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Class D Switching Power Amplifiers and Power D/A conversion

Beomaster refit - controversial?
Beomaster refit - controversial?
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Old 12th September 2019, 10:04 AM   #11
TroelsM is offline TroelsM  Denmark
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Quote:
Originally Posted by Turbowatch2 View Post
Since I tried some very cheap Alibaba / eBay SMPS boards, Im cured of using these old laptop junk. You never know how it does with audio.
You get these in any voltage and they are remarkable silent.

Example:
DuoWeiSi 36V 250W 7A Switching Power Supply Board Audio Power Supply AC DC Isolated Power Module 220 to 36V-in 3D Printer Parts & Accessories from Computer & Office on Aliexpress.com | Alibaba Group

AC-DC 100V-265V Bis 36V 5A Schaltnetzteil Adapter Switching Power Supply SMPS K1 | eBay
The ebay ones may "sound" better, but as for safety and EMC I would trust and old laptop-adapter much, much more.

Not saying that the ones you show are dangerous, just saying that its very hard to tell without proper (destructive) testing or analysis.

Kind regards TroelsM
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Old 12th September 2019, 10:14 AM   #12
tallnutt is offline tallnutt  Australia
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Thanks! I will try the 24V.
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Old 12th September 2019, 10:25 AM   #13
tallnutt is offline tallnutt  Australia
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What about these? Just as bad?
DC 5V-24V Universal Regulated Switching Power Supply 1A-60A 10W-480W LED 3D PSU | eBay
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Old 12th September 2019, 10:41 AM   #14
TroelsM is offline TroelsM  Denmark
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Quote:
Originally Posted by tallnutt View Post
Sorry, but I dont know. As I see it, it comes down to trust. Do you trust HP, Lenovo and their QA-dept. more than a ebay-seller?

Again: maybe the ebay-PSU's are perfectly fine, but how would you know?

I bought many parts from ebay, but never anything that connects to mains power.

TroelsM
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Old 13th September 2019, 03:05 AM   #15
Turbowatch2 is offline Turbowatch2  Germany
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Hi TroelsM, have you ever read the fine print on your holy brand brick?
HP or Lenovo buy their SMPSs from some Chinese Manufacturer for less than a $ and put a label on it. These bricks sure meet the demands of a Laptop. Some work well with a D-amp, others not.
These cheap power modules linked here,from Ali or ebay, are produced in the millions. The design is proven, probably stolen from the US and works very well with D-amps. They have a lot more power than the usual laptop brick which ends at 90 watt.
The world has choosen to use medium-tech equipment from the yellow man for reasons of cost.
Sure some Danish high ender can ignore the fakt and be sentimental with brand names, but many here want the most for their money and look for proven low cost alternatives. Like the rest of the world. When the big manufacturers buy in China, why should I buy expensive? Just to waste money and in the end get the same China stuff, relabeled?
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Old 13th September 2019, 03:16 AM   #16
Turbowatch2 is offline Turbowatch2  Germany
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@tallnutt
these you linked will work just the same. They are more refined, as you can adjust output with most of them, maybe +-5%. The metal case makes them safer to touch and keeps the EMI inside.
As the D-amp always radiates some kind of high frequency dirt, it should be put in a screening container (case) anyhow. So the finished amp will be protected from touching and radio emission. The naked modules are much smaller, so some will prefer them.
If you experiment a lot and use your DIYS amps open for quite some time, to test (no kids and animals!), you might be happier with such a SMPS in a case. DIYS is "decide it your self".
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Old 13th September 2019, 04:19 AM   #17
tallnutt is offline tallnutt  Australia
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It's the B&O unit as a whole that is more likely to make magic smoke than any of those PSUs at the moment, which is why I'm now gutting it ��
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Old 14th September 2019, 08:28 AM   #18
TroelsM is offline TroelsM  Denmark
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Quote:
Originally Posted by Turbowatch2 View Post
Sure some Danish high ender can ignore the fakt and be sentimental with brand names, but many here want the most for their money and look for proven low cost alternatives.
Are you refering to me?. Yes I'm sentimental about the B&O stuff, but by no means high-end.

I would prefer the low cost alternative anyday. If you look at my old posts youll see that I have done an active speaker with and old laptop-brick-psu. I used an ebay boost-regulator to get the voltage from 19V to 34V to fit the ebay classD. ( Btw: the boost-regulator was unstable and had to be modifed to work.)
El-cheapo active LOUDspeaker
High end...

Yes, most likely the mains-powered PSU's from ebay are perfectly fine, but you dont know.... - if Lenovo, Dell or HP made a PSU that were dangerous I think we would have heard about it.

Please note that I have expressed nothing about sound-quality or whether one PSU would work better than the other. I only talked about safety.

Its up to the individual DIY'er and please do as you like. - but mains voltage can and will kill you if you are having a bad day.

Kind regards TroelsM

Edit: My old trusted kitchen-radio for the last 15 years have been a Beomaster 3000. Works perfect and I love it, but if the amp failed beyond repair, I would consider classD from ebay.
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Last edited by TroelsM; 14th September 2019 at 08:32 AM.
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Old 14th September 2019, 09:37 AM   #19
Turbowatch2 is offline Turbowatch2  Germany
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Did you ever try touching the mains line with your hand, while standing in a ditch on a concrete floor, with wet shoes? You learn the hard way that mains voltage is not good for your health and may be your last experience ever. Did this in a garage where the landlord had done the electricity by him self and accidentally exchanged the black and green/yellow wires in a connector. So earth was alive... which is what the Amazonas should be, but not the case of a lamp.

I honestly hope that anyone here has a degree in electric engineering, but that might not be the case with some. The EU is trying all it can do to prohibit building or repairing anyone from anything. Even today, practically you are not allowed to DIYS any electric device, car or any installation in a building. Even a single chassis passive loudspeaker has to be EMI tested, if you give it to your daughter or best friend.
I love posts where people are concerned about safety. In a few years we will be only allowed to buy Chinese appliances, with our hands tied behind our backs. Then, everything will be safe. Brave new world.
So the Beomaster has to be carefully taken to the recycling facility, not refited, you are right. That would be much more safe and create new work space in China.
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Old 14th September 2019, 10:45 AM   #20
Guerilla is offline Guerilla  Denmark
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Lets move on to subjekt ☺
Cheers!
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