproduce its input signal accurately, hence causing output distortion. Said point is known as the "Clipping Point". A clipping point is most usually achieved at high sound pressure levels which are uncomfortable and difficult to work under. By varying said voltages in the previously stated manner, one varies the clipping point accordingly, and therefore is able to obtain output distortion at variable sound pressure levels.
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