M-Audio Bass Traveler - headphone amplifier

Bass Traveler is a portable headphone amplifier with two headphone jacks that lets two people listen at the same time to the same signal. Many personal digital music players have a limited output for driving high-quality headphones - which may have a higher impedance, a lower passband voltage sensitivity or both - but Bass Traveler has a 2-level gain switch to boost the signal level, so the sound is always crisp and clear.