[sdiy] Curious powersupply/power distribution problem

[Scott Gravenhorst]

elektrodwarf at yahoo.se wrote:
>Hi list
>
>I have a problem, i'm making a stompbox that's being fed from a 
>regular 9V transformer, internally i'm dividing it up to +-4.5V 
>because i need a split powersupply. Now this is working 
>perfectly, until someone plugs in one of those transformers that 
>feed several stomps. At that point my ground and the other 
>circuits grounds are 4.5V apart, problematically enough it won't 
>work for me to (just) use opamps that can run from non-polar 
>voltages. 
>
>Now what i need to do is to make my circuit work with audio 
>signals that aren't referenced to my ground, but in fact my 
>-4.5V. I tried biasing each signal with +4.5V but that didn't 
>work, to the problem belongs that i need to be able to use both 
>AC and DC signals. 
>

You say that you are using a 9 volt transformer - but is suspect it's got a rectifier
in it and supplies 9vDC ?  If not, you can use halfwave rectifiers and create a true
bipolar supply.  That would cause your gound to be zero volts instead of -4.5.  If you
need regulation - will +/- 5 volts work?  If so, three terminal 5v regulators...


-- ScottG
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-- Scott Gravenhorst
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