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Six Basic OTL Topologies
If you choose to use identical output stage devices, whether they be NPN transistors, N-channel MOSFETs, triodes, or pentodes, then there are only six ready ways to equalize the drive voltages to the devices in an OTL push-pull amplifier. Of course, there are an infinite possible embellishments on these fundamental topologies. However, seeing the same basic pattern in a multitude of particular circuits is the basis of understand electronics.
Some can't. the mystic refuses to generalize: grass is not seen, but a million individuated living plants regale his eyes. Many, if not most, audiophiles believe that changing a coupling capacitor's brand results in creating a wholly new topology. This failure (or refusal) to generalize is laudable in the viewing other people, but laughable in the attempting to understand how an amplifier works.
Of course, this begs the question: why would we want to equalize the drive voltages to the output devices? The answer is simple: we do not want a grossly distorted output, which is the result of an unbalanced drive. A key point here is that a balanced input signal does not necessarily achieve a balanced drive for the output stage. (To make this point, let's stick with conventional transformer coupled push-pull amplifiers for now.) For example, if dissimilar output tubes are used, say a 6V6 and KT88, then a perfectly balanced signal would result in a distorted output, as these very unmatched output tubes require a differing grid voltage swing to develop a balanced plate swing. In other words, the only time we need a perfectly balanced input signal is when we are using perfectly balanced output tubes in a perfectly matched configuration.
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