I'd almost forgotten what bass sounds like and feels like. Electronic music sound especially good. I think it's a massive improvement on the onboard sound from a Raspberry Pi 4. I can't do an A/B test easily because you have to disable the onboard audio which isn't difficult once you know what to do but it isn't easy to find out what to do if you're not a real nerd. Like the other review says there are zero instruction for this product. I'm still using (and want to continue using) Raspberry Pi OS. If anyone wants to know, this is what you need to do (maybe there are other ways but this worked for me) Open the terminal (the black box on the taskbar) and type sudo nano /boot/config.txt press "enter" then using the arrow keys find the line "#dtparam=i2s=on" and delete the #. Next find and delete the line "dtparam=audio=on" and replace with dtoverlay=hifiberry-dac Then find the line dtoverlay=vc4-kms-v3d and add ,noaudio (note the comma - no spaces). Finally press control and x (together) then "y" for yes to save the changes then reboot.
I have no complaints about the service from Audiophoniics. I picked it up from the post office a couple of days after ordering. I chose this DAC because it was the cheapest that has RCA outs and mini-jack for headphones. The RCAs aren't disabled when you plug headphones in (which suits me). The best slightly less than 40€ including shipping I've spent for a long time.