SV: Re: SV: Re: SV: RE: [sdiy] Multiple Voltage Power Supply / design problem!

[Seb Francis]

karl dalen wrote:
> --- Seb Francis <seb at burnit.co.uk> skrev:
>
>   
>> If you wanted to do things the linear way then just a normal 15V AC 
>> wallwart will give you +/-15V DC.
>>     
>
> Yes and no, that will give half wave rectification and the regulators
> will go dearly hot even with large reservoar capps.(depends on current
> offcourse).
>  

I've never had a problem doing this.  Just need to have smoothing caps 
double the size compared to full wave rectification.  Then the voltage 
drop per cycle is the same, and hence the voltage margin between 
transformer output and regulator threshold can also be the same 
(resulting in the same heat dissipation).

At least, this seems to make sense in theory.  I've never taken the time 
to actually test it scientifically - but in practise it works.

Seb