The ZHA-4 splits a single stereo headphone output into four separate powered 1/8 headphone jacks, each with their own volume and mute control. Perfect for bands, podcasts, productions, and more. Two AA batteries provide hours of portable power. For longer sessions, connect the USB-C port to a portable battery or plug directly into the wall.What’s Included: ZHA-4 Handy Headphone Amplifier AA Batteries (x2) Stereo Mini Audio Cable (19 / 50cm) Quick GuideSpecifications:GAIN: 24 dBCLIPPING LEVEL: +18 dBuOUTPUT IMPEDANCE: 47 FREQUENCY CHARACTERISTICS: 10 50 kHz, +/-1.0 dBDYNAMIC RANGE: 100 dBINPUT IMPEDANCE: 10 kPOWER SUPPLY: 2*AA batteries (alkaline, nickel-metal hydride or lithium) / External USB Type-C DC5V / 1 AWEIGHT: 180 gEXTERNAL DIMENSIONS: 130 70 52 mmESTIMATED CONTINUOUS OPERATION TIME USING BATTERIES: about 3.5 hours with Alkaline / about 4.5 hours with NiMH (1900 mAh) / about 8.5 hours with Lithium-Connecting 4 headphones with 32 load-Continuous battery operation times were determined using in-house testing methods. They will vary greatly according to use conditions.