[sdiy] Why dual grounds?

[Stewart Pye]

Since many of the modular synth standard power supply connectors (MOTM, 
Oakley, Blacet etc) have two ground wires, is one of these used for a 
"clean" ground and the other "dirty ?

Regards,
Stewart.

Dave Manley wrote:
> The way I've understood it: current spikes can cause the local ground 
> reference to rise, since the ground connection isn't perfect and has 
> non-zero impedance.  If you isolate the circuitry that generates 
> current spikes (digital logic, LED drivers, 555 timers, etc) to the 
> dirty ground, then the current flowing through the dirty ground can't 
> affect the clean ground reference and couple switching noise into your 
> audio path.
>
> If you connect the two on the pcb and there is a poor connection back 
> to the power supply, then the ground at the pcb can get disturbed due 
> to current spikes on that board.  On the other hand if you have a 
> separate path for both grounds back to the power supply, then the 
> clean ground stays quiet.
>
> -Dave
>
> David Ingebretsen wrote:
>> Thanks Paul. I've been reading about ground loops, star grounding, 
>> and other
>> grounding concepts as I've been puzzling over this.
>>
>> David
>>
>> ~~ -----Original Message-----
>> ~~ From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-
>> ~~ bounces at dropmix.xs4all.nl] On Behalf Of Paul Perry
>> ~~ Sent: Tuesday, June 08, 2010 11:43 PM
>> ~~ To: synth-diy at dropmix.xs4all.nl
>> ~~ Subject: Re: [sdiy] Why dual grounds?
>> ~~ ~~ As close to the power supply as possible.
>> ~~ So there is as little 'ground' in common as possible.
>> ~~ ~~ Another thing to read about in grounding , is "star grounding".
>> ~~ Plenty of references on the net for this ;D
>> ~~ ~~ paul perry Melbourne Australia
>> ~~ ~~ ----- Original Message -----
>> ~~ From: "David Ingebretsen" > Won't these two grounds eventually 
>> have to be
>> ~~ connected together though? I
>> ~~ > guess that's my main question. I can layout the PCB with separate
>> ~~ grounds,
>> ~~ > I'm just baffled as to where/when these two grounds touch each 
>> other.
>> ~~ >
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>>   
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