I just received mine, this thing is tiny in comparison to other dongles, app is slooooow and clunky but it was expected I had to restart the app disconnect and connect the dongle for the custom EQ to work, there is a 5 band fixed graphic EQ , gain control and a parametric EQ with 5 bands, you have the option for Low-Shelf, High-Shelf and Peak filters with a frequency response from 20-20kHz a gain form -12dB to +12dB and Q from 0.25 to 8.00, frequency response can be adjusted in 1Hz increments, filter gain in 0.1dB, Q in 0.01 and general gain in 0.5dB. There is an import function and you can save custom presets (I dont know how many yet, still experimenting) or download from the web, there are just a few and the descriptions are in Chinese.
It is supposed to have a more granular volume control (up to 60 steps) but I can get it to work, with the app on or in the background volume control on the cable mic/control is unresponsive and the hardware buttons work with the usual android 15 steps also the multi-function button does not work within the app on so no no next or previous song.
I figure I load the EQ I want and disable the app until needed again.
****BUT all of this is meaningless because of a huge channel imbalance (low level plus no highs on the left channel) on Android* (which was the intended use), on the PC it works as supposed to but with the EQ on it reduces the volume considerably, it might be the gain implementation (I'll experiment later).
*Tried with different phones, tablets, IEMs, cables, music players, streaming and YT. Even uninstalled the app, with and without EQ and tried with another phone without the app, same thing.
I'll wait for a few weeks/months to see if it's corrected with a firmware update if not off to the drawer.
EDIT. I experimented a bit with the general gain and if I increase the gain to the maximum the volume is as it should I didn't detect any distortion but just in case I lowered the intended pre-amp from the maximum gain.