Review on Portable Headphone Amp With 3.5Mm Stereo Audio Out, GAIN Support & Lithium Battery - Compatible With IPhone/Cellular Phone/MP3/MP4 /Computers. by Brett Martinez

The amplifier does its job fine. I am not an expert in sound evaluation but at least I could hear minimum degrade of sound when connected with high quality earbuds. Few things to mention, it doesn't include any 3.5mm cable so if you just have earbuds you might need male to male 3.5mm audio cable. It included nice long usb charging cable though. Secondly, I actually bought this hoping that it may be able to amplify signal from my shotgun microphone and I confirm this didn't work out. But it still does its job as a headphone amplifier and had the best available price so it's 5 star product.