The moral
     The load impedance is part of the circuit and to assume that it isn't can only lead to a misunderstanding of how the circuit functions. For example, a load impedance of 1-ohm leaves only the intermediate resistor's value plus 1-ohm as the bottom triode's loading impedance, hardly a great constant current source in even the most liberal view.

The sub-circuits
     Let's take apart the SRPP and then we will put it back together. The constant-current source/cathode follower view of the SRPP breaks the circuit into two sub-circuits: a grounded-cathode amplifier and a cathode follower. Both circuits are easily wed in the schematic below. Each sub-circuit works into a 10k load. The result is an amplifier circuit that exhibits a good amount of gain and a low output impedance. (An added feature of the compound circuit shown below is the constant-current draw for the entire circuit.)

    Compound amplifier  made up of a grounded-cathode amplifier and a cathode follower

              Bootstrapped compound amplifier 

      In the above schematic, we see a further connection between the first stage and the second stage via the additional electrolytic capacitor. This capacitor relays the output of the cathode follower to the top of the grounded-cathode amplifier's plate resistor. Two effects result from this modification. The first is that the grounded-cathode amplifier now sees a much higher load impedance, despite the halving of its plate resistor. How is this possible? The cathode follower's output is in voltage phase with the grounded-cathode plate movements.

    Grounded-cathode amplifier and cathode follower 

    Transforming these two circuits into an SRPP only takes a few steps. The first goal is to further the connection between the two sub-circuits, as in the compound circuit, the grounded-cathode amplifier receives no stimulus from the cathode follower, that is the first stage is not influenced by a variation in the load impedance that the cathode follower stage might see.

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