Negtive Voltage ?????

Le Pick · 9th July 2012, 03:50 AM

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 :

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)???

Thanks

Le Pick

sofaspud · 9th July 2012, 06:17 AM

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.

Le Pick · 9th July 2012, 12:03 PM

But is making a voltage doubler will lower the amps ?

Le Pick · 9th July 2012, 12:29 PM

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 ?

sofaspud · 9th July 2012, 06:18 PM

^^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.

KatieandDad · 9th July 2012, 06:50 PM

This is a dual thread of a 50V PSU question that has already been addressed.

50V Power Supply

sofaspud · 9th July 2012, 07:58 PM

True, but this is the original thread.

Le Pick · 10th July 2012, 04:42 AM

Quote:

Originally Posted by KatieandDad

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...

picowallspeaker · 05:07 AM

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 .

9th July 2012, 06:18 PM	#5
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio	^^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. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

9th July 2012, 07:58 PM	#7
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio	True, but this is the original thread. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

10th July 2012, 05:02 AM	#9
picowallspeaker diyAudio Member Join Date: Apr 2007	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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9th July 2012, 06:17 AM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio	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. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

9th July 2012, 12:03 PM	#3
Le Pick diyAudio Member Join Date: Jun 2012 Location: Quebec	But is making a voltage doubler will lower the amps ?

9th July 2012, 12:29 PM	#4
Le Pick diyAudio Member Join Date: Jun 2012 Location: Quebec	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 ?

9th July 2012, 06:50 PM	#6
KatieandDad diyAudio Member Join Date: Nov 2011 Location: UK	This is a dual thread of a 50V PSU question that has already been addressed. 50V Power Supply

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