Apple dock can improve sound quality

If you want to match the output level of your iPhone/iPad device with amplifier you can use one of the docks provided by Apple. In practise, the dock with the line output level should improve a sound quality when it is connected into the line level input of the amplifier.

Line level signals are the highest level signals before amplification. This is the type of signal that typically flows through your audio system before the amplifier connected to your speakers. The two types of line levels are consumer and professional. The consumer line level is rated around -10dBV and that is what you’ll find in products like a CD player.

One example of the docks that support line live output is A1505: iPhone 5s Dock. You can use also the iOS compatible docks from other manufacturers.