The Fosi Audio SK01 combines headphone amplification and analog preamplification in a single portable device, delivering 2400mW RMS at 32 ohms across impedances spanning 16 to 300 ohms. Three-band tone control—treble, midrange, and bass—with center-detent positioning enables precise acoustic customization, while the PURE button defeats all EQ for transparent signal path operation. Dual 3.5mm connectors accommodate line-level inputs and outputs, with additional 3.5mm and 6.35mm headphone jacks providing universal compatibility across consumer and professional headphones. The isolated power architecture eliminates ground-loop interference, ensuring clean signal reproduction during extended listening sessions. An integrated high-capacity battery delivers up to six hours of continuous operation, establishing the SK01 as an ideal companion for desktop audio work or portable use. The precision-engineered aluminum alloy chassis reflects meticulous craftsmanship while maintaining a compact footprint. Whether functioning as a dedicated headphone amplifier, customizable preamp, or parametric equalizer, the SK01 adapts to diverse audio applications with exceptional versatility and sonic performance.