Nobsound NS-08E Vacuum Tube Integrated Amplifier Mini Audio HiFi Stereo Headphone Amp This is Douk Audio's own brand, Nobsound. Nobsound features a low price coupled with high performance in a small, simple package delivering high fidelity, specially designed to provide the audiophile with the performance they deserve. Now, NS-08E upgrades for the first time in the past three years. New version uses upgraded 6J3 tubes. Sound is warmer and softer with more brilliant treble, more powerful bass and quieter background. This unit can easily power high-performance headphones including the HD580, HD600, HD650, K701, K702, Q701, and many more. 24~600 headphones would be recommended while armature earphones are not suitable. New version can also be used as tube preamp for other amplifiers or active speakers. For better preamp performance, we recommend NS-10P (ASIN: B07719G56B). Input and output audio jacks are both 3.5 mm. Please note, package does not include audio cables. New version uses ceramics tube sockets, which have better oxidation resistance and can be more durable even after long-time use. Tubes can be replaced by 6J3, 6J4, 6J5, 6K4, 6K5 and many more. You can see our description for the full list of replacement tubes.