I recently tried a few of the cheap Fosi and Aiyima Class D amps to replace my old B&K ST-140 as a bi-amped bass amp for my woofers below 65hz with an active crossover. Not exactly the answers you’re looking, but I can summarize my experience.
The first attempt was an older Fosi TDA7498E chip that came with a 24V power supply. At a glance it was rated for 160W x 2. Into an 8 ohm woofer with the stock power supply and no passive crossover components, it lost control very quickly and flapped the woofers at surprisingly low volumes. I packed it up and returned it.
Next up was an Aiyima A07 Premium with a stock 32V power supply and more modern TPA3255 chip rated for 300W x 2. This unit did a lot better, but still didn’t hit with the same impact as the B&K (which is not known as a bass monster). Bass notes sounded like a tenor trying sing in the baritone range....it just didn’t have the same extension and weight. I later added the 48V power supply and upgraded the opamps from NE5532 to MuseS02...better, but still no joy.
I decided to try the Aiyima A07 Max bridged in mono, which from a glance claims 600W, and came with a 36V power supply as stock. I gave it the MuseS02 opamps and the bigger 48V supply....bass performance was better yet than the A07 Premium, but still not making the grade vs what I’ve come to expect. With the biggest PSU and better opamps this amp should have been putting out somewhere near 100 realistic watts per channel, same as my B&K, but they sure sounded boomier, less dynamic, and less authoritative. I did not get any exposure to midrange and treble on my main system with any of these, so can’t comment on it.
I even ran the A07 Premium with the 36V supply from on one channel, and the A07 Max in mono with the 48V on the other channel, which is about as much power as I could squeeze from these units. Still just not quite right. Within seconds of hooking the B&K back up, there was no doubt...it sounded better....not really even close. At that point I stuck a fork in the experiment and abandoned the idea of using the cheaper versions of these Class D amps.
I kept the A07 Premium with the 48V GaN supply as a bench amp and back up, but I suspect that the stated power ratings were published by the marketing department. I’m actually a little shocked that in this day and age that it’s still legal to make claims that are closer to wishful thinking than reality. My experience tells me that these could replace a typical mid-fi AVR, and I wouldn’t hesitate get one for my daughter...it even sounded ok on my bench driving either Energy CB5 or KEF C30s, but these were not accomplishing what I had hoped on the main system even when optimized with the biggest power supply . They get a big "meh" from me at this price point...perhaps better examples at higher price points will fare better.
