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Old 9th October 2006, 08:11 PM   #61
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I think that would give you +-56V rails, not 28V.
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Old 9th October 2006, 09:36 PM   #62
john65b is offline john65b  United States
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If you have a 20V - 20V toroid on the AC side of a rectifier, you get the same as a 40V - 0V on the AC side of a rectifier, which is +/- 28VDC.

I tried it...
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Old 9th October 2006, 09:50 PM   #63
AndrewT is offline AndrewT  Scotland
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NO!
If you use 20-0-20 then you get +-28Vdc because the 0V gives a reference.

The 40-0 gives 56Vdc and there is no 0V reference to split the 56Vdc in half.

You have been advised (by others) to avoid using a virtual earth for the power amp.
I now concur with this advice.
The reason I arrive here is that you would require a high current power amp to generate the virtual earth and having generated it artificially there is no guarntee that it will sound nice or even work stabily. A lot of development time and cost to avoid rewinding or buying a transformer.
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Old 9th October 2006, 10:51 PM   #64
john65b is offline john65b  United States
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Very well. I will leave it alone.
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Old 10th October 2006, 02:45 PM   #65
john65b is offline john65b  United States
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Yes, after reading AndrewT's response again, I see my mistake. The 40V-0V secondary has no center reference to get the values I am seeking.

To total voltage across the AC pins of a rectifier may be the same from 20V 20V (centertapped case) versus a 40V 0V (standalone secondary case), but output voltages are referenced from different points...

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