[sdiy] Wallwarts and ground?

[Dave Manley]

James R. Coplin wrote:
> Thanks all!  I got it now.
>
> James R. Coplin  
>
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Scott Gravenhorst
> Sent: Sunday, March 22, 2009 12:02 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] Wallwarts and ground?
>
> "James R. Coplin" <james at ticalun.net> wrote:
>   
>> I think I understand where I'm getting confused. A two wire 9v 
>> supply with a + and - polarity is actually just delivering +9v 
>> and ground, not + and - 9v. Is this correct? If so, why do they 
>> call it negative instead of ground? Seems confusing to me... 
>>     
One last clarification: the '-' lead on the supply is almost certainly 
not ground.  The typical wall wart has an AC step-down transformer that 
isolates the low voltage outputs from the high voltage AC inputs.  
There's a good introduction to wall warts, voltage regulation, and 
filtering here:

http://www.dxing.info/equipment/wall_warts_bryant.dx

-Dave