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Old 27th March 2007, 06:03 PM   #1
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Location: Cheshire
Default Basic ground and earth questions

I am putting together in one case, a Marantz CD63SE, a Monica2 DAC, a line level preamp, a Charlize T-amp, and an SMPS (to power dac, pre and power amps).

My question is this (very obvious and basic if you know): Are the line level signal grounds meant to be all connected together (between CDP and dac, between dac and preamp, between preamp and poweramp). Also are these to be connected to the 240v earth that is used by the SMPS and CDP?

What potential problems are there?
How do I avoid ground loops?
Any tips greatfully received.

I am sure that this is covered elsewhere, but simple questions are hard to search and find.
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Old 28th March 2007, 05:39 AM   #2
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Join Date: Sep 2006
If all of the inputs are differential, there won't be any noise and signal grounds definitely should be tied together. I would assume signals are either internally tied to earth ground or intentionally floated and would not attach them externally.
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Old 28th March 2007, 06:28 AM   #3
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Hi,
is the CDP earthed with a three core cable?

The safety earth system is there solely to protect the user in the event that a fault develops in the equipment. It is NOT there to make the audio system quieter nor work better. In many instances the safety earth makes the performance of the audio system worse.

The audio ground in the equipment is part of the flow and return circuit both internally and to other connected equipment. This flow and return is fundamental the the way electricity flows around a circuit (note; circuit). The audio will work perfectly well without any connection to the safety earth.

There is a very important condition.

All exposed conductive parts MUST be connected to the safety earth.
This over-rules the audio requirement to float the ground system completely separate from the safety earth IF there are any metal parts that can be touched by the user.

I recommend a disconnecting network between the safety earth and the floating audio ground rather than a direct ultra low resistance connection.
The disconnecting network can consist of any combination of the following :-
Power resistor,
Power diode bridge,
Power thermistor.

Additonally a high frequency capacitor may make the system quieter. A switch to short across this network to effect a direct connection could be fitted (this is the ground lift switch occassionally found on equipment- the ground lift switch MUST NOT BREAK the connection between safety earth and audio ground).
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regards Andrew T.
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