If the direct connection layout is used instead, then the path to the negative power supply noise will be effectively severed. In the circuit below, a new path is created by connecting a power supply filter capacitor not output ground but to the negative power supply rail.

    Introducing this noise at the split-load phase splitter input ensures that its cathode will relay the noise faithfully to the bottom device. Amazingly, the interjection of noise also ensures that the top device does not see the noise. How can this be so? The phase splitter's cathode resistor sees the same noise signal at both its ends, thus it never experiences any current fluctuations due to that noise signal, and thus the plate resistor cannot reproduce the noise signal. As it sees a constant current draw from the plate. 

    The split-load phase splitter is marked by an extremely high plate impedance due to the presence of the large unbypassed cathode resistor. Whatever signal appears at the top of the plate resistor will also appear at the bottom of the resistor. If this signal meets an inverted version of its self, both signals will cancel. Thus if we superimpose the negative power supply noise on the input signal, the bottom output device will see the its required noise signal and the top device will see the null that results from the input signal being inverted at the plate canceling the in phase noise signal.
    Had the filter capacitor been connected to ground, the negative power supply noise would not be canceled at the plate and the output would polluted by it. The lesson here is that filter capacitor should not always be terminated into ground. (Some are not mentally flexible enough to grasp this and, unfortunately, they design most amplifiers.) 

    If we reverse the connections from the phase splitter, as in the circuit above, then a different strategy is required. The bottom device still needs to see the full negative power supply rail noise and the top device needs to see no noise. Both conditions can be satisfied by virtue of the bipolar power supply. If the phase splitter's cathode is noise free, the cathode resistor will see the full negative power supply noise signal, which will in turn create a current signal that the plate resistor will experience. This current signal
Creates an in phase replica of the negative power supply noise at the plate, which is then relayed to the bottom output device via the coupling capacitor. (This trick only works because the cathode resistor is not grounded.)

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