darry wrote on 2025-05-14, 21:55:
I would not trust the ripple and noise characteristics without having tested/measured them under load.
They could be crappy designs, very optimistically specced, using counterfeit/relabeled/factory reject regulator ICs, etc.
I agree, and that's probably the case with majority of any pre-built modules out there from the China malls. Still, not all of them are over-rated / over-specced. In some cases, it's just a matter of how the info in the description is presented - i.e. I've seen a few of these modules rated for 20 Amps, but if you looked more careful into the description, that was really only peak current, and the real (constant) output was more along the lines of 10-15 Amps. Also, another thing is that no matter which module one gets, if it has electrolytic caps, they will probably need to be replaced right from the start with higher quality ones. The usually cheapo caps used on these things should not be expected to last. In the case of one amplifier module I have, the 35V-rated caps are probably re-labeled, because they get awfully leaky when going over 30V. So my guess is they are 25V caps cheaply re-labeled as 35V caps. Apart from that and having to up-spec the output filter polypropylene caps a little, the module does work as expected and delivers the rated output power without distortion or getting hot.
I also have a bunch of cheap Blutooth to analog audio adapters, and these work exactly as advertised. So not all stuff out of the China malls are bad / over-specced. 😀
The one thing I would NOT suggest for anyone to buy from there though, are high-power BJTs - all of them are going to be dodgy counterfeits with very questionable ratings. Case in point: I bought 10x E13009 transistors for PSU repairs... and I knew by the low(ish) price that they will be dodgy. I expected them to perform a rating or so lower - i.e. around that of E13007 BJTs. But they didn't. Not even close. 🤣 More like under-rated E13003's with heatsinks or over-rated E13005's. Just terrible. I can still use them... but for much lower power rated applications.
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So yes, you do bring a very valid point here. It will probably take for someone to play around with a few of these regulator modules to determine if there is one (or more) that stands out among the others for this kind of use / application. Other than that, I figured I'd mention these modules, as it still might be an easier option for people with less electronics knowledge to attempt a mod like this, because at least they don't have to deal with building an entire board from scratch.
Ozzuneoj wrote on 2025-05-14, 16:06:
Man, why didn't I think of this? Yeah, I'd love to know if these are viable and if 3A is enough.
https://www.aliexpress.us/item/3256806057827680.html
Less than $7 US for 10x 5v-30v to 3.3v converters on 18x13mm boards sounds great. The location of the contacts isn't really ideal though.
Yeah, that another thing with pre-built solutions: the contact / solder points to install on the board may not be in the most optimal place, unlike a custom design, where you can put things exactly where you want so you have less wires / mess.
As for weather 3A would be enough... I'd say pick something with twice the current rating, just to be safe, for the reasons darry mentioned above.
From what I've looked at, the price difference isn't that big between the lower and the higher rated current models.
