Built-in high-performance headphone amplifier (20 ohm to 300 ohm. Supported sample rates include USB: up to 96kHz, and optical digital: up to 192kHz at 24-bit depth. Volume is controlled directly from the D1 front panel via the digitally-controlled analog potentiometer. Audioengine D1 DAC/ Headphone Amp (Playback 54) The Audioengine D1 uses an AKM AK4396 24-bit/192kHz digital-to-analog converter. The D1 is powered directly from the USB bus and power is passed through two stages of regulation to ensure no USB bus power variations affect the audio quality. The high-performance headphone output was designed for a wide range of headphones and will satisfy even the most demanding headphone enthusiasts. high-performance DAC (digital-to-analog converter) for detailed, low-noise stereo sound built-in high-performance headphone amplifier (20 ohm to 300 ohm. of headphones and supports headphones with impedance as low as 20 ohms. The D1 includes a headphone amp based on the TI OPA2134 low noise opamp. Audioengine D1 24-bit DAC - digital-to-analog converter allows you to bypass. The D1 can process digital audio at any bit depth up to 24-bits and any sample rate up to 192kHz. Due to the high signal-to-noise specs of the AK4396 and the added benefit of double redundancy power source conversion and filtering, the D1 presents impressive low noise and low distortion characteristics. The D1 uses the AK4396 DAC, which is well-regarded for its low noise and high fidelity. Relative Humidity: 5% to 95% non-condensing Operating Temperature: 32 to 95 degrees F