regulation of the rail voltages is provided by zener diodes. And a 3-pin 12 volt regulator is used to provide clean DC voltage to the heaters.
   Rather than using a plate resistor, Mr. Rozenblit has opted for using an active load in the from of an additional triode wired in an SRPP fashion. Feedback is taken at the output and relayed down to the grid of tube V3. The gain is set at +12 dB and the output impedance is a low 300 ohms.

Super Compact 150 Watt Amplifier
   Here is a conventional push-pull tube power amplifier with a few twists. The first of which is the use of EL509's in the output stage. These are the same tubes that are used in the Transcendent OTL amplifier, but here they are used as pentodes and are not triode connected. (The grid 2 voltage limit precludes connecting the grid 2 to the plate or to an ultra-linear tap on the output transformer primary.) A tube based regulator provides the voltage to the second grids. (This is a very good idea, as regulating the voltage to these grids effectively regulates the entire output stage of the amplifier.) An additional twist is the use of a Cathode Follower between the first stage and the Long Tail phase splitter.  While this circuit is not original, it is fairly rare, but should not be.

   The  use of a Cathode Follower will extend the frequency response of the phase splitter, as the low output impedance of Cathode Follower will overcome the Miller effect capacitance of the input of the Long Tail phase splitter. Secondly, if the value of the Cathode Follower's load resistor matches that of the first stage's plate resistor, the total current through both stages will remain constant, as the Cathode Follower works in anti current phase to the Grounded Cathode amplifier. (Unfortunately, these two resistors do not match each other in value in this amplifier. Additionally, before the heaters have come up to heat, the cathode of the Cathode Follower tube is subject to damage from the solid-state rectifiers bringing up the B+ voltage too quickly before the cathode is hot enough to emit electrons. If a cheap diode is placed, reverse biased, from the grid to the cathode, the cathode is safe, as anytime the grid voltage exceeds the cathode voltage by more than 0.7 volts, the diode starts conducting and until the cathode voltage becomes more positive than the grid. This diode is missing from the schematic and I would certainly ad it to the amplifier in spite of my recommendation not to modify any of the book's projects, as it should not have any effect on the sonic performance of the amplifier.)     

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