Sorry if my post topic is misleading but recently I found this tube hybrid amplifier called "Sherwood DT-555". It is a Chinese built amplifier with a 6N3 tube. I tried it with all my ear phones and they had too much background noise, I think it is because all of them are low impedance sets. It runs fine with a pair of 6 ohms Onkyo bookshelf speakers and changing tubes changes the sound as well as when you knock the tubes it can be heard from speakers. Does anyone know anything about these amps? I searched the internet and I couldn't find any information. Also I must mention that it is heavy for it's size. Guy who I bought it from has no idea what it is or where it came from.