Lysignal 6J1 Tube Box Headphone Amplifier Preamp DC12V Black The pre-amp does little on amplification, but it's main purpose is to act as a "buffer" so that you have good frequency response that covers the bandwidth usually from 20 to 20KHz. Your power amp should be responsible for the amplification. 2pcs 6J1 tubes with optimal integrated circuit will make you get powerful, dynamic and sweet TUBE SOUND! Tubes can be replaced, 6AK5,6BC5, EF40, EF95, CV8505654; Much fun and high playability. Unique DC12V1A power input with power adapter. Universal and safe in voltage. Parallel RCA stereo input/output. Standard RCA cable correction. Please note RCA cable is not include. Suitable for digital amplifier,analog analog and active Speaker. Not suitable for turntable phono.