Building a power supply unit.

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S.C

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Joined 2003
Last few questions,

1. You guys said 160VA-250VA(watt) per channel will be enough "save". Does it apply to the transformer before bridge or after?

As an example,

1. a 250VA Transformer 115V Primary, 25V/25V Secondary, and 10A. Bridge: *1.414. Finally = (25*1.414)V*10A = 353.5

Or

2. a 250VA PSU, Transformer: Pri: 115V, Sec: 17.7V/17.7V, and 10A, Bridge: *1.414. Finally = (17.7*1.414)V*10A = 249.4VA?

Which one is right?

2. Does Secondary Voltage important to match the datasheet's graph? Or I just need to get enough VA(watt) rating?

Ex:

Speaker: 10 Ohm, 35W. Target Power supply 20V Power rail 26-
28V each.

Transformer A: Pri 115V, Sec 20V/20V, 12.5A
Bridge: *1.414 = (20*1.414)V12.5A = 353.5VA Per Channel

Or

Transformer B: Pri 115V, Sec 12V/12V, 20.8A
Bridge: *1.414 = (12*1.414)V20.8A = 352.9VA Per Channel

3: If I am going to have some high current transformer such as above. Can a 3.15A fuse handle it, like Nuuk's site suggested? How is fuse work?

My guess:
If it break when there is more than 3.15A go through it, then I should use higher rating fuse for those high current transformer, right?

All those through are my guessing only. Plz correct me, and my math. Feel Free to comment.:scratch:
 
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