I’ve been going down the audiophile wormhole this year and no trip there is complete without an overpowered headphone amp. Since my favorite headphones are very sensitive and don’t necessarily need an amplifier, getting this unit was a low priority. 

The price difference between this U3 “Pro” version and the “Mini” version was so small that I opted for this one. The Pro includes a 3.5mm headphone jack as well as a 3.5mm input jack on the back plate. It also has a slightly larger amp which is listed by the company at 1500mW at 32Ω. 

I was happy to see mine arrived with a power cord that has a built in wall transformer plug. I assumed it came with a power cord sans the wall plug. 

The U3 Pro sounds great. From what I can tell, it doesn’t seem to color or add harmonic distortion to my audio chain. I’m a practicalist and didn’t want to spend more than I needed to add a bit of clean power to my signal. In reality, it can add a lot of juice to my signal if I dial it up. 

Now I can run my mp3 player at about 75% volume and I’ve never gone above the 12 o’clock position (50%) on the volume knob of the amp. In practice, that means I don’t have to run my mp3 player any louder than 75% and it therefore stays distortion-free. I’ve also noticed my battery life on the player lasts longer since it’s doing less work amplifying the output signal. The volume knob on the U3 Pro doesn’t crackle or pop when adjusted, and volume ramps up evenly as expected. 

The volume knob has an etched line (indicator) for the levels which can be hard to see in low-light. So I plan to paint that red for visibility.