The only problem, and it's important to me, is that when it turns on and when it connects, it speaks at full volume. You either have to turn off the speakers or unplug the cables when you turn it on, otherwise it will deafen you or wake up the neighborhood. I don't understand why the Chinese insist on putting voice prompts on Bluetooth devices. A simple beep would be enough. Other than that, it does its job very well. Very good amplification, good sound, but there is lag. Next time I will prefer something else like Logitech or TP-Link.

For the money I spent (5€), I believe it is the best in its price category. One disadvantage it has is that when someone receives a call on the connected mobile, it makes a very annoying sound that could damage the speakers if the amplifier is of poor quality or if the volume is simply at maximum

Completely unexpectedly better than I expected. I bought it for €3.99 in an offer I found for a last piece. Get it. It works excellently. I have it connected to a Yamaha rx-v2700 amplifier with a Bose Acoustimass 10 iii system and its performance is sonically incredible without distortion, with a slight hiss close to 8/10 of the volume—and we're talking about 7.1 with 140 WRMS per channel. Tested even with the cheap 3.5 to two RCA cables from the package. But I should say that I use it with a good Huawei adapter. What else could anyone expect at a price up to €10? .....I would even give it 6 stars.
01/10/2025 update.
It works excellently. The only thing I want to add is that in my case, when it is turned on or off, there is no voice prompt—it's a pattern found in many Chinese Bluetooth devices—but only a guitar tone, which is not at all annoying.
It probably varies from batch to batch.

I didn't expect it to have such a nice sound and such a great range, I haven't figured out how the NFC works or if it works at all but I don't really care that much

Very good value for money, an important advantage is that both outputs (jack and RCA) play simultaneously without latency between them. A significant disadvantage is that when you turn it on, you hear a voice at FULL VOLUME informing you that it has turned on and is in BT mode, in case you miss the flashing red and blue LED that resembles a police patrol car beacon. This is the reason why I will change it, no matter how insignificant it may seem. If you make the mistake of turning it on and off or if the power is cut while your speakers are at maximum volume, you will understand

Easy pairing and connection.
The connection within range is stable.
However, the sound quality is not suitable for Hi-Fi listening.
For 5 euros, it is a decent purchase.