I have used headphone amps before…and they do work well bu integrated is a whole other step in the right direction…. VAMP Integrated Headphone Amp, DAC and Battery Pack for iPhone 4/4S Spy-worthy gadget for the modern audio connoisseur ushers in a new era of pure sound, sophistication and power. VAMP features a 150mW x 2 amplifier, dedicated pure Digital-Analog-Convertor, VQ audio enhancements, optical audio output and backup battery all integrated into a solid metal case that transforms an ordinary iPhone 4/4S into a sophisticated and stylish high fidelity device. Powerful Amplifier A 150mW x 2 amplifier bypasses the iPhone's internal amp designed for smaller, low-impedenance ear buds and provides optimal power to drive even the most demanding and high-impedance headphones*. VAMP's rotary volume knob allows you to finely adjust the volume and its hi/lo gain switch adjusts the output level to match the power required for both low and high-impedance headphones. *High-impedance headphones and professional / studio headphones require or benefit significantly from a headphone amplifier Pure Dedicated Digital to Analog Convertor VAMP's dedicated DAC extracts the iPhone's digital output and converts it into its analog form for the purest and unparalleled audio listening experience. VQ Audio Enhancement VAMP […]