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Old 1st May 2011, 03:19 PM   #1
Beranga is offline Beranga  Mexico
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Default Grounding chassis through RCA

Thanks you for bearing with me and my newbee question:

I have a DAC-Pre-Amp setup with ground loop issues that go away when using cheater plugs on the DAC and Pre, and leaving only the Amp safety grounded. I understand this setup is dangerous, my question is:

As I understand it, the path to ground of the cheater plugged equipments is though the shield of the RCA cables connecting them to the grounded Amp, and that shield will probably not hold in case one of the ungrounded chassis goes live, but what if I make an RCA interconnect with no signal wire, only the shield consisting of a 10AWG wire? would it make my setup safe?

I have checked conductivity with a DVM and it seems that the RCA grounds, the chassis and the safety grounds, are connected inside on all three equipments with a thick bare copper wire.

I guess connecting all chassis directly by screwing the 10AWG wire is another alternative, but using the RCA plugs would be more practical. Would this be a much better way to do it?
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Old 2nd May 2011, 12:00 AM   #2
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Instead of doing the above, why don't you lift the grounds from the chassis? Add a 33-50 ohm high wattage (20W-100W) resistor from the power earth/ground wire to the chassis for all three of your equipment. This will still maintain safety and prevent/reduce ground loops.
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Old 2nd May 2011, 12:49 AM   #3
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The earth through the RCA socket should be switched so depending what is connected you have it or leave out the connection to ground.
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Old 2nd May 2011, 06:13 PM   #4
Beranga is offline Beranga  Mexico
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Quote:
Originally Posted by quikie22 View Post
Instead of doing the above, why don't you lift the grounds from the chassis? Add a 33-50 ohm high wattage (20W-100W) resistor from the power earth/ground wire to the chassis for all three of your equipment. This will still maintain safety and prevent/reduce ground loops.
I will try that, thank you.
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Old 2nd May 2011, 08:39 PM   #5
tomchr is offline tomchr  United States
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A ground separator would do the job better than the resistor. See D1, D2, R1, C1 of the first figure on this page.

~Tom
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Old 3rd May 2011, 03:44 AM   #6
Beranga is offline Beranga  Mexico
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Quote:
Originally Posted by nigelwright7557 View Post
The earth through the RCA socket should be switched so depending what is connected you have it or leave out the connection to ground.
The RCA plugs in my equipment are ground interconnected with a thick copper wire/bar, only the signal is switched with the input selector.
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Old 3rd May 2011, 12:59 PM   #7
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Quote:
Originally Posted by Beranga View Post
The RCA plugs in my equipment are ground interconnected with a thick copper wire/bar, only the signal is switched with the input selector.
As is on most equipment unless its monobloc designed or monobloc in same chassis.
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Old 3rd May 2011, 01:03 PM   #8
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Quote:
Originally Posted by tomchr View Post
A ground separator would do the job better than the resistor. See D1, D2, R1, C1 of the first figure on this page.

~Tom
Why would this work better than a simple resistor and capacitor? I understand the role of the capacitor, which I would also include.
But the diodes? What does he mean by a "major problem"?

I think the resistor value shown is actually a little too low. I would still stick to something in the region of 30-100 ohms.

Last edited by quikie22; 3rd May 2011 at 01:06 PM.
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Old 4th May 2011, 02:55 AM   #9
Beranga is offline Beranga  Mexico
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Quote:
Originally Posted by quikie22 View Post
...why don't you lift the grounds from the chassis? Add a 33-50 ohm high wattage (20W-100W) resistor from the power earth/ground wire to the chassis for all three of your equipment.
Quote:
Originally Posted by tomchr View Post
A ground separator would do the job better than the resistor. See D1, D2, R1, C1 of the first figure on this page
Thanks for the quick responses, I've another question:

Could the resistor/network mentioned be connected between the earth wire and the chassis? or would the chassis need to be directly connected to earth and the resistor/network before the rest of the circuit?

I´m confused because in the ground separator schematic, it looks like there is a connection to the chassis before the R-C-Diode network and I don´t understand why.
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Old 30th May 2011, 01:45 PM   #10
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Beranga View Post
Could the resistor/network mentioned be connected between the earth wire and the chassis? or would the chassis need to be directly connected to earth and the resistor/network before the rest of the circuit?
Good point.

Should we connect the chassis to Earth and the circuit V0 to the resistor ?
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