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Old 31st October 2006, 02:57 AM   #1
zenon is offline zenon  Canada
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Default Filtering out Power Supply Noise

I read some posts on the Power Supply forum about actively "filtering" out noise from power supplies. They referenced this site:
http://www.wenzel.com/documents/finesse.html

Has anyone tried to do something like this for Chip Amps??
Any ideas why it may/may not work??

TIA
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Old 31st October 2006, 01:49 PM   #2
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Certainly possible

1) Most of the chip amps have decent PSRR anyways.

2) You would need to scale for the current. May need to heat sink the pass device.
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Old 31st October 2006, 10:27 PM   #3
lndm is offline lndm  Australia
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If you're considering a 1 ohm series resistor, a simple RC made of the resistor and 10,000uF of capacitance is going to give you a few dBs better filtering, or even 2 ohms, or two stages. The series resistor may even relax ringing in the electrolytics, if there is any. Just a thought.
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Old 2nd November 2006, 02:01 AM   #4
ew is offline ew  United States
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could a rc filter be used to knock the voltage down by 2-4volts?
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Old 2nd November 2006, 06:07 AM   #5
lndm is offline lndm  Australia
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Quote:
Originally posted by ew
could a rc filter be used to knock the voltage down by 2-4volts?
Yes, but this is more sucessful with an amp that has a more constant draw of current. It is often done with class A amps. You could make sure you had a large enough cap after the dropping resistor but that'd average out the drop which would be less at amp idle, and more under heavy use.

A regulator would be a more consistent way to burn some volts, if you can afford the volts.
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Old 2nd November 2006, 06:46 AM   #6
AndrewT is online now AndrewT  Scotland
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Hi,
or try a capacitance multiplier in lieu of the regulator, or maybe even the resistor.

If going for RC then it would be more effective if it were
R/2 , 2C , R/2 , 2C , but at the considerable cost of four times as much capacitance.
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Old 2nd November 2006, 04:56 PM   #7
zenon is offline zenon  Canada
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Andrew, can you make a diagram of what you mean?
I don't know how that would be wired etc.
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Old 2nd November 2006, 05:50 PM   #8
AndrewT is online now AndrewT  Scotland
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Hi,
the diagram is already "here".

But maybe it wants to go somewhere in Canada, or is that where you would like to be?
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