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Mid-Referenced Totem-Pole Amplifier

This circuit is a TCJ original and it has never been commercially offered. In this circuit, sporting positive and negative outputs rather than the usual hot and neutral, the load is never "grounded," as the two-resistor voltage divider splits the output signal and fixes ground at that point. The bipolar power supply is left floating and it moves up and down with the output signal in anti-phase to the connection between top tube's cathode and the bottom tube's plate.

Both triodes function in a modified input-signal-degeneration mode (a modified cathode-follower mode), as each output tube's grid sees only half of an externally applied perturbation to the output, as the signal reference lies midway between the top and bottom tube's cathodes. This configuration results in a higher output impedance than a pure cathode-follower connection would yield, which would relay the full magnitude of the perturbation to both top and bottom tubes. On the plus side, the drive signals for both the bottom and top triodes are now equal in magnitude (but in anti-phase) and both are referenced to ground, greatly simplifying the driver stage design. In other words, the driver stage does not need to be tied to the output stage.

This circuit delivers the exact same performance as the generic, simple circlotron output stage, but only requires one center-tapped power supply per channel; if the voltage differential between top and bottom cathodes is too great, however, it will need two separate heater power supplies.

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