The Fosi Audio PH04 distributes a single stereo source to four independent headphone outputs, each with dedicated volume control and high-power amplification. This configuration accommodates simultaneous monitoring for studio tracking, live sound applications, fitness sessions, or shared listening environments without signal degradation. The all-3.5mm design eliminates adapter requirements while ensuring reliable connections across standard consumer headphones. Four isolated amplifier sections maintain clean stereo imaging and dynamic range regardless of load impedance variations. The ultra-compact metal chassis prioritizes portability without sacrificing build quality, making it equally suitable for mobile studios, broadcast facilities, or personal use. An integrated power switch enables convenient operation while minimizing standby consumption. Supplied with a 12V DC power adapter and backed by an 18-month warranty, the PH04 serves as an essential tool for audio professionals and enthusiasts requiring multi-user headphone distribution with independent gain control