1.Unique volume control?: When the DAC Headphone Preamp is connected to the speaker and the earphone at the same time, the earphone takes priority. After the earphone is unplugged, it automatically switches to the speaker. The volume button can adjust the RCA output. (The volume button of the decoder on the market can only control the earphone, can not control the RCA. ) 2.A variety of input and output modes?: Headphone Amplifier can be PC-USB, optical fiber, coaxial three inputs, can be connected to TV set-top box, DVD, DCD; output mode has RAC, 6.35mm headphone port 2, can be connected to power amplifier, tube vacuum amp, active speaker. 3.Chipset: The mini headphone amplifier chip uses CM6642+CS8416+CS4398+TOP6120A2+NE5532P+OPA2134PA to provide strong guarantee for tone input and output. 4.Efficient protection and long life?: The headphone audio amp uses OPA2134 and NE5532P two special op amps specially designed for audio. The op amp can be freely replaced and upgraded. At the same time, two relay protectors may protect the headphones and speakers. 5.Perfect for Music and Gaming?:When you use it for music, it can bring you fantastic music enjoyment.DAC-K3 also is really good for FPS gaming.Can use it with dolby atmos and the directional sounds perfectly."