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October 

Page 18

Copyright © 2003 John Broskie    All Rights Reserved

In Conclusion

We have seen how the “circlotron” amplifier is only one topological variation in a family of similar topologies and that it is functionally identical with the totem-pole variation within that family that places its signal-reference point between the output and “ground.” Neither amplifiers are single ended in design, nor necessarily class-A in operation, nor do they defy the laws of physics; they are, in fact, merely generic building blocks that might be used in the designing of a brilliant or mediocre amplifier. With any of the topologies we have covered here, the hard work remains: figuring out how to exploit virtues and diminish liabilities. For each topology a different set of possible schematics exist. Deciding which schematic should be built requires work, weighing positives against negatives. Those looking for free rides will have to look elsewhere.

So will this be the last article on the “circlotron” amplifier? I doubt it, as I can imagine covering the many possible ways to configure the driver stage. For example, on page 7, two schematics were presented to illustrate how the vertical center-referenced push-pull amplifier could be attached to a phase splitter stage in a way that ensured a good PSRR figure, conforming to the Tube CAD Journal’s Audio Aikido set of techniques that use power supply noise to lower power supply noise at the output. Many more arrangements are possible.

(For a detailed explanation of how the modern “circlotron” works, click here to download a PDF of what I have found to be the best textbook explanation of the horizontal push-pull amplifier in a grounded-cathode configuration.)

                                        //JRB

Tube CAD does the hard math for you.

52 tube circuits in all: 

 

Four variations on each of the following circuits: cascode, cathode follower, common-cathode amplifier, differential amplifier, grounded-cathode amplifier, grounded-grid amplifier, I-to-V converter, long-tail phase splitter, plate follower, push-pull, split-load phase splitter, SRPP (totem-pole) amplifier, and White cathode follower.

 

Let Tube CAD figure out the gain, the output impedance, the PSRR figure, the bandwidth, plate dissipation, and maximum output voltage swing.

 

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