[sdiy] Power Suppy for Doepfer module

[Scott Gravenhorst]

steve jones <stevejones at hotpop.com> wrote:
>On Sat, 06 Aug 2005 13:25:50 +0100, you wrote:
>
>>Short answer: no, it's no suitable.
>>
>>A couple of reasons for you ..
>>(a) It's unregulated (hence the 34.1V reading with no load)
>>(b) You can't generate a split voltage from a single voltage using a 
>>potential divider because (apart from the fact that it wastes a lot of 
>>power) the 0V point will move about depending on the load on each power 
>>rail.  The lower the resistor values the less this will happen, but the 
>>more power you will burn (and with a 100mA PSU you don't have a lot to 
>>waste).

This may not apply to your circumstance, but if the application is not
terribly critical, the zero point can be stabilized with an opamp (within a
limited current range), but the waste current will be smaller since the
system is dyamic.  The resistors-only method is static and the only way to
get better stability is with smaller resistors (hence the current draw
problem).  I've done this with 9v batter supplies to make +/- 4.5V.

>thanks for the quick response - that makes perfect sense. Would there
>be any way to use this power supply or even a 9V DC power supply to
>produce +/- 12V? What about batteries? 
>
>
>>
>>It's pretty straightforward to build a small PSU, or you can buy one off 
>>the shelf quite cheap.  If you'd like more info about these 2 options 
>>just ask.
>>
>>Seb
>
>.. any links for an off the shelf supply?
>
>Thanks for the  advice,
>Steve
>
>>
>>steve jones wrote:
>>
>>>Hi,
>>>
>>>I have a A-136 Distortion / waveshaper module which I want to enclose
>>>as a single effect unit. It needs +/- 12v to +/-15v.   I have a spare
>>>Electro Harmonics  24v DC 100mA wall wart and was wondering if this
>>>could be used, and how?  (? using a pair of resistors in series across
>>>the + and - outputs of the wall wart, tapping the 0v between them?
>>>what size resistors?)
>>>
>>>However, when I measured the output voltage of the wall wart (when not
>>>connected to anything) it read 34.1 volts. Is this normal, or is it
>>>faulty?
>>>
>>>Thanks for any advice,
>>>Steve
>>>
>>>
>>>
>>>
>>>  
>>>
>
>
>

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