An even bigger mistake is to be oblivious to the input, ground, and output relations within a circuit. The two circuits shown below make the same mistake: they do not account for the differing needs of the top and bottom output tubes; thus, both circuits are terribly unbalanced. Unfortunately, these bad topologies are common in practice. If any excuse for their use is given, it usually is that feedback will straighten things out. (Another example of how relying on feedback breeds sloppy circuit design.)   

      A clean-performing output stage requires deciding on one basic output topology for both output tubes. In other words, both output tubes should function as grounded-cathode amplifiers (GKP), providing voltage gain and a high output impedance or as cathode followers (GPK), providing unity gain and a low output impedance, but at no times should a mix of these two fundamental topologies be used. Nor should feedback be relied upon to straighten a fundamentally bent output stage.

Split-load
phase splitter arrangements
     Four good arrangements and two bad arrangements are possible with the split-load phase splitter cascading into a series push-pull output stage. We have just seen one of the bad arrangements and below is the second.

     This amplifier, like the previous bad designs, is fundamentally unbalanced from its inception. (Only one load impedance can force the amplifier into balance: zero ohms, i.e. a dead short to ground. In this case, both output tubes see the same drive signal and both undergo the same current swings; in all other cases, not.)   

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