Strange product. Initially, I tried it at work, on a 2011 Mac Pro, and the sound was really bad when the volume went above halfway. To be more specific, the sound came out of Sony MDR-ZX310 headphones and it was a complete disappointment. Distorted and muddy. The reason I bought it, of course, was that the headphone jack on my iMac at home came loose from its position. So, trying it at home, I connected it to a TP-LINK UH700 USB hub. Then I plugged a splitter into the headphone output and connected my speakers (Logitech Z333). I want the splitter so that I don't have to open the speakers every time I need to use headphones and, of course, to avoid constantly plugging and unplugging from the back. Like magic, the sound was crystal clear. And in both cases, the system sound was always at maximum. But on the iMac, it was/is really good and clear. Maybe it lacks a bit in bass, but I can't say that for sure yet. That's about the speakers. Now, if I connect the headphones directly to the splitter, I do have clear sound, but without much bass. Things are a bit different if I connect the headphones to the port that has the volume knob. There, the sound improves significantly, but if no music is playing, there is white noise. The speakers, however, don't have white noise. It's a bit confusing to explain the chaotic difference in sound between the two computers. The older Mac Pro definitely has lower volume compared to newer Macs in general. But that's as far as it goes. I see it like this: it's a cheap product, partly bought out of necessity, and it will serve me until I fix the audio output on the computer, but this inconsistent performance between systems concerns me. Once I fix the port, I will try it on Windows 7 and 10 as well. I have no opinion on the microphone.

Update 26.12.2019: After an upgrade to the operating system (from El Capitan to High Sierra), if the computer goes into sleep mode for a certain period of time, then I have no sound and I can't play any videos or music. I have to close the Hub and reopen it in order to have sound again. Tragic. I also notice that if I slightly adjust the cable, the sound cuts off. This card remains consistently in the hub, without constant plugging and unplugging.