FIIO E12 DIY Headphone Amplifier [SILVER Limited Edition] w/ 7 High Fidelity, Ultra-low Distortion OP-Amps and Buffers E12DIY can attain 750mW@32, 150mW@300 (using OPXXX+BUFXXX combo), satisfying the power requirements of most headphones on the market Simply use the supplied hex key to unscrew the back cover and pull out the case to access the E12DIY main board. Note: Please turn off the unit and disconnect the USB power connection before opening the unit. Since the nature of the product, this item cannot be covered under manufacturer's warranty, once you open the amplifier unit and switch with amplifier components. E12DIY comes with 7 high fidelity, ultra-low distortion op-amps and buffers: Including four op-amps: AD8620, AD797, OPA1611, OPA604and three buffers: BUF634, LMH6321, LME49600for a total of 12 different stock sonic configurations. Users can also use the supplied adapter PCBs to install other op-amps and buffers for infinite variations in sound. Please double-check for correct orientation of op-amps and adapter PCBs before installing the op-amps and the PCBs onto the main board and re-check after installation. Installation with reversed orientation may destroy op-amps and the E12DIY.