Gramophone Pre-Amplifier Circuit with RIAA Response Curve


The following figure shows the circuit diagram of common Recording Industry Association of America (RIAA) pre-amplifier. The RIAA has developed the recording standard of response curve for any recording. It is developed to optimize the gramophone recording response for lowest signal-to-noise ratio for gramophone technology. The tape recording response is not linear, therefore the pre-amp for gramophone playback pickup should have such response which restore the original response, a flat response of played back signal.

Gramophone Pre Amplifier with RIAA Response Curve

Gramophone Pre-Amplifier with RIAA Response Curve

LM833 from National Semiconductor is recommended for the op-amp, however any low noise op-amp will works as well. In the figure above you see two types of the circuit. The first one is non-inverting, and the other one is inverting. In the non-inverting circuit, the 47k resistor shunts the input signal provide damping for the moving magnet phone cartridges. The input also shunted by a capacitance equal to the sum of the Cp and input cable capacitance. This resonates with the inductance of the moving magnet cartridge around 15kHz-20kHz to determine the frequency response of the transducer. Cp should be carefully chosen when a moving magnet pickup is used so that the total capacitance equals to the recommended load capacitance for the cartridge. (Source : National Semiconductor Application Notes)


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