The PP500 phono preamplifier, built around the JRC4580 op-amp, originally uses 3.3 kΩ resistors and 4.7 µF capacitors in the feedback network. While this design is stable, it can result in a lower output level when used with medium-output MM cartridges such as the Audio-Technica AT3600L.
To increase the gain and improve the low-frequency response, a parallel RC modification was applied. In this case, a 1.5 kΩ resistor in parallel with the original 3.3 kΩ resistor, combined with a 10 µF capacitor in series, was added. This effectively adjusts the feedback loop, increasing the overall gain while maintaining the low-frequency cutoff around 10 Hz, ensuring proper bass reproduction and RIAA correction.
After this modification, the PP500 sounds much louder and clearer, with a stronger, more dynamic signal. The midrange is richer, highs remain clear, and the bass is slightly more pronounced, providing a fuller and more engaging listening experience.
This approach is non-invasive and reversible, requiring only the addition of a few components to the existing feedback network, making it an ideal upgrade for PP500.
Parts needed: 2 resistors 1.5kΩ and 2 capacitors 10µF/50V .
