Prior to designing my own power supplies, I did a market research and was surprised to find strikingly cheap offerings on the Chinese market. In this article, I share my ideas regarding those offerings and compare such designs to my own designs.
During my research, I was surprised to find super cheap rectifier and capacitor assemblies on the market. The complete modules cost way less than parts alone from reputable distributors. Here is one example featuring eight times 10000µF capacitors, proper rectifiers, small heat sinks for the rectifiers, screw terminals, probably bleeder resistors and even LEDs:
All this comes at a price tag of roughly 40 USD to 50 USD, even including free shipping. What could possibly go wrong? From a design point of view, I can even tell from the placement of the components that they can't have done anything wrong here. The PCB seems to feature two layers - pretty state of the art. The rectifier diodes seem to read "ST" and in case those are not counterfeit parts, they should do their job nearly forever. The tiny heat sinks should be able to dissipate energy loss under realistic operating conditions. The only thing I can imagine being sub par, are the big capacitors. Most modules I've seen so far use capacitors of some unknown brand. Maybe they will explode some day, maybe not. Since I have replaced hundreds of exploded electrolytic capacitors on PC main boards in the past, I'd say unknown brand capacitors might have a tendency to explode likely sooner than later. Some modules are offered with capacitors from well-known manufacturers and this more than doubles the price of the modules. It is a matter of trust to buy alleged quality parts from counterfeit country. So for everybody who doesn't mind maybe replacing capacitors or the whole module one day, those cheap modules from China are an excellent choice. They come in many different sizes and none of what I've seen so far look bad. What I miss is all the tiny components that make the difference between basic functionality and a well-engineered product. This could be a point for DIY. Known good quality of components is the mayor point of DIY. By the way: The Hitachi HCG capacitors shown on above assembly are fake. Reference: DIY Audio and ESP for example. Probably most parts used in those Chinese modules are fake.
Here is the cost breakdown of my large power supply for the modular high end audio amplifier system:
|Part||Quantity||Cost p.p. [€]||Cost total [€]|
|Cage clamp terminals||36||0.25||9.00|
|168€ incl. VAT|
The calculation clearly shows that the DIY module built using quality parts, costs two to three times as much as the Chinese modules made of fake components. In case the rectifiers are mounted to the chassis, 20€ could be saved without compromising performance. A stripped down DIY module could be roughly 10€ cheaper.
While it seems tempting to buy one of the cheap Chinese modules, the risk of receiving assemblies that possibly are made of counterfeit components is too high in my opinion and I don't want to risk building a bomb instead of an amplifier.