The remaining four good designs divide into two groups: amplifiers with both gain and high output impedances and amplifiers with both unity gain and low output impedance; basically, grounded-cathode amplifier based output stages vs. cathode-follower based amplifiers. Which style is better? It depends on what you want accomplish: do you need more voltage gain or do you need a low output impedance? If you plan to wrap a feedback loop across the entire amplifier, then it is a wash between the two styles (as long as the loop is short), as the gain version gives more fuel to the feedback loop to lower the distortion and output impedance of the output stage and the unity-gain, low-output impedance version needs less feedback to bring its output in line.

    Reversing the connection to the phase splitter relays the output to the bottom triode, which inverts this signal at its plate, thereby providing 100% degeneration of its gain into the output. In other words, the bottom triode has been transformed into a cathode follower, while the top tube remains a cathode follower, as it now sees a fixed input signal.

     Retaining the same connection to the phase splitter, the following example eliminates the bootstrap capacitor and directly connects to the cathode side of the phase splitter. This connection results in the amplifier reverting to a pair of grounded-cathode amplifiers with their voltage gain and high output impedance. Only the bottom tube sees the effect of this connection to the output, as the signal from the output is relayed to the plate resistor through the phase splitter's cathode resistor and the plate resistor. The top tube still sees a fixed signal at its grid, as the phase splitter's cathode is forced to follow its grid. If this does not seem to make any sense, try to examine the resulting current flow through the phase splitter's tube when the output swings up or down.

     The amplifier shown above makes use of a bootstrapping capacitor to relay the output to the phase splitter's plate circuit, effectively eliminating any degenerative feedback between grid and cathode. Without this feedback mechanism, the top triode works just as much as a grounded-cathode amplifier as the bottom triode, providing voltage gain and high output impedance. 

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