Ripple and chokes - Page 2

Tom Bavis · 12th April 2006, 07:54 PM

With a ground at the (-) input of the chokes and at the (-) output they are shorted... unless one of the two ground symbols isn't connected anywhere...

Normally in this circuit, the ground is at the output of the filter, and the (-) input floats at some volts negative. A small additional R-C filter in the (+) lead (just a resistor - capacitor is already there) can take care of any noise that is coupled through common mode or via the choke's capacitance to ground.

cerrem · 12th April 2006, 09:15 PM

If you use a "common" choke in the neg to ground side of the power supply...you then disturb the ground for all the rest of the circuits.. You now introduce a ripple in ground ...so the ground is bouncing.... This may be fine in RF equipment...but in Hi-End audio the sensitive pre-amp stages will have a noisey ground as reference..

Chris

Gluca · 12th April 2006, 10:07 PM

Thanks.

Tom signal ground (see the scheme) is not connect to anything so choke is not shorted. I elected to connect to earth the (-) lug of the first cap (that's is the input to the first choke) for safety reasons.

Cerrem, not sure I got your idea properly ...

Gianluca

Dave Cigna · 12th April 2006, 10:33 PM

What you have labeled signal ground is the 'real' ground. If you want to connect your chassis anywhere it should be there, otherwise your signal ground will be bouncing around relative to the chassis (earth.) You can make the connection to the chassis through a small value resistor; that's up to you. I've never found the resistor necessary unless there were other grounding problems like ground loops.

Where to connect the cathodes? Obviously to signal ground in any case.

Gluca · 12th April 2006, 11:01 PM

OH! Thanks all! So I was given a wrong suggestion ... I was told to tie to ground the first cap and let the cathode (signal etc...) return to the "floating" end of the last choke/cap.

I'll do that... I just need to swap a wire.

Gianluca (much happier now)

7n7is · 12th April 2006, 11:18 PM

What do you think of this arrangement?

http://www.decware.com/cgi-bin/yabb/...num=1131291437

Geek · 13th April 2006, 01:05 AM

Quote:

Originally posted by 7n7is
What do you think of this arrangement?

http://www.decware.com/cgi-bin/yabb/...num=1131291437

I think it's a great way to end up killing yourself

This is a common-mode filter. You'll not find a 10H (or whatever) common-mode choke unless you roll it yourself.

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12th April 2006, 07:54 PM	#11
Tom Bavis diyAudio Member Join Date: Jun 2002 Location: Macedon NY	With a ground at the (-) input of the chokes and at the (-) output they are shorted... unless one of the two ground symbols isn't connected anywhere... Normally in this circuit, the ground is at the output of the filter, and the (-) input floats at some volts negative. A small additional R-C filter in the (+) lead (just a resistor - capacitor is already there) can take care of any noise that is coupled through common mode or via the choke's capacitance to ground.

12th April 2006, 09:15 PM	#12
cerrem diyAudio Member Join Date: Jun 2005 Location: San Diego, CA	If you use a "common" choke in the neg to ground side of the power supply...you then disturb the ground for all the rest of the circuits.. You now introduce a ripple in ground ...so the ground is bouncing.... This may be fine in RF equipment...but in Hi-End audio the sensitive pre-amp stages will have a noisey ground as reference.. Chris

12th April 2006, 10:07 PM	#13
Gluca tarmac ripper diyAudio Member Join Date: Nov 2004 Location: Back to Italy	Thanks. Tom signal ground (see the scheme) is not connect to anything so choke is not shorted. I elected to connect to earth the (-) lug of the first cap (that's is the input to the first choke) for safety reasons. Cerrem, not sure I got your idea properly ... Gianluca

12th April 2006, 10:33 PM	#14
Dave Cigna diyAudio Member Join Date: Oct 2003 Location: Finger Lakes, NY	What you have labeled signal ground is the 'real' ground. If you want to connect your chassis anywhere it should be there, otherwise your signal ground will be bouncing around relative to the chassis (earth.) You can make the connection to the chassis through a small value resistor; that's up to you. I've never found the resistor necessary unless there were other grounding problems like ground loops. Where to connect the cathodes? Obviously to signal ground in any case.

12th April 2006, 11:01 PM	#15
Gluca tarmac ripper diyAudio Member Join Date: Nov 2004 Location: Back to Italy	OH! Thanks all! So I was given a wrong suggestion ... I was told to tie to ground the first cap and let the cathode (signal etc...) return to the "floating" end of the last choke/cap. I'll do that... I just need to swap a wire. Gianluca (much happier now)

12th April 2006, 11:18 PM	#16
7n7is diyAudio Member Join Date: Mar 2006 Location: VA	What do you think of this arrangement? http://www.decware.com/cgi-bin/yabb/...num=1131291437

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