Used with Hifiman Sundaras and worked well. Used roughly two years, the. went the lazy route and have Apple AirPod Max headphones now. Also used this to switch to external Vanatoo T0s via optical. Works well, no issues. - USB & Analog Playback and Record multi media audio system. - Built-in high-performace headphone amplifier (32 - 600 Ohm headphone impedance recommended), delivers clearer high, deeper bass and richer sound. - One optical digital input for most HDTVs, a game console, or other digital audio sources with optical digital output, and feed a high-quality audio signal into your stereo system. - Type B USB jack feeds digital audio from your computer into the HP-DAC1 onboard digital-to-analog converter, bypassing your computer's sound card to yield much clearer sound with stored music files and Internet radio. - A pair of RCA outputs lets you connect the HP-DAC1 to your home audio system's receiver, integrated amp, or a set of powered speakers for a high-end, compact desktop stereo. - The volume control can adjust the output level for both Headphone and RCA Output (Once the headphone connection is used, there is no signal on the RCA output, the signal will simple mute analogue outputs when headphone jack is inserted) - S/PDIF output supports (for USB Input source only) digital surround multichannel formats such as AC3 / DTS pass-thought. - TI PCM1754 24-Bit 192-kHz DAC & PCM1808 24-Bit 96-kHz ADC chips for low-noise, high-fidelity stereo definition sound. - *******Currently only supports IOS 12 version software or below for the iPhone/iPad device********* Spec: - Frequency Response: 20Hz ~ 20kHz (+/-0.5 dB) - SN ratio: -95dB (A-wtd) / Line Output - Max Line Output Level : 4.2 Vrms (THD <1%) - Line Output Impedance: 100 Ohms - Total Harmonic Distortion: Line Input <0.01% / Digital Input <0.05% - Headphone Output Level: 0.1% THD 1KHz 32mW (32 ohm) - Power Supply AC Adaptor: DC 15V / 0.4A / 6W