The HP-A4BL High-Resolution DAC / Balanced Headphone Amplifier from Fostex is a high resolution digital-to-audio converter and balanced headphone amplifier well suited for professional audio engineers, mastering engineers, and audiophiles. The HP-A4BL supports PCM audio up to 24-bit/192 kHz and DSD audio up to 11.2 MHz. The front-panel offers a balanced 4-pin XLR headphone output, an unbalanced 1/4" stereo headphone output, while the rear-panel offers stereo RCA outputs, optical S/PDIF I/O, and a USB 2.0 connector. The HP-A4BL has 2 gain staging levels, allowing you to boost the output of the amp by 10 dB without needing to touch the volume knob. The selectable filter allows you to cut-off lower frequencies if desired. The HP-A4BL ships with a power supply, USB cable, and 4 rubber feet.