[sdiy] keeping signals seperate..avoiding noise

Seb Francis seb at burnit.co.uk
Sat Nov 15 20:37:21 CET 2008


Justin Owen wrote:
> -----Original Message-----
> From: Laurie Biddulph [elby_designs at ozemail.com.au]
> Subject: Re: [sdiy] keeping signals seperate..avoiding noise
>
>   
>> As a matter of good construction, the power supplies for each board should be run direct to the main power supply in
>> what is sometimes referred to as `star' fashion. Daisy-chaining from one board to the next will allow noise induced on
>> to the lines from one board to be radiated to the others.
>>     
>
> Would the same apply to pots wired as volume controls - i.e. where one pin goes to Earth/Ground?
>   

No, it only applies when you are drawing current, especially current 
spikes, as then the resistance and inductance of the power line causes 
the voltage along it to fluctuate.  It different circuits share the same 
power line, the spikes will then couple between them.

For panel controls it may be better not to use star-earth if they are 
also earth-connected through a metal panel as you could get ground loops 
(=hum).  When using shielded cable it is normal to connect the earth at 
1 end only to avoid ground loops.

Seb






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