6J1 HiFi stereo tube valve Preamp Preamplifier amplifier warm up the sound Mini kit,size:L100*W70*H50(mm),it's cool. packet 3 x 6J1 valve, one is for backup PCB Circuit layout is reasonable and beautiful, minimize noise,warm sound,perfact for listen person singing. ,Best for your desk headphone amplifier or home power amplifier.make the sound more warm. About the input and output interface.all using GOLD RCA interface. included transformer,110V,