Unlike primitive line-output converters that only reduce the level of factory audio signals, the CleanSweep® CL441dsp employs a powerful DSP (Digital Signal Processor) to automatically analyze the frequency response of a full-range factory audio signal and then applies 30 bands of powerful equalization to each channel. This counteracts any factory equalization and provides a clean, flat signal for your aftermarket amplifiers and speaker systems to sound their best. You can use your factory volume control(s) or the included Master Volume control when listening to the factory source unit.