Features: Experience unparalleled sound with the auditory PM-1 HiFi Headphone Amplifiers for rich auditory experience across all your devices. Suitable for mounted Piezo Pickup Preamplifier; This machine is a JFET high impedance charge type amplifiers circuit, which is not affectedly by the length of the input line and not with frictions effect; The battery is rechargeable and can last for 10 hours on a single charge. Perfect for desktop setups, portable use, or professional studio environment this amplifiers enhances yourexperience with powerful output and compatibles 6.35mm Specifications: Charging: TYPE C DC5V Input oroutput ：6.35mm 1/4TS Gaining: When the capacitance value of the Piezo Pickup is 10nf, it is about 20db,The lower frequency limit is 30Hz Input impedance：greater than 10M Ω Output impedance: 600Ω Length, width and height:about 65mmx63mmx24mm/2.56x2.48x0.94in Component：Metal and Plastic Package Includes: 1Set Piezo Pickup Preamplifiers note: Due to problem of lighting effect there might be tolerances in product, please understand. Please allow 0-2mm error due to manual measurement.