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Old 9th July 2012, 03:50 AM   #1
Le Pick is offline Le Pick  Canada
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Default Negtive Voltage ?????

Hi, I'm making an amplifier based on the L12-2 amp and a 6N3 Buffer Pre Amp. And I've also bought an toroidal transformer (25-0-25). But the thing is that I'm not quite sure how to make an output of -50VDC / GND / +50VDC for the amplifier.

I've came across this schematic :

Click the image to open in full size.

So let's say that my transformer is wired in series, giving me an output of 50VAC, sending that voltage in a bridge rectifier and make a this negative voltage generator (like the picture). Is the output of the generator going to be -25VDC / GND / +25VDC or -50VDC / GND / +50VDC (Assuming that the picture below is the roughly made schematic without filter caps)???
Click the image to open in full size.

Thanks

Le Pick
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Old 9th July 2012, 06:17 AM   #2
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TBH, those schematics look like a train wreck to me.
The only way I know of to obtain 50-0-50 from a 25-0-25 transformer is via a voltage doubler type of circuit.
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Old 9th July 2012, 12:03 PM   #3
Le Pick is offline Le Pick  Canada
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But is making a voltage doubler will lower the amps ?
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Old 9th July 2012, 12:29 PM   #4
Le Pick is offline Le Pick  Canada
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I've also came across THIS power supply. Assuming that I put 50VAC in the input, will i still get -50VDC / GND / +50VDC as output ?
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Old 9th July 2012, 06:18 PM   #5
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^^See post #2.
Have a closer look at those schematics. You'll see that the regulators are acting on the exact same input voltage, with only the polarity signs reversed. And so while the voltage between GND and one output will be correct, the voltage between GND and the other output will only be the voltage drop across that regulator.
Yes, a doubler will lower the current delivered. You really need a transformer bigger than 35-0-35.
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Old 9th July 2012, 06:50 PM   #6
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This is a dual thread of a 50V PSU question that has already been addressed.

50V Power Supply
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Old 9th July 2012, 07:58 PM   #7
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True, but this is the original thread.
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Old 10th July 2012, 04:42 AM   #8
Le Pick is offline Le Pick  Canada
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Quote:
Originally Posted by KatieandDad View Post
This is a dual thread of a 50V PSU question that has already been addressed.

50V Power Supply
Indeed, because I had another idea and also the other thread have more replies...
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Old 10th July 2012, 05:02 AM   #9
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Hi , you can keep the 25-0-25 V AC trafo for future projects .
The bridge rectifier + lots of caps may not be optimal , a big fat cap
is also visually more ' muscular'
Look for 10000 uF / 63 VL for a 50 V DC application ( there are the surge peaks and the variations of the mains )
Also 15-20 K uF ...you just need two , one for positive rail and one for neg.
The bridge rectifier could be the square 25 A with faston type pins .

Last edited by picowallspeaker; 10th July 2012 at 05:07 AM.
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