Douk Audio U3 迷你 A 类耳机放大器 HiFi 桌面立体声放大器，适用于 HD650/K701/DT880/T70/RS1e

This headphone amplifier is great if you run it on 16-18 volts DC. I also put a LM4562 opamp in place of the 5532.

Not sure if the value proposition is that great Honestly. It is about $30. $14 or so for a good power supply.

The unit I got had a problem with audible electrical hissing, and this happened frequently.

The channels were also mismatched on the unit I received.

Stepped volume knob is always a bad idea. Also why notmake the part that the user is interfacing with more premium feeling.

The sides and top of the unit are nicer in look and feeling that the only actual part the user touches.

The knob felt cheap and scratchy.

Make the knob smoother, and not stepped.

Also make it feel more premium and nice.

Fix QC issues as my unit had 2 major issues.

JDS labs atom amp+ is only $50 more than this once you consider the power supply. It is a much much better amp.

Consider the value proposition here in a landscape where the atom amp+ exists.

Analog inputs only. However the sound from my receiver and portable CD player is excellent. Purchased to drive my high impedance 250 ohm, headphones . Head phone outputs on many HiFi receivers, computers or phone DACs will not drive high impedance headphones properly. While they may be loud enough, the detail, depth, and bottom, isn't there. This head amp fixes the problem but needs at least a 2.4 or more power supply. I'm using 5v 3amps which does the job. The USB power plug connector needs to be twice as long as the one included.

First, this thing DOES NOT COME WITH A POWER SUPPLY, at least not a serviceable one. The first page of their instructions tell you that you need to buy a separate power supply, which more than doubles the price of this item. Save yourself the time and money and buy a better amp that comes with a real power supply—it will end up being cheaper than this, and much much better quality. This thing is cheap trash.

Has great fidelity and even better gain. However after 6 weeks of Sunday Morning ONLY use at church, the headphone jack has become intermittent. Seems the Chinese do not know how to properly make a 1/4 inch phone jack. I have seen this happen in other China made audio gear. Too bad, I was hoping for more utility out of this product.