For audiophiles who prefer sound quality over ergonomics, the CL441DSP comes with a master volume control, a simple rotary knob that is small enough to be installed in many easy-to-reach places. The use of the master volume control allows the CleanSweep to provide maximum signal-to-noise ratio and eliminates any effects that a volume-dependent equalization curve would have.
The thoughtful product development team also incorporated an auxiliary input on the CleanSweep to allow your iPod (or other audio source) to easily play through the system via line-level input, rather than poor-sounding FM modulators. Left and right input level potentiometers with clipping indicators allow the volume of the auxiliary source to be matched to the volume of the factory source unit. The CleanSweep controls the volume of the aux input and switches between the factory source unit and the auxiliary source through the master volume control, so it must be installed when incorporating an external audio source. A provided source indicator LED can be mounted and glows green with the factory source and red with the auxiliary source.
Many of today's OEM source units are data-bus controlled and do not have dedicated wires that signal when the unit is on or off. The CL441DSP features audio input signal-sensing circuitry to control the remote turn-on wire for the aftermarket amplifiers (and other products). One detail of the signal sensing on the CleanSweep that I like is that the unit turns off immediately when the ignition is switched off, while other units stay active for the duration of their turn-off delay, even after you've removed the keys and gotten out of the car, making me wonder if the unit is going to power down or not. Another nice detail is that the signal sense circuitry has an on/off switch that allows it to be turned off in the rare case that the OEM system features its own remote turn-on wire or if the user wants to have a switch to manually activate the CleanSweep.
The CL441DSP is designed to correct the response in systems that have four full-frequency outputs. Some vehicles only have one pair of full-range outputs available (with the others electronically crossed over by the factory amplifier), which may result in losing the ability to use the factory fader when adding a CleanSweep. In many vehicles, the frequency-divided signals can be summed back into a full-frequency signal with the use of a line output converter with summing capabilities. Complex multi-channel audio systems like the Mark Levinson systems in the newer Lexus models and the surround sound systems in the Acuras and Volvos are not prime candidates for the CleanSweep due to their multi-channel, divided-frequency outputs.
As with any aftermarket car audio product, the CleanSweep cannot single-handedly rid the world of bad-sounding stock systems, but it will likely be considered a "superhero" by installers who have been struggling to get great sound into these "evil" integrated source units. I applaud JL Audio for creating a product that is well engineered and smartly addresses a major problem facing the world of aftermarket car audio. I'm sure that this is the tip of the iceberg and they are already working on the next several generations of CleanSweep products. With the CL441DSP, JL Audio has definitely set a high standard for other OEM audio integration products to come.