HF Player Unlock Application allows you to enjoy Hi-Res Audio by enabling a digital connection to USB audio-compatible external devices (such as a DAC) via OTG (On The Go) cables.* Please confirm the functionality of the digital connection between HF Player and your external device before purchase. If an error occurs during license authentication, please reinstall HF Player and the Unlock Application.- CAUTION -Onkyo USB Audio HF Driver is not supported on DAC/headphone amplifier devices without volume circuitry*. Use of unsupported devices may risk damage to playback equipment or hearing if volume is set to maximum when connected digitally. Purchase of the Unlock Key App is not advised when connecting unsupported devices to HF Player. Furthermore, pPlease ensure that Onkyo USB Audio HF Driver is set to OFF in the HF Player app. Note that this setting disables Hi-Res Audio capability.* Products include CREATIVE Sound Blaster E3, Resonessence Labs HERUS, Deff Sound DDA-LA20RC, Audio-Technica AT-HA30-USB, etc.- HF Player (Free Version) Features -- Touch-adjustable linear-phase FIR equalizer offering 16,384 discrete bands of HD equalization- Create, name, and save your own custom EQ presets- Select an equalizer preset optimized by musicians for Onkyo headphones- Playback of Hi-Res Audio files including FLAC / DSD / 192 kHz/24-bit WAV at no additional charge- USB Host Audio Function (up to 48 kHz with the free version)Note: Audio with a sampling rate exceeding 88.2 kHz output via the headphone connection, AOS connection, digital connections via OTG cable (free version only) is downsampled to 44.1 kHz.- Unlocked Functionality -Support for Hi-Res Audio output via Onkyo USB HF DriverEnable lossless and Hi-Res Audio output to external devices such as USB DACUpsampling FunctionWhen connected to Hi-Res Audio-compatible USB DAC, audio files are played with up to 192 kHz/24-bit upsampling and bit extension.