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Old 12th April 2006, 07:54 PM   #11
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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.
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Old 12th April 2006, 09:15 PM   #12
cerrem is offline cerrem  United States
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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
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Old 12th April 2006, 10:07 PM   #13
Gluca is offline Gluca  Italy
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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
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Old 12th April 2006, 10:33 PM   #14
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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.
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Old 12th April 2006, 11:01 PM   #15
Gluca is offline Gluca  Italy
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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)
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Old 12th April 2006, 11:18 PM   #16
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What do you think of this arrangement?

http://www.decware.com/cgi-bin/yabb/...num=1131291437
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Old 13th April 2006, 01:05 AM   #17
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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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