The OEQ2 has a switch that lets the user select between Balanced Line inputs and RCA inputs. A circuit that incorporates differential amplification will only amplify the difference between two conductors or wires. In car audio, most components are connected together with RCA patch cables. Under ideal circumstances, the difference between the hot center conductor and the outer shield is the musical signal. Cars are anything but ideal, however.
Electrical noise is generated by the alternator, fan motors, windshield wipers, brake lights, etc.
These noises can be inductively coupled into the RCA patch cables. When this occurs, the noise spikes appear on both the center conductor and its outer shield. Since differential amplification only amplifies the difference between the two conductors, the noise spikes are NOT amplified, and they are consequently eliminated from the system. In addition, the OEQ2 features independent left and right input sensitivity controls as well as calibrated bargraph level indicators. These indicators are extremely useful when setting system levels.