[sdiy] Power Supply Question

[Scott Gravenhorst]

"Rude 66" <r.lekx at chello.nl> wrote:
>> Wow, what a relief from the analog better, no digital better, no vinyl
>> better, no CDs better...  I broke my delete key on that one.  Whew.  So
>thank
>> you for this,  a REAL SYNTH-DIY question!
>>
>
>(lifts imaginary glasses from eyes) it is I! Leclerc!
>
>it was me who originally asked ray this question. his synth asks for 2 9v
>batteries for power, but i wanted to power it from a wall wart of some sort.
>all the mentioned options are a bit over my budget, it's supposed to be a
>cheap fun synth after all..;-) but thanks for the options.. i was a little
>lost on what to do. 2 9 volt supplies? one 18 v supply? a splitter? etc.
>
>what about a compsomise? can i use one normal wall wart adapter and one 9v
>battery? if so, ray, what would be best to power what? would a dying battery
>cause any interesting side-effects like in circuit bending?
>
>r./

Hey, r./, I understand budget...  One of the things I do is collect wallwarts
from stuff I and other people toss in the trash.  Very often, little
appliances that use wallwarts break inside and the wallwart is just fine.  I
have a serious collection of all kinds of them.  I haven't ever bought one
that I can remember.  I think I have some 15 of them on a shelf waiting for
whatever project begs them.  The only money I spend on power supplies is the
regs, diodes and caps.

I believe that in _most_ cases, the positive supply demands are greater than
the negative.  In _my_ case, that may not be true because many of my VCOs
wind up being powered from ground and -V, along with wave shapers, etc., and
with my recent spate of CMOS linear amp stuff, it may be that my supplys'
demands are about equal.  YMMV.  If it were me...  I'd build a dual halfwave
thing from a single wallwart.  The 1/2 wallwart and 1/2 battery thing will
work, but batteries which are dying will not necessarily give you repeatable
results.  Better (IMHO) to use more straightforward techniques to do current
limiting and voltage droop stuff, then you can make it happen again and again
and again as you need (and with a knob!).  I mean, wouldn't it suck to have
to _find_ a suitably half dead battery for a performance?

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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