XM6: No other portable amp offers all this:
The XM6 is the most feature-packed portable headphone amplifier on the market today. Strong, clean, unsurpassed sound quality is made possible by the XM6's two-chip ultra-low-distortion FET amplification stage, mated to a separate two-chip output buffering stage, all in a monoblock configuration. All chips use gold-plated sockets, which allow for easy upgrading/rolling to configure the sound to exactly your taste. This attention to detail adds up to audio performance with an SNR well in excess of 100dB, and near-zero distortion (We are one of the few manufacturers who actually publish quantitative audio test results of our amplifiers. Test results here).
The XM6's USB-DAC stage is equipped with Texas Instruments' SRC4192 digital upconverter, feeding the legendary Wolfson Micro WM874x-series DAC (your choice of WM8740, WM8741, or WM8742), operating with 24-bit resolution at a 192kHz sampling rate. The result is absolutely unrivalled USB audio quality.
The XM6's features leave other amps far behind: there are controls for bass, treble, and gain boosts, and a control to enable/disable 75Ω output impedance (for those of you with lower-impedance headphones and IEMs). The XM6 also has Practical Devices' patent-is-pending Active Variable CrossFeed, which is simply not available on any other brand of amplifier. There is also a rear panel LineOut aux connector, and a first for any portable USB DAC: a multimedia controller joystick. And finally, the XM6 has intelligent microprocessor control, a 1-hour no-fuss Lithium-Ion FastCharge® battery system, auto power-off, and a low-battery indicator.
Lastly, the XM6 simply looks and feels spectacular. Available in your choice of color, the XM6 has robust, all-aluminum construction. It just looks, sounds, and feels spectacular. And all backed by an industry-leading 3-year warranty and no-hassles 30-day money-back satisfaction guarantee.