Power Amp P.S. Bleeder Resistor Reg? - diyAudio
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Old 27th April 2008, 12:13 AM   #1
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Default Power Amp P.S. Bleeder Resistor Reg?

Hello to All!

I have read about power amplifier designs with traditional
rectifier/capacitor power supplies that used power resistors
across the large caps to intentionally create a constant load
on the power supply (not the usual bleeder resistor function).
This was done as a way of reducing the power supply voltage fluctuation with current demands from the output stage. Is this
a viable approach that could be added to a power supply to
improve performance, and if so, how great would the constant
load have to be?

Many Thanks In Advance.

fastcat95
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Old 27th April 2008, 03:20 PM   #2
AndrewT is offline AndrewT  Scotland
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no,
extra load increases the ripple of the PSU, not reduces fluctuations.
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regards Andrew T.
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Old 28th April 2008, 06:10 AM   #3
gain is offline gain  United States
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YES IT IS A GOOD IDEA! from a safty standpoint its a MUST! a bleeder resistor across a big cap prevents it from storing large amounts of charge for long periods of time. the caps used in the PS's of power amps typically run 4700 - 20000 uF or more. besides being able to maintain the potentially lethal rail voltages across them for days or weeks, capacitors of that size when charged will instantly vaporize any conductive item that happens to fall between its terminals. or it may explode instead, injuring or possibly killing someone who is working on the amp. (this can especially happen when the amp board fails or is disconnected for testing purposes, because then there is no load to discharge the caps when the power is turned off)

please, by all means install bleeder resistors across reservoir capacitors! it may save someone's life someday. use ohm's law and RC time constant to choose a resistor that will totally discharge the cap within about thirty seconds or so after removing power with no load connected to the power supply.
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