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Old 3rd October 2013, 10:18 AM   #11
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by Bernie7 View Post
Really, is there any trace on a mobo that can take 10A, let alone 50A?
Yep, there will be planes, multiple layers... I designed a motor drive that delivered 50A at 48V and was no big deal. This is common practice now.

Quote:
Originally Posted by Bernie7 View Post
Even if there are switchers inside, I could still argue that one switcher less (their mother supply) can help in audio.
There's no even to it. There are multiple switchers in a laptop. It's common for the core voltage to be delivered by a switcher using six phases or more. Then there's the 1.8V logic, 3.3V logic, and maybe some 5V logic, all from switchers. In a laptop switching is the only choice. It's now becoming common for a class D amp to drive the speakers.

My opinion is that a well designed switcher is not audible. Even with a bad one in the chain, replacing the brick will not benefit.
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Old 3rd October 2013, 12:33 PM   #12
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What about just using a brick but adding a LC filter to the output. In this case
wouldn't .1mh and 5uf just about kill any high frequency garbage from the brick powersupply?
 
Old 3rd October 2013, 07:02 PM   #13
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by woody View Post
What about just using a brick but adding a LC filter to the output. In this case
wouldn't .1mh and 5uf just about kill any high frequency garbage from the brick powersupply?
There's probably something similar already in the brick, especially if it's the OEM brick. But, that still doesn't negate any noise the might be present from all those internal switchers.
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Old 11th October 2013, 06:19 AM   #14
Bernie7 is offline Bernie7  Singapore
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If a better psu does nothing for the laptop, wouldn't it at least reduce injected switching noise into the ac supply powering the hifi?
 
Old 11th October 2013, 11:05 AM   #15
DUG is offline DUG  Canada
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How about putting something like a battery in between the brick and the laptop's switchers?

Oh wait, there is one there already.

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Old 11th October 2013, 12:09 PM   #16
Bernie7 is offline Bernie7  Singapore
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Quote:
Originally Posted by DUG View Post
How about putting something like a battery in between the brick and the laptop's switchers?
Umm....how would that help, the brick could be polluting the ac supply, or couldn't that happen?
 
Old 11th October 2013, 10:20 PM   #17
DUG is offline DUG  Canada
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Quote:
Originally Posted by Bernie7 View Post
Umm....how would that help, the brick could be polluting the ac supply, or couldn't that happen?
The battery would help isolate the noise of the brick from the supplies in the laptop.

There are regulation that limit the amount of EMI pollution that switching supplies can produce...both conducted and radiated emissions.
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Old 11th October 2013, 10:52 PM   #18
FoMoCo is offline FoMoCo  United States
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Quote:
Originally Posted by Bernie7 View Post
If a better psu does nothing for the laptop, wouldn't it at least reduce injected switching noise into the ac supply powering the hifi?
If it's the power supply that come with the laptop, it's not likely you'll notice any difference. If it's a cheapy from epay, you might. Those are also fire hazards though...
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Old 21st October 2013, 07:24 AM   #19
Cristi is offline Cristi  Europe
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This post evolved so much since I wasn't able to access the forum that most of the important things were already said. I would add the following only:

1. The idea of using a linear power supply to supply the notebook is useless. would be much larger and heavier than the notebook itself, with poor efficiency, at best 50% and the amount of heat to be dissipated will create reliability issues. The idea of replacing the internal switches with linear switches is even more hilarious, is almost impossible and if someone would really try to do it, a lot of problems will arrise, most probably will never work. Let's see why. Like someone already said, core voltages down to under 1V at currents up to 100A or more are currently common nowdays. How could someone imagine a linear regulated power supply able to provide let's say 800mV at 120A ? I know, there are laboratory power supplies used for chemical or physical experiments, or in industry very low voltages and huge currents are still used for spot welding, electrolysis, hard chromium plating and countless applications. but their power supplies are huge, expensive and power hungry. Next. suppose that we passed all these obstacles. we have all the necessary voltages ready: 800mV @ 120A for core, 1.8V, 2.5v, 3.3V 5V at few hundreds of mA up to few A and 12V at 1-2A for display backlight. How we bring these voltages on the mainboard while the voltage drop and regulation is good enough to keep it constant? remote sensing of voltages ? that might work for keeping the voltage steady under constant load but during fast current demand changes ? the system will be very unstable, at half meter wire carrying 120A at 800mV..... Anyway, suppose that these obstacles are passed, inside every computer, desktop or notebook are dedicated power management IC's which are connected through dedicated buses to a controller and all voltage and current settings, feedback, monitoring and protections status are transmitted in real time. we have to replicate this too.
So, I don't think that will anyone ever try to do this kind of power supply with the current available computers down to the point-of-load converter.

2. Most of the original adapters which come with notebooks are properly designed and built, so the EMI and safety are no reasons to concern. the fact that the power supply is not within computer itself, sometimes sit 1m away from computer, it minimize radiated emission susceptibility to a point that has zero effect to a computer which itself containst at least a dozen of switches on board. Conducted emissions are still fairly low for these adapaters, and changing them with some "audiophile" special treated alloy (money waster) is useless.

3. Things are changing when we talk about after-market adapters, or even adapters which come with brand new no-name-no-brand computers made by my surrounding neighbours. I got scared when i opened the first adapter, and I keep getting scared when I open each new adapater. If couple of years ago their safety was poor, then bad, now is terrible to none. I attach some pictures of a transformer from a notebook adapter bought as a travel spare from my computer. it eventually ended up chopped, and bought another one which cost me about 12 times more and even if I was 99.99% was original I wanted to see with my own eyes what is inside before I dare to use it, although it voids it's warranty.
What we see in the picture, there is no trully isolation barrier tape between primary and secondary and the primary and secondary wires are touching eachother. The only reason why this transformer hasn't killed anyone yet is because the wire insulation still exist. but imagine what happens after 1-2-3 years of thermal cycling, 20-80-20-80.....20-80*C and so on.
This is how most of the brick laptop adapters transformers sold for a burger on fleabey looks like inside. I advise all of you to open one and check. Although the plastic case is ultrasound welded (even screws or glue are expensive nowadays) is easy to open, put it on a hard surface on its side and hit the opposite side gently with a hammer on the line where both covers join. You might also be surprised if you'll find inside next to the tiny, half empty pcb board, one or two special components, connected to nothing, long and thin, wrapped into scotch tape and made of cement, or in best case iron scrap. it's only purpose is to convince the uninitiated buyer that the product is genuine, since it weights the same as the original one. If you're power supply is really deent made, you didn't lost anything by opening the case, (whell the power supply might not work if the opening process is not done properly) but at most you know the risk grade before putting your life in danger. Internet is full of discussions related to this issues, too bad that i can't access most of the pages with relevant content. I wonder why....
One reason why most of the SMPS which I desing and produce are using LLC topology is that beside efficiency and low noise this topology allows highest isolation to be achieved between primary and secondary, safety being a priority especially for DIY. with a split bobin transformer where clearance/creapage is at least 5mm and is visible, not hidden under layers of tape where moisture, impurities, and all sort of conductive elements can create a disastrous bridge.

4. A high quality SMPS for notebook computers should only be considered if it can be demonstrated that this would improve the sound performances. Use a battery or better 3x6V batteries to supply computer externally and see if something changes. eventually, use it's own battery, every laptop has one, right ? if there are no significant changes, and I'm almost sure about, that is a waste.
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Last edited by Cristi; 21st October 2013 at 07:31 AM. Reason: wrong count :-(
 
Old 21st October 2013, 07:29 AM   #20
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