OP+BUF Audiophile 4.4mm Balanced Headphone Amp 18-600 Ω HiFi High Current with 4.4mm Headset Jack/XLR Input and Classic OP+BUF Architecture, Mini Desktop (U01)

The circuitry is purely DC amplification, delivering exceptional sound quality (with 4 independent channels). The pure analog amplification circuit and control system are designed to faithfully reproduce the authentic analog sound of music. The soundstage, positioning, and airiness of the details are superb!