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Old 11th January 2014, 10:33 PM   #1
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Default filter resistors location on a single capacitor PS

Hi
I start to build the F5 amplifier power supply according to the schema blow:
I bay only single 47000uf (for + and another for -), where I need to put the resistors (R1-4) with my only single cap?
thanks
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Old 11th January 2014, 10:59 PM   #2
eyoung is offline eyoung  United States
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Hi...

I would forget about R1-8 keep the 2.2k resistors in place and by pass my big caps with a mylar or poly 1.0uf cap each lets see what the greedy boyz think...

regards, Elwood
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Old 12th January 2014, 12:20 AM   #3
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Locate the paralleled resistors between the rectifier bridge and your single large filter cap. so they form an low-pass filter. This will also limit the current surges drawn in charging the capacitor.
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Last edited by Ken Newton; 12th January 2014 at 12:30 AM.
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Old 12th January 2014, 12:55 AM   #4
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Split the cap?
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Old 12th January 2014, 05:53 AM   #5
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I can't split the cap, already bay it
More suggestions?
maybe put more cap (10,000uf) in parallel to the 47,000uf and between them put the R1-8?
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Old 12th January 2014, 11:36 AM   #6
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Quote:
Originally Posted by erez1012 View Post
I can't split the cap, already bay it
More suggestions?
maybe put more cap (10,000uf) in parallel to the 47,000uf and between them put the R1-8?
Yes you can, just have to believe in it. By the way,these resistors, they are current limiters. If your bridge can tolerate inrush start up current, than what is the point?
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Old 12th January 2014, 02:03 PM   #7
DF96 is offline DF96  England
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Those same resistors placed before the first cap will drop more voltage, as the charging pulses have a much higher peak value than DC. Either build it as it is, or redesign it.
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Old 12th January 2014, 06:08 PM   #8
CBS240 is offline CBS240  United States
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The idea of the circuit is a CRC filter. The charging current pulses from the transformer must be separate from the amplifier currents. The first C is the filter capacitor. The second C is the capacitor bank. These are separated by a small R. The return current path for the first set of capacitors should go to the transformer CT. The return currents for the second set of capacitors after the R should be separate leading back to the star ground point. The star then connects to the transformer CT. Half as$ building the power supply may lead to noise and Bzzzzzz, along with frustration. A power amp is only as good as it's power supply.
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Old 12th January 2014, 07:09 PM   #9
DF96 is offline DF96  England
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No transformer CT here. Two secondaries feeding two bridges.

There won't be a lot of filtering from the resistors. 15mF at 120Hz is 0.09R (plus ESR). Four 0.47R in parallel is 0.12R. I calculate roughly 4dB of extra smoothing at 120Hz, although more at higher frequencies. Given that this is less than the 6dB extra from simply paralleling the caps the reality may be somewhere around 7 or 8dB? PSUD2 may help.
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Old 12th January 2014, 10:37 PM   #10
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Thanks guys for good explanation (and complex).
Now do I have to bay more cap?
And if I have to bay, 10000uf is ok (I don’t have budget for more 47000uf)
thanks
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