Equal loudness control circuit

MOS Power IC Full Range

Photocoupler

As shown in Figure 1-87, this is an improved equal loudness volume control circuit. This design utilizes a single common potentiometer, making it both cost-effective and efficient. The circuit’s simplicity is its strength; it employs only a minimal number of components yet delivers impressive results. The operating principle of the circuit is straightforward: when the internal impedance of the signal source is significantly lower than that of resistor Rc, and the load impedance is large while being driven by resistor Rp (which itself must be much higher than resistors R1 and R2), the capacitor C only affects the high and mid-range frequencies. For low-frequency sounds, the capacitor essentially opens up, ensuring that the bass remains unobstructed. This circuit provides a superior listening experience by balancing the perceived loudness across different frequency ranges, which is particularly useful in audio applications where maintaining consistent sound quality is crucial. Its compact design and effective functionality make it an excellent choice for those looking to enhance their audio systems without overcomplicating the setup.