Review on Nobsound Headphone Amplifier Earphone Pre Amp by Dianne Williams

I just listened to these few tracks with Sennheiser HD 650 headphones. My source is a 320kb MP3 file from an LG G7 phone with the DAC built in and enabled. I have a hard time describing the tube sound other than giving silky smooth high frequency response, removing harshness and adding dimension to the high frequencies. The bass also has a nice "fullness" feel. Using it as a headphone amp increases my headphone listening enjoyment. The unit itself seems solidly made, I cranked the volume all the way up, no music, I didn't hear any extra hiss, I didn't hear any distortion. I also have a Monoprice Liquid Spark and a Fiio A3 portable amp and it seems to work just as well as those amps although it lacks the portability of the Fiio. The HD 650 are high impedance headphones and they pretty much require a headphone amp to work well. This inexpensive amp seems like a great solution. I didn't twist the tube and am enjoying the performance of the included tube, although I appreciate the opportunity to try others.