For its price, it is a good tool. I have the BeyerDynamic DT 770 Pro (80 Ohms) headphones and the Focusrite Scarlett 2i2 (2nd gen) interface.
The Focusrite barely covered me on its own, I just didn't want to have the switch at 90-95% (it was barely audible and had a hiss from the console).
Now with the amplifier, the volume on the console is at ~75% and the volume on the Behringer is also 75%.
It could work at lower levels, but in Windows I always have the volume at -10db (on a digital mixer). Generally, I prefer to lower the volume a bit in applications. I want to have headroom and I prefer to change it digitally, so I can save the levels exactly each time. In analog hardware, the levels are not visible or I usually don't remember them.
Noise starts to be heard at around 80% volume on the Behringer.
In short, it does its job.
Positives:
- Affordable.
- Four different and independent headphone channels.
- There is no sound transfer from one channel to another among the 4 ports it has.
- Generally clean signal up to ~80% volume.

Negatives:
- Build quality. The knobs are wobbly, not stable. But expected for its price. After a power outage and being connected to a surge protector, one of the four ports (which was active at that time) started producing an electric buzzing noise. I disconnected and reconnected it and did various tests. Now it appears "randomly" while turning the switch and also disappears randomly. When the switch stops turning, the noise stops as well. So it works, but I am concerned about the future (especially if the power goes out again). The other devices on the same surge protector (including the PC, Focusrite, DBX 286s, speakers) did not suffer any damage.

For 30 euros this little thing does magic, I personally had the Focusrite Scarlett 2i2 3rd Gen which supports up to 200 ohm headphones, and I got 250 ohm headphones (BeyerDynamic DT 880 Pro) so it already gave satisfactory volume but I wanted more for mixing, I also got a small balanced cable (6.3mm - 6.3mm) just enough to go from the sound card to the headphone amp, and of course now I can plug in up to 4 headphones instead of 1 and the volume is MORE than enough regardless of the fact that it says it’s for 80 Ohm, and the reason is obvious, both the sound card and the headphone amp logically provide power.

Positives
- Very cheap
- Very practical
- Gives you the volume you want
- Supports up to 4 headphones

Negatives
- Although the materials for the amp are good, the cable looks very cheap for the power, but it does its job
- No 6.3 balanced cable is included to connect it to a sound card (but you only pay 30 euros, don’t expect everything)

Very honest and correct, the sound quality does not have any obvious distortion and is quite satisfactory even for me who wants it for mixing and music production, at high volumes there will be some distortion, I recommend not turning the knobs all the way up, neither from the sound card nor from the amplifier to avoid any distortion, and be careful not to work for extended periods at high volumes because your ears will hurt and you’ll lose frequencies before you become grandpas.

23/5/2026 Update
Nothing has happened to it, TOUGH! and I have it plugged in all the time. Only once did it make some weird noises but I also had power issues during that period and I just unplugged the power and plugged it back in. And after the restart it worked just fine again... I still see it’s cheap and honest!!!!

The existing reviews are very detailed, and I will only add a few things from the perspective of a beginner, as it was purchased for simple, household use. It is a stereo headphone amplifier AND splitter, meaning you can connect up to 4 headphones/devices, controlling the final volume for each separately.

Both features work flawlessly, as I did not notice any bleeding in the splitting and the final amplification is very satisfactory, especially considering the low cost of purchase. The same applies to the build quality of the device and the power supply.

Finally, in response to my own question in the thread, YES, it can amplify the final volume of sound to some extent even in speakers (multimedia and cheap HiFi systems), with the appropriate connections, adding a bit of "volume," even if it is not intended for this purpose.

Note that all the ports of the device are 1/4 (6.35 mm), so you will need the corresponding adapters/converters if you want to connect cables or headphones with the classic 3.5 mm jack.

I bought it in order to enhance the signal from my computer's DAC to the DT 990 PRO (250 Ohm).
At first, I tried the headphones directly on the DAC because the motherboard has high-quality audio components (Z390 Aorus Master), but I immediately realized that it wasn't enough for 250 Ohm and they needed amplification. Since I was financially tight at that time and couldn't afford to spend 100-300 euros on a powerful amplifier, I decided to get something cheap to do the job and see how it goes...
Searching here and there on the Internet, I ended up with this splitter-amp because I saw on YouTube that despite claiming to have an 80 Ohm output, it can provide enough volume for 250 Ohm headphones.
So, with 25 euros, I feel completely justified in my choice, as it can deafen you at 100%...
In terms of quality, it's perfect up to 75-80% of the dial, but beyond that, it becomes so loud that it causes slight distortions in the sound.
For anyone who really wants a cheap amplifier for professional headphones, I highly recommend it!
If one considers what the guy says in the review below (and it's true for professional-grade equipment), that with 25 euros you can't even get a cable, then you understand that we're talking about a VFM (Value for Money) king in its category.