[Saris]

I've used those before, they have a horrifying amount of noise on the output, lots of RF noise, and a very audible high-pitch whine. They also overheat very quickly even at half the 'rated' load.

[JohnFen]

Well, maybe don't go with a buck converter that is quite that cheap.

[Saris]

It can be surprisingly hard to find much in between the super cheap stuff and the really expensive stuff! Those cheap ones work in a pinch though.