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Old 7th April 2011, 09:27 PM   #1
Sh00pus is offline Sh00pus  United States
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Default Help Finding +/- 35V Power Supply

Dear All,

Does anyone know where I can find a good +/- 35V Power Supply schametic? I'm trying to build a Chip amp that runs off 70V. Can't seem to find any schematics on something like this.
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Old 7th April 2011, 09:38 PM   #2
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Look at Rod Elliot's Site, ESP, just scale the transformer to suit the DC voltage you want. Divide the DC voltage by the square root of two to find the AC voltage required from the transformer.
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Old 7th April 2011, 09:49 PM   #3
Sh00pus is offline Sh00pus  United States
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Would this one work? Variable Dual Lab Power Supply because it has voltage regulators in it, so that makes me kinda skeptical. And when you mean divide the DC voltage by square root of two, would that be 35V or the total 70V?
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Old 7th April 2011, 10:17 PM   #4
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Power Supply for Power Amplifiers

I would look at this one it covers the basic concepts. Those regs have a limit of 40V from their lowest to highest potential.

I was hopeing he would have a supply with a transformer with dual secondaries.


http://phonoclone.com/diy-guide.html
Look at the image under VSPS power supply to see how to handle the transformer side with 2 secondaries.

Last edited by digits; 7th April 2011 at 10:21 PM.
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Old 7th April 2011, 10:33 PM   #5
Sh00pus is offline Sh00pus  United States
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Looks perfect! Thank you. If I have anymore questions I'll be sure to post.
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Old 7th April 2011, 10:36 PM   #6
Sh00pus is offline Sh00pus  United States
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Should I take 35/sqrt(2) or 75/sqrt(2) for the voltage of AC?
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Old 7th April 2011, 10:50 PM   #7
Art M is offline Art M  United States
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Quote:
Originally Posted by Sh00pus View Post
Dear All,

Does anyone know where I can find a good +/- 35V Power Supply schametic? I'm trying to build a Chip amp that runs off 70V. Can't seem to find any schematics on something like this.

Did a quick Google for "+/- 35vdc power supply". Got 43 thousand hits. You could have a look. Must be a schematic in there some where.
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Old 7th April 2011, 10:58 PM   #8
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Quote:
Originally Posted by Art M View Post
Did a quick Google for "+/- 35vdc power supply". Got 43 thousand hits. You could have a look. Must be a schematic in there some where.
Well, that beats the purpose of this forum. As I see it, Sh00pus asked forum members for opinion and advice and he should have it. We all know how to google it B-)
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Old 7th April 2011, 11:20 PM   #9
agdr is offline agdr  United States
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Quote:
Originally Posted by Sh00pus View Post
Should I take 35/sqrt(2) or 75/sqrt(2) for the voltage of AC?
AC values are often given as the RMS (root mean square) value, which is the "power delivery" or "heating" value. When you have 120VAC coming out of your wall socket that is 120V RMS, which is really (120V)(1.414) = 170V peak [sqrt(2) = 1.414 of course]. And since the waveform is sinusoidal that is (170V)(2) = 340V peak-to-peak.

On the other side of the transformer that same magic applies but in a different way. If you have 25VAC coming out of each half of the secondary that is still 25VAC RMS, or (25V)(1.414) = 35V peak or 70V peak-to-peak. The magic here is that the filter capacitor charges to that peak value after going through the bridge rectifier, giving you around 35VDC, as long as you don't load it down more than the current rating of the transformer secondary.

Hope this helps!

Last edited by agdr; 7th April 2011 at 11:27 PM.
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Old 7th April 2011, 11:43 PM   #10
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Depending on which chipamp you are planning to build the LMXXX or LMXXXX regulators may not allow enough current to flow into the chipamp when driven hard.
A 25v-0v-25v (or 50v ct) transformer will work just fine. jer
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