One possible implementation of the this two section approach is shown above. Here the first stage is a fairly straightforward two triode cascaded amplifier. The first triode(s) inverts the input at its plate, which in turn is inverted again by the second triode back to normal phase. The non-inverted signal is then given to a cathode follower which buffers the second triode from the added load imposed by the following stage and the feedback loop. The output from the cathode follower is then returned to the first triode's cathode via the two resistor feedback loop.
      At low frequencies, all of the resistance within the feedback loop is used to voltage divide the output signal deeply as it returns to the first triode's cathode. Thus the gain at these low frequencies is great, as a positive signal applied to the first tube's cathode subtracts from the total gain of the amplifier; thus the less signal returned, the greater the gain. But at higher frequencies, the feedback loop capacitor shunts away one of the feedback resistor's resistance and now the voltage division only partially voltage divides the output signal, thus greatly reducing the output at these frequencies, as more positive signal is given to the first stages cathode. This creates two gain plateaus: one below 50-Hz and one above 500-Hz, the latter being down -20 decibels relative to the former. This is the first half of the inverse RIAA equalization curve.

      The second stage is an inverting amplifier made up of a grounded-cathode amplifier cascading into a cathode follower. The feedback loop consists of only the 200k resistor and its shunting capacitor. At low frequencies, the input resistor (20k) and feedback resistor define the gain of the stage based on the ratio of their values. At high frequencies, the shunting capacitor's declining impedance shortens that ratio, which decreases the gain. At an infinitely high frequency, the capacitor's impedance becomes effectively zero and the gain falls to zero, not unity (1), but zero output. This is an improvement over the conventional single equalization feedback loop applied across a non-inverting amplifier, as the output should continue to fall with increase frequency, not go flat once unity gain is reached, which effectively results in a high-frequency boost.
    (To overcome this departure from the RIAA curve two approaches have found favor: do nothing, as the record itself has its own high frequency limitation, its own falling off with ever higher frequency function, which even if it did once have infinite frequency response, playing it once would scrape the highs off its surface; and add a fourth pole to the equalization network to help the output follow the RIAA curve beyond the unity gain point, usually this takes the form of a simple passive-RC-low-pass filter added to the preamp's output.)

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