[sdiy] power supplies

[Dave Magnuson]

At 10:46 AM 2/25/04 -0800, gregory zifcak wrote:
>
>hi all,
>i have a tama techstar that runs on +/- 15v. i am only using one of the 
>modules and trying to figure out how to recase it into something smaller 
>than the 10"x16" case it's currently in. my problem is, the power supply is 
>huge. i would love to be able to use a wall wart instead. how would i go 
>about converting unipolar (terminology?) dc to bipolar? would i need to 
>start with +30 volts dc in order to convert to +/-15? 

You could use an 18VAC wall wart and build a small bipolar regulated
supply.  You should easily be able to squeeze that circuit into a 4" x 4" x
1.5" space without much effort. (You could get it even smaller with careful
selection of heat sink size and component layout).  Would that be small
enough?

alternatively, does 
>anyone know if there's such a thing as a bipolar wall wart?

Yes, and that's an option.  Problem is that good (well regulated /
filtered)  bipolar wallwarts are a bit hard to find, and they're usually
pretty expensive.  But this would save the space of having to add the
regulators that I mention above.


 lastly, i am not 
>using any of the - volt functions of the synth parameters (- env, etc), does 
>this mean i might be able to run just +15v? i wouldn't just disconnect (or 
>ground) the board negative would i?

I've never seen the schematics, but I'm pretty sure this won't work.  The
negative rail probably connects to all of the opamps, etc.

Dave



Resonant Frequency:
resfreq at hoohahrecords.com
http://www.hoohahrecords.com/resfreq/index.html
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