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Old 18th September 2003, 09:34 PM   #1
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Default Ground connections across multiple components

Hi,

So... assuming everything here is built using 3-prong power cables. When you build an amp (or preamp, or CD player, or whatever), the chassis always connects to the 3rd prong, and that is done close to the IEC socket (or power cable entry point), right? This earths the chassis, and ensures that if the power supply ever shorts to the chassis, that'll blow the fuse. So, no compromises here.

Then you have the ground/0V reference in the actual circuitry, which usually includes the power supply and the audio/signal circuitry (I'm thinking of tube amps here, but I think they'll have to share a 0V reference in any setup). This is usually also connected to the chassis, and that is done close to the input stages so that the enclosure is closer to 0V near the input stages (something to do with shielding and leakage capacitance or something, I don't fully understand it but I've seen the difference on my scope).

OK so far? Please correct any errors in the previous statements, because that'll probably answer the questions below.

OK, now we come to multiple components hooked up through interconnects. And since these are DIY components, we're free to implement our own grounding scheme. What's the best way to implement a system-wide grounding scheme? I think the chassis in each component should still be connected to safety earth. This is essential, in order to avoid shock hazards from the chassis. But the audio circuitry, wouldn't it be better if that referenced safety earth in only one component? Either the most upstream, or the most downstream? Otherwise if 0V in every component is connected to the chassis (and hence to safety earth), isn't that a potential ground-loop situation?

Have any of you implemented 'system-wide star earthing' or anything like that? Or a system where the grounds of the upstream component flow to the downstream component which eventually connects to safety earth at one point? Or maybe in the other direction, grounds flow upstream, sine it's your phono stage where you want the lowest voltage difference between chassis and 0V.

I'm sure there are other ideas that I haven't considered. If someone has done anything along these lines, I'd appreciate ay advice and/or pointers.

Thanks,
Saurav
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Old 18th September 2003, 09:45 PM   #2
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Quote:
What's the best way to implement a system-wide grounding scheme?

Grumble, grumble. Much as I hate to admit it, Steve Eddy has me convinced that the best way is to galvanically isolate each component, and have the chasses grounded through the individual line cords. That means properly balanced input transformers. That means a lot of money.

In my own experience, I'll only connect one component to earth ground, letting the others be grounded through the interconnections (easy for me, because only one of my components has a three-wire plug). When I've done otherwise, I've often run into loop problems. Now, this has resulted in some shock-tickle situations when hooking up my satellite box, but I've learned to carefully connect the chassis of that box and my preamp together temporarily until everything else is plugged in.
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Old 18th September 2003, 09:58 PM   #3
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> is to galvanically isolate each component

Sorry, I'm lost. What exactly does that mean?

> That means properly balanced input transformers. That means a lot of money.

Well, it'll be a while before my system is balanced all the way through (that is, if I ever get there).

> In my own experience, I'll only connect one component to earth ground, letting the others be grounded through the interconnections (easy for me, because only one of my components has a three-wire plug).

Let me see if I understand you right. On one component the chassis connects to earth ground (and audio 0V), on all the others the chassis connects to 0V, which gets carried across on the interconnect's ground lead. Is that correct?

> When I've done otherwise, I've often run into loop problems. Now, this has resulted in some shock-tickle situations when hooking up my satellite box, but I've learned to carefully connect the chassis of that box and my preamp together temporarily until everything else is plugged in.

Well then, how about running separate wires connecting the chasses together? Every RCA connector is isolated from its chassis. The interconnects connect the adio circuitry in all components together, and the other wire connects all chasses together. Both 'sets of grounds' meet in one component.

The only risk I see here is when something is disconnected, then you'll have components where 0V and earth ground aren't connected. I'm not sure if that's a safety hazard or not.
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Old 18th September 2003, 10:07 PM   #4
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See this paper, for a readable, understandable overview of the problem: http://www.jensentransformers.com/an/an004.pdf

And the specific transformers I'm using: http://www.jensentransformers.com/datashts/11p1.pdf

Steve's site shows how pretty you can make this- and touts the advantages: www.q-audio.com
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Old 18th September 2003, 10:14 PM   #5
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Thanks.
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