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PostPosted: 02 Mar 2017, 12:12 
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Hi all,
There are many references to the necessity to ground inputs (at one end only). I guess its obvious to old hands, but for a beginner... :)

With, say, three stereo inputs there are six connectors to ground. I've shown three possibilities below.

How do folks do this in practice?


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PostPosted: 02 Mar 2017, 13:26 
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Hi,

Example 1 is most common on mid-to-high end units while #2 is seen on cheaper units (with the odd exception - like YBA)

Can't say I've seen #3

Cheers!

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PostPosted: 02 Mar 2017, 13:36 
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This is VERY rude and crude!

OK - Step back a bit, and ask yourself about what grounds do. Pretty basic.
You have heard about 'ground loops' that can cause extraneous hum and worse.
How does that happen?

Mostly by induction - if you see the ground as an antenna to any number of inductive sources, and if you understand that, typically, the larger the antenna, the stronger the received signal, then you will want to minimize the developed antenna length, in total. And minimize the number of potential inputs. Just as a radio signal *induces* signal into a radio if that analogy helps.

Of your options, 1 & 2 are much better than 3, as that provides the longest pathway to ground.

#1 is what is often described as "star" grounding - and is a common and often preferred practice. #2 is favored by bean-counters as that uses the least wire. Usually, it is some combination of both - with local "star" grounding points at various distant parts of the chassis. But - the key is that no one ground may be less efficient than any other ground - or that part of whatever it might be becomes "above ground". And that is when your troubles begin.


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PostPosted: 02 Mar 2017, 14:25 
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Thanks for the replies - interesting!

I would have gone for example 2, intuitively, as it would generally have a shorter length of ground wiring, in total, than example 1. This would presumably reduce opportunities for induction and make wiring simpler.

As an aside, moving from a circuit diagram to actually wiring the project in a practical, safe and maintenance-friendly fashion seems a REALLY big step. ( I expect you already know that; it's just sinking in for me).

Thanks again

Denis


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PostPosted: 03 Mar 2017, 04:09 
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Some reading:
http://www.analog.com/en/analog-dialogu ... unded.html

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PostPosted: 03 Mar 2017, 10:57 
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With DIY, there is always room for improvement. And you are certainly asking the right questions.


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PostPosted: 04 Mar 2017, 11:57 
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Emsworth wrote:
Hi all,
There are many references to the necessity to ground inputs (at one end only). I guess its obvious to old hands, but for a beginner... :)

With, say, three stereo inputs there are six connectors to ground. I've shown three possibilities below.

How do folks do this in practice?


At the end of the day people use what works,
Its only my opinion..

I don't believe in this ground at one end only.
As far as I'm concerned a signal has two wires, that doesn't mean one silver wire and a galvanised chassis, mains ground or the scrappiest piece of wire you can find.. :D

The signal should not use a screen as signal its a screen.
If you need to disconnect one end of an audio cable then there is something wrong.

So the whole point is to keep any differences in potential with ground circuits to a minimum.
How that's done is up to the individual..as far as I'm concerned the less wire used the less inductance and the less chance of stray capacitance / pick up. That can include a ground plane as long as there are not multiple paths for a signal and the voltage drops are graded across the plane. No cables or wires passed through it.
If the mains ground is carrying the return of the signal what's the point of using audio cables?
The ground in a system could have filters that produce ground currents and noise from computer systems, things like high integrity earthing within houses etc. Just think about X and Y capacitors as an example.
If you want to go the whole hog then switch all four wires at each input so signal and ground is switched on L & R on each input.
Then you don't have to deal with all the grounds in a system at the same time.<<its a bit pointless but some people think its the only way. another is transformer coupling.
Here is a though, if the ground from all the inputs goes to a common ground in the equipment. What's the point of having all separate wires from the ground side of the inputs? But then again whats the point of silver interconnects with copper wire after the phono plugs?
Just a few of the strange thoughts within audio..I use separate ground for left and right and then star ground at earth.
Each to their own I guess. So I don't use diagram 1,2, or 3.

I must add never disconnect a mains supply Earth to stop hum<<<<<

Here is an example for interest page 10
http://glass-ware.com/User_Guides/ACF%209-Pin.pdf

Regards
M. Gregg

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PostPosted: 04 Mar 2017, 13:05 
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For interest,

I don't use wafer switches to switch signals, I use relays.
Quad used SS switching and many people say if its good enough for quad..etc

I use a wafer switch to switch the relay coils so you don't drag the input wires to the switch.
So I just take left right and ground to the circuit.
The relays can be switched with a stepper circuit or anything realy just what ever floats your boat so to speak... :)
Here is an example:

Regards
M . Gregg


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Last edited by M. Gregg on 04 Mar 2017, 13:14, edited 1 time in total.

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PostPosted: 04 Mar 2017, 13:13 
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M. Gregg wrote:
I don't use wafer switches to switch signals, I use relays.


:thumbsup: :thumbsup: :thumbsup:

Omron G5V-2-H1 DC[x] are my go-to signal switchers :D

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PostPosted: 04 Mar 2017, 13:17 
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Geek wrote:
M. Gregg wrote:
I don't use wafer switches to switch signals, I use relays.


:thumbsup: :thumbsup: :thumbsup:

Omron G5V-2-H1 DC[x] are my go-to signal switchers :D


:D yes they work great.
Standard power relays fail after a while with high resistance oxides.
I plug them into IC sockets so I can change them easily.
I tested them with and without the sockets couldn't hear any difference so I use the IC sockets all the time.
The low profile sockets are so small they make no physical impact..NB I have never had a relay fail.

Regards
M. Gregg

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