We tested LineOut Pro with three different car stereos and two in-home speaker systems, and the sonic differences were virtually imperceptible between the audio coming out of an iPhone 4 or 4S’s headphone port through an 3.5mm auxiliary cable and what came out of the LineOut Pro via the Dock Connector, when the iPhones were set at peak headphone volume output levels. Depending on the device you’re using—some iPods, iPhones, and iPads…
