It's my first post here in the forum, but I would also like to write something about the Aiyima D03. Please forgive me if the English is not translated correctly.
I like the TPA3255 chip very much and also own a somewhat modified amp in this design.
Because you hear so much great things about the Merus MA12070 chip, I also had a S.M.S.L DA09, which sounds super detailed, but I find it only suitable for the near field. Further away, about 4 meters I missed stage. Also, he could not convince me in the low frequency. With the tone controls, it was also never balanced enough for me. Let's put it this way, it always sounded "digital" to me and never like a good Class AB or Class A amplifier. No question, it is good. But not my taste.
Currently I own 4 self-built speakers that are tuned very linear. No matter which speaker I connect to the D03, it always sounds balanced and at no time "digital". Not the super detail-loving resolver, but also miles away from undercutting anything. Sound setting on neutral almost always fits but also the tone controls are super implemented.
At the beginning I connected it to a 24V/5A switching power supply. That was already OK, but with the Meanwell LRS-350-36 adjusted via potentiometer to 33V it became even better.
The connectivity is also great. Only Android devices via USB he does not find. My cell phone connects with BT APTX HD.
Conclusion: Very good sound at a very fair price. Measured values do not matter to me. My ears say keep it and will be very happy with it for a long time.
I hope I could help some interested