PreSonus HP2-15 Personal Headphone Amplifier Battery-powered Stereo Headphone Amp with TRS Inputs, 9V Battery or DC Power Supply, and Belt Clip - Musical Garage SCH
Ray Samuels Audio SR-71B Fully-Balanced Portable Headphone Amp (Playback 60) - The Absolute Sound
Best headphone amplifiers 2023: boost your personal listening | What Hi-Fi?