Yes, I would like to hear your impressions of the little amp. Glad you got a power supply.
People love it, but USB power has its limitations. I have a couple of meters that show the power wave form… it is excessively noisy on every supply I have checked. No big deal for charging flashlights or phones, but not what you want for an audio amp.
Douk Audio U3 PRO quick test results:
I really like it.
I watched part of a movie where I had serious problems (with my old headphone amp.)
The new headphone amp worked perfectly with the problematic part.
The audio was not distorted, and the overall volume could be cranked up to about 175% or 200% as loud (as the old amp) without any distortion, though I don’t usually listen to media at such a high volume.
Yes, with everything in my audio chain close to maxed out, there was no distortion, and it was more than loud enough for me.
If the Douk Audio U3 PRO works like this for a few years, I’ll be quite happy.
So, as people say, time will tell. 
Glad you found something that does what you want it to do.
I slightly changed my previous post.
When I have everything maxed out, there is distortion, though I don’t know if that’s because of the amp or not.
Having said that, I can have everything close to maxed out without distortion.
So, if I hear distortion, I just need to turn something down a bit. 
Be careful, your eardrums might become the weakest link in the chain.
There can be more than one thing causing distortion… I think most common is the headphones or in ear monitors breaking up from too much drive level. Then over driving the input. Better to turn down the source a bit and raise the gain on the pre amp/amp. The audio output stage of many laptops or PC are often not the best. Driven too hard they can cause all kind of nastiness. The last is the amplified distorting. If the specs on that little amp are accurate at 1.5 watts, it really should drive many headphones/IEM cleanly to levels that are so loud that they will damage your ears before you will get noticeable distortion from the amp.
The question is are you listening at your normal level when you hear distortions, or are you just exploring the limits of what it can do? I mean how often would you listen with everything maxed out?
One other thing, some movie tracks have been shown to exceed 0 DB.. which causes digital clipping, heard as distortion. There is not anything you can do about that.
Bottom line is that there are quite a few places where nastiness can creep in. It may not be the amp at all…
More important, just turn it down. Long term exposure to high sound pressure levels will damage your ears. After a certain point, it can happen very quickly. Distortion can add transients well above the average sound level… which just makes things much worse. Once you damage those hair cells, it is permanent hearing loss…
Ask me how I know.
BTW, what headphones or earphones are you using?
I have had good results with PEACE equalizer and its “prevent clipping” option. Not sure what OS you guys use, but it works pretty well with windows. I believe the dev’s name is Peter Verbeek. You might have to spend some time dialing the channels per application (per game, per music genre, per headphones) but once you have it dialed in it’s great. It MIGHT be considered cheating in games because it can boost the sounds of footsteps, but it’s not really that different from not hearing the footsteps because of crappy OS or default equalizers causing a handicap instead.
I have software that will do this, as in prevent clipping in the audio stream that goes through them. But it can’t help poorly mastered source material. That was what I was referring to in this case. So if it is there in the source, you have a hard time fixing it in playback. I suppose you could “remaster” the movie…
If you had the original untouched soundtrack.
“Claude, remaster this movie for me and tune the audio similar to xyz reference”
Claude: returns a long-winded fart noise “Is this what you were looking for?”
Sounds very interesting. But I wonder if it can fix something where the source that you start with is just hosed. If there is lost digital information where they just push past 0 DB I think that original data is just gone… dropped bits, unrecoverable, and it sounds horrible. This doesn’t happen frequently, and should never happen with a good sound engineer, but it is documented on some movies Such as the intro of Ready Player One. The only way to fix that would be by using the original digital recordings… or tapes, that are, hopefully, recorded properly.
I haven’t messed with Claude, I should check it out . I am still concerned about privacy and the fact that the “free” levels for most of the AI is quite limited.
Take the Muff Fuzz out of the signal chain, and it should sound a lot cleaner. 
i was joking about Claude lol, I do my best not to use higher functioning AI, even most of my phone’s AI are disabled or hamstrung somehow. The telemetry is a different story, but that’s besides the point…
I imagine that a good data forensicist could look for similar compressions/algorithms, and slowly reconstruct/reproduce a sound close enough to the original sans the aberrations…kind of like the ship of theseus paradox. If you can recreate the complete set of individual conditions that comprised the original piece, you might be able to replicate the original piece faithfully. The only issues then would be “is it worth the resources” and “if so who will provide for the costs”?
uses tweezers and floss to clean out my mouth ahem, what?
I use Avantree Audition Pro headphones.
They’re my headphones of choice, and I have six pairs that currently work.
They’ve been discontinued, so I’ve been getting them used off of eBay.
…
I don’t normally listen to loud media–I was testing my audio chain.
Even with everything close to maxed out, it wasn’t loud enough to damage my hearing.
It was just louder than what I usually listen to, and I didn’t listen at that volume for long. 
By the way, I’m 49 years old.
I had my hearing tested somewhat recently, and I have excellent hearing for someone my age.
I know when I am being exposed to media (or noise) that is potentially loud enough to damage my hearing, and I go out of my way to avoid those situations. 
I’m not obtuse enough to intentionally damage my hearing–no offense to anyone else. 
EDIT:
I’m glad that people are concerned about my hearing, but in this case, it’s unnecessary. 
negative decibel hearing crew unite!
I am glad that you are careful… for your well being, of course, not mine.
But the only true way to know is to measure. I have found that I can easily confuse myself with sound levels. As our perception of loudness adjusts with exposure. It is like our brains just turn down the perceived level over time.
I was watching a movie not long ago and thought it was pretty loud, but still OK. Especially an hour or so in. I decided to take out my Sound level meter (SPL)and check. Much to my surprise the average was over 100 DB with peaks up to 110 DB. Much too loud for long term exposure.
I am sure you know how to take care of your ears. I am just pointing out something that really surprised me.
I figured the following out a couple of days ago, but I didn’t get around to posting it until now.
I underestimated my new amp.
It can get louder than I first reported.
It can get so loud that it’s too loud for me, and if I maxed out everything in my audio chain, I’m sure it would damage my hearing.
I had forgotten that my Bluetooth headphones also have a volume control, and they were turned down quite a bit when I said the new amp was “about 175% or 200% as loud (as the old amp)”
I don’t know exactly how much louder my new amp is, but it’s more than loud enough for me.
To find out, I’d have to hook up the old amp and compare the two, and I don’t feel like doing that.
By the way, this is my old amp, and it claims to increase the volume by a maximum of 25 decibels.
https://www.amazon.com/dp/B0F9WR5K97
What they mean is that they boost bass by bumping 50 Hz frequency range by 25dB. Not sure why anyone would want to do such a thing. Sounds shady.
As far as power, it mentions 160mW@16Ω to 80mW@600Ω, but it does not mention any distortion levels, so not very useful.
Anyway, your new amp seems like a significant improvement.