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Old 30th March 2008, 12:35 AM   #1
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Default Power supply issue

I was wondering if anyone has tried to make a split supply(+/-) from a single non-center tap output transformer. I bought a transformer from Parts Express (129-075), and I was hoping to do just that. Now I know the once I rectify the AC and use 2 equal value caps in series a cross the output, my voltage is cut and half. Sound prefect right , however when I load the circuit, I end up more voltage on side or the other? I'm looking to get +/- 22v for a pair of TDA2052. My source for the transformer is :32v(which is what I what to divide in half and then regulate), 16V-0-16v, 12v AC

any ideas?
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Old 30th March 2008, 01:38 AM   #2
TheMG is offline TheMG  Canada
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You need a transformer with either a center tap, or dual secondary windings.

Otherwise your circuit ground is floating and will drift when a load is applied unequally to the rails of the supply, as you've found out. You can get away with it for very low-power applications, but not for a power amp.
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Old 30th March 2008, 01:42 AM   #3
gootee is offline gootee  United States
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It could be done. But it would probably be best to just use two suitable transformers, or a transformer with suitable dual secondaries.

If you really don't want to buy another transformer, you 'might' be able to use a power 'rail splitter', which would take your approximately 43.6v and split it into +/- 21.8v and create a new 'virtual ground' between the two new power rails. You could rectify and filter (and maybe regulate, if +/-20v or so is good-enough) your existing transformer's output and then use a circuit similar to the one shown in the LM675 datasheet at national.com. You would need to use a chipamp that could handle the current and voltage, etc etc, instead of the LM675.
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Old 30th March 2008, 05:01 PM   #4
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Default rail splitter?

Do you know I would find a sample circuit?
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Old 30th March 2008, 05:42 PM   #5
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what about running the TDA from a single supply?
That would spare you from a lot of headaches.
Regards
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Old 30th March 2008, 05:45 PM   #6
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Default this is true

I was looking at that but didn't find a circuit for a single sided TDA2052 amp?
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Old 30th March 2008, 08:00 PM   #7
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sorry, I mixed it up with TDA 2050
the attached circuit should work. But I haven't tried it personally.
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