[sdiy] keeping signals seperate..avoiding noise

Simon Brouwer simon.oo.o at xs4all.nl
Sat Nov 15 22:57:49 CET 2008


Seb Francis schreef:
> 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.
IMO in synthesizer modules the ground of a module should never be 
connected to its metal panel. The panel should be isolated from the 
module. The panels should be grounded by connecting one point of the 
mounting rails to the star point.

-- 
Vriendelijke groet, 
Simon Brouwer. 

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