To cheap to possibly be good? ali and ebay audo modules. (class-d)

[Lambda]

I'm sure many of you have seen this sort of products:

Small and super cheap amplifier modules.
There are countless variant's and i have lost track. are there some known to avoid and some knowen good ones?

Most of them use singe IC all integrated designs and don't differ a lot from the datasheets reference implantation, so how bad can they be?

Back in the days (~15 years) ago before Bluetooth speakers where a thing and Class-D brand new i have build a view mobile sound systems with the
Tripath ta2024 T-Amp boards.
I was pleasantly surprised by the quality and most impotently for this application the energy efficacy.

https://store.sure-electronics.com/ /wondom seem to make good Quality products?

Are there any tests and measurements for some of this ultra cheap stuff around?

 

[somebodyelse]

I guess it depends what you mean by good - even datasheet performance for those amp chips isn't great, and at those prices the output filter inductors probably aren't great. Some of those haven't been following the datasheet advice about psu cap positioning either. For the money you probably can't complain too much though. Probably comparable to the LP-2020A which is the cheapest tested so far but not the worst. Remember to factor in the cost of the PSU before deciding.

 

[Bob-23]

I've built two of those famous Gaincards, based on LM1875 (with slight modifications*) - and was very positively surprised. They're good!

And they include a switch-on muting and dc-protection circuit with Omron-Relays. Price: 17,40 Euro for an amp, of course, transformer (symmetrical) excluded. And get big heatsinks, can't be big enough, the chips are getting really hot.

The muting circuit is based on UPC1237.

It's a kit, easy to solder (get the orientation of the chip right).

WARNING: Never switch on the amp without heatsinks installed, even for a test run,

* Mod.: metal-film resistors in amp circuit instead of carbon, Wima input film caps (3,3uf) instead of bipolar caps, reduction of the 47uf cap to 22uf (muting sequence was too long), adding fly-back diodes & resistors to relays

https://www.amazon.de/TOOGOO-Verst？Rker-Platine-Gaincard-Verzerrung-schwarz/dp/B07XYBJ8TP/ref=sr_1_1?__mk_de_DE=ÅMÅŽÕÑ&dchild=1&keywords=TOOGOO+lm1875&qid=1614551236&sr=8-1

(Remember - as you seem to be German/EU: Beginnning with July, 1th, we are going to pay 19 % import taxes, and DHL is adding 'processing frees'. The date of arrival of your order counts. But that'll still be cheap, for what the amp delivers).

Look on Rod Elliotts 'ESP' for the general description of the astounding capabiltiies of these 'opamp'-power-amps (projects 72 & 19). There's also the LM3886, which is a bit stronger. To me, the LM1875 is powerful enough.
https://sound-au.com/

EDIT: I reduced gain from 29 to 22 (10k resistors instead of the 7,5 k resistors)