LA90 is an amplifier using TI's LM3886 Class AB IC chip. This IC is used one each for left and right cH.
This chip is used in various Chinese amplifiers.
The LA90's power adapter is the high frequency switching power supply you are talking about.
Let me guess, LM3886 with a small signal opamp for error correction in its feedback loop a-la what
@tomchr made with
modulus-286
Here is the
thread on DiyAudio
Or same thing but with Howland current pump topology a-la My_ref, late Mr.Penasa already published in early 2000s
Diyers had this level of performance for 2 decades now, was wondering when someone would actually notice you can top charts at ASR for almost "free"..
Actually totally agree with poster above and his sentiment, pure wonder nobody thought to copy this before, it was litterally on the table the entire time..
I wouldnt be surprised if this LA90 had more power with a higher voltage brick, i built a My_ref and you can arbitrarily limit when it poops out if i just lower or raise the voltage (to a degree).
LM3886 is actually a bit harder to find these days so the only reason i can see a manufacturer mass producing with this part at this day is if they stumbled upon these designs.
Also not sure i get all these 50W is nothing people, thousands are building for example Nelson Pass's amps which rarely go above 10W (and the crowd who likes to waste 300W of power for 10W out doesn't exactly listen to bookshelves), and i dont think i've ever listened to music louder than about 3W (granted its nearfield and SPL drops off by inverse square law).
But come on, 20W already should be illegal to have if you live in an apartment, and 50W surely enough for all but the largest of rooms.
There are genuinely people who might need the power but im willing to bet 90% of these people never put a voltmeter in AC mode to the binding posts of their speakers while playing as loud as they ever listen, and
calculating the actual (roughly) power with their speaker's nominal impedance.
This is like when you get used to seeing 1000HP supras on youtube and now scoff at everything in the three digit range