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Old 12th May 2003, 04:02 PM   #21
joensd is offline joensd  Germany
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Quote:
paulb,

Then would adding 2 resistors as a voltage divider suffice to create the split rails?


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Well somehow it would. Never tried it with a poweramp and I think its not the way to go.
Works "well" with a headphoneamp.
BTW:Where are the +-23V coming from?
I think youd still get around 46.5V.

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Jens
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Old 12th May 2003, 04:03 PM   #22
moamps is offline moamps  Croatia
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hi,
your half wave rectifier can work teoreticaly. You put 3ohm resistor and get huge current, biiiiiig ripple, and small, teoreticaly good DC voltage on output (18V).

Better (and I think only practical) solution with this transformer is using stabilizated power supply.

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Old 12th May 2003, 04:11 PM   #23
joensd is offline joensd  Germany
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Just looked it up to be sure:
One way rectifying will give you about VDC=1,2*VAC=39,6V.
So wheres the +-23V and the 18V coming from?????

Jens
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Old 12th May 2003, 04:52 PM   #24
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zx3chris,

Your simulations are way off. What you are simulating is the case where the load is overcoming the capacitance, and that's why your DC voltage is lower than VAC*2^0.5.

Simulate the "one way symmetric" example with big capacitors and ignoring one of the outside taps.
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Old 12th May 2003, 05:51 PM   #25
joensd is offline joensd  Germany
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Quote:
VAC*2^0.5
VAC*(2^0.5)
Before anybody gets confused calculating like mad.

Jens
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Old 12th May 2003, 06:24 PM   #26
paulb is offline paulb  Canada
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Quote:
Originally posted by joensd

Well somehow it would. Never tried it with a poweramp and I think its not the way to go.
Works "well" with a headphoneamp.
BTW:Where are the +-23V coming from?
I think youd still get around 46.5V.

Regards
Jens
A voltage divider approach would only work properly if the current from the ground terminal is much less than the current through the divider resistors.
You may be able to get away with it by using big caps across the divider resistors (as in the "Cmoy" headphone amp), but I still think you'd have to waste a lot of heat in the resistors for it to work properly.
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Old 12th May 2003, 09:52 PM   #27
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i did do simulation with big capacitors and the voltage approaches 46v--i was trying to get a lower dc voltage, which i can do this way but it isnt steady--i need a better tranny or a chip that can take a higher voltage

-chris
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Old 12th May 2003, 10:27 PM   #28
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zx3chris,

I can't say it many more times: ignore 1 of the transformer taps. And read how many other posters have said that too.

When you put on big caps, the supply behaves properly...so you approach 33VAC*(2^0.5) which is where your 46 is coming from.

By putting on small caps to intentionally drop the DC, you are creating a wickedly poor supply that will not do a good job because the DC voltage is jumping around like crazy if looked at on a small time scale.

If you use the "one way symmetric" example with big caps, you will get about 46 volts...but as 2 rails of +/- 23V.
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