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zenon 31st October 2006 02:57 AM

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:

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


harvardian 31st October 2006 01:49 PM

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.

lndm 31st October 2006 10:27 PM

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.

ew 2nd November 2006 02:01 AM

could a rc filter be used to knock the voltage down by 2-4volts?

lndm 2nd November 2006 06:07 AM


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.

AndrewT 2nd November 2006 06:46 AM

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.

zenon 2nd November 2006 04:56 PM

Andrew, can you make a diagram of what you mean?
I don't know how that would be wired etc.

AndrewT 2nd November 2006 05:50 PM

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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