Filtering out Power Supply Noise

zenon · 31st October 2006, 02:57 AM

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

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

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.

AndrewT · 2nd November 2006, 06:46 AM

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.

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

Hi,
the diagram is already "here".

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

31st October 2006, 02:57 AM	#1
zenon diyAudio Member Join Date: Nov 2004 Location: here	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

31st October 2006, 01:49 PM	#2
harvardian diyAudio Member Join Date: Dec 2001 Location: Austin, TX	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. __________________ doing my part to Keep Austin Wierd.

2nd November 2006, 06:46 AM	#6
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	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. __________________ regards Andrew T.

2nd November 2006, 05:50 PM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the diagram is already "here". But maybe it wants to go somewhere in Canada, or is that where you would like to be? __________________ regards Andrew T.

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31st October 2006, 10:27 PM	#3
lndm diyAudio Member Join Date: Mar 2006 Location: nsw	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.

2nd November 2006, 02:01 AM	#4
ew diyAudio Member Join Date: Jan 2005 Location: n/a	could a rc filter be used to knock the voltage down by 2-4volts?

2nd November 2006, 04:56 PM	#7
zenon diyAudio Member Join Date: Nov 2004 Location: here	Andrew, can you make a diagram of what you mean? I don't know how that would be wired etc.

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