Review on Douk Audio U3 Mini Class A Headphone Amplifier - HiFi Desktop Home Stereo Amp (DC5V) by Alma West

=Update=I hooked this unit up to a 12v power supply today and it has worked with my 600 ohm AKGs are given the best volume and range. but I also realize that I might have made a mistake when I originally tested them, thinking that the RCA outputs on my DAC/ADC are just plain line outputs. but they are actually controlled by the DAC's master volume. So yes. i was just an idiot It has enough power = Original = Well, that was a bit disappointing. I bought this because the headphone output on my DAC (Scarlett 2i4) wasn't powerful enough to drive my 600 ohm AKG studio headphones. about as gluttonous as it gets. Unfortunately, after hooking up this headphone amp, I found that its output (via 6V USB power supply) was no better than that of my DAC. At full volume, I'm certainly at enough volume to hear what I'm doing, but not enough to get full, rich bass and detailed sound, and I'm not at enough volume to work with headphones in a noisy environment. So I'll have to see if a 12V power supply with more amps gives me better results. Otherwise I'll have to send it back.