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Old 24th March 2010, 03:54 PM   #1
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Unhappy Need SMPS circuit for LM3886 based audio amp

Thanks in advance.

I need a suitable smps for my LM3886(x2) based audio amplifier. I'm new to smps I can't find any smps circuit that suits. please anybody help..
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Old 25th March 2010, 03:45 PM   #2
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anybody please suggest is that possible to use smps for lm3886 based amp
if yes please give me a schematic , link or any idea..
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Old 25th March 2010, 06:15 PM   #3
luka is offline luka  Slovenia
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I have used it with my own... nothing speacial, like one would use normal trafo
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Old 25th March 2010, 10:36 PM   #4
mlloyd1 is online now mlloyd1  United States
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a search would eventually turn up this link:

Switchmode Power Supply For Car Audio

some useful info but not quite a complete design ....

mlloyd1
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Old 27th March 2010, 02:13 AM   #5
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is this smps is suitable for my project..?
it is 50-0-50v, how can i modify this to 35-0-35v..?
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File Type: jpg schematic.jpg (96.9 KB, 1578 views)
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Old 31st March 2010, 03:49 PM   #6
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Anybody please help... how can i modify the above smps in to 35v-0-35v
(is that possible to change feed back zener diode ratings to reduce the output voltage...?)

Is this smps suitable for audio amps..?
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Old 1st April 2010, 12:56 AM   #7
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by pradeeppk View Post
is this smps is suitable for my project..?
it is 50-0-50v, how can i modify this to 35-0-35v..?
I can't read the schematic, it's blurry with small text. But look like a couple zeniers down at the bottn used as a voltage reference. Change their value as required.
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Old 2nd April 2010, 04:50 PM   #8
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Quote:
Originally Posted by ChrisA View Post
I can't read the schematic, it's blurry with small text. But look like a couple zeniers down at the bottn used as a voltage reference. Change their value as required.
Here is the schematic in pdf format.

what about changing secondary winding to change voltage to 32-0-32v ...?

if i have changed what will happen to output current..?

is there any modification need for control section..?

anybody pls HELP...
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File Type: pdf smps_ver2 (1).pdf (26.0 KB, 557 views)
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Old 2nd April 2010, 08:09 PM   #9
stoc005 is offline stoc005  United States
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The each secondary has 9 turns. Needs to be reduced to 8 or 7 turns. The zeners in the opto circuit have to be reduced to ??. YGM. But, I've seen this PS schematic before in power supply forum. Perhaps the designer can help you out. Other than that, it may work.
Personally, I'd buy Meanwell SMPS off Ebay.
connexelectronic.com has a 1KW in a kit form and a 350-450W smps for 50 USD. See if they might do the job as well. Yes, you can save money by buying a blank PCB and chasing all the parts, winding the transformer(s) but it takes a bunch of time and work.
Good luck.
BTW, what's wrong with a 50/60Hz transformer supply??
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Old 3rd April 2010, 10:02 AM   #10
joaquim is offline joaquim  Sweden
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I can understand why you wanna use a switch-mode pwr-supply if u have "space" issue or you're to cheap to by a linear solution. I've build a surround system with LM3886, just 'cuz they are well-designed and very few external parts is needed. So the Amp becomes very compact, I've also use the same IC in active speakers. Using SMPS with audio is not recommended, though you will get ripples how well designed SMPS you'll use. Those who builds class-D amp's, knows that converting the pulses into clean sinus is almost impossible, SMPS are o the march, especially in hi-watt PA-systems, were the sound quality isn't the deciding factor, you want people to hear you, and if it sounds good is just a bonus . It's not like leaning back in your favorite chair or sofa and put on Gary Moore, on vinyl...
So why you want to "distort" a good audio-ic with a smps is beyond me... LM3886 is a B-Amp, so you have a quite high efficiency - 85% - 90% - so you wanna use a transformer listed for 150VA, and 25A rectifier and two 10mF(or one 22mF)/channel, and maybe two three 0R15/10W resistors in parallel, in +V and -V, to further suppress eventual ripples, like;

----C(10mF) --- R (0R075)----C(10mF)---> + 35V(-35V)

as simple as they come... But if you up for a challenge and loooong nights, go ahead w/ your SMPS(U).... I'd never use SMPSU in a audio application, RF, pulses, digital designs etc. then they make life easier, but try to build a 20W rms A-amp with a switch-mode supply..... I, like my 'guru' John L Hood(who sadly died a few years ago) am very fond of the class-A amplifier, you have none of the drawback that B, D, T etc has, the major drawback though is the low efficiency, only 20 - 25%, so you'll need 100W of power to get 20W from the amplifier, but you don't have to consider the phase, and you can achieve a well-sounding amp with very few components.... but opinions are like 'behinds'; everybody has one....
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