W A R N I N G !

W A R N I N G !

This page is full of non-facts and bullsh!t, (just like the internet and especially forums and other blogs), please do not believe entirely without exercising your intellect. Any resemblance to real things in reality is purely coincidental. You are free to interpret/misinterpret the content however you like, most likely for entertainment, but in no case is the text written on this blog the absolute truth. The blog owner and Blogger are not responsible for any misunderstanding of ASCII characters as facts. *cough* As I was saying, you are free to interpret however you like. *cough*

Wednesday, December 17, 2008

Random quote of the day... plus when people don't have specific knowledge

"A switched-mode power supply (SMPS) is the most convenient but susceptible to high-frequency switching noise and distortion. Linear power supplies use a more sophisticated rectification process during AC-to-DC conversion"

This guy obviously never looked at schematics before.

Well, first thing, I always thought there is always only one type of rectification process commonly found in consumer PSUs. (Or is there even another?) Diodes, in full-bridge or half-bridge, or perhaps vacuum tube, which is a form of diode when used in this way. Rectification is converting AC to DC anyway, nothing to do with regulating, or fixing the DC output voltage.

Switched-mode and linear power supplies differ in their voltage regulation method. I won't go into details... but google for PWM and it's easy to understand.

And, since when is the small, efficient SMPS less sophisticated than the big, bulky, inefficient, hot, linear-regulated power supply? It's possible to build a linear power supply from scratch, try that with a SMPS. Nobody use SMPS with audio stuff anyway due to the switching noise issue mentioned above, but the good part of SMPS is that you can build a PSU that supplies 500W and weighs less than just the transformer of a linear PSU that supplies 50. But I digress.

This quote is found on the website of a "respectable reviewer". No serious audio person find that reviewer serious anyway, so I'm not here to find faults with it. The not so serious people who believe whatever this website says, well, they belong to an entirely different market group (like iPod vs iRiver), and we need this kind of people to keep the industry making big buc... I mean barely sustain.

Add: I'm amazed that the second page of the review actually has a part titled "Why SLA (sealed lead-acid) battery". His (the reviewer's) experience with a UPS has somewhat left him ho-hum about SLA batteries in general. Even market leaders like APC and Belkin, their SLA batteries last about 3 years at best, under 2 years on average.

He didn't ask why even the market leaders use SLA batteries in their UPSes. He should have.

And so after some research, he found that, under the strengths of SLA:

(5) ability to maintain potential voltage under load
(amazingly he put it under the 5th point out of 6)

Duh! That's the reason why they're still being used today. In more commonly-heard phrases, it is "able to supply large amounts of current" due to "low internal resistence". I mean, it can start your car. Try starting a car with NiMH batteries. If they don't explode before that.

He also forgot about the weaknesses that it's fucking huge and heavy and hence inconvenient, low energy density (low amount of stored charge for its size), kill themselves over time (as the electrolyte evaporate), liquid corrosive and gas toxic plus causes acid rain, environmently unfriendly. Then why are we still using this piece-o'-crap which is like the first rechargable battery invented in 1859? Reason above. And a strong enough one - to date, no other battery type can come close to the 100A that they can produce. You can get 100A by connecting lots of batteries in parallel, but that would be too expensive and too hot.

And he stilled asked another company representative to confirm that SLA is the best choice for this application.

Maybe his brain has been damaged by music. Or maybe his ears are thinking for him. "Trust your ears", it is.

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