[sdiy] power supplies

[harrybissell]

I recommend NOT using an AC wallwart to make a bipolar power supply...
unless you can get one of about 30VCT (Center Tapped).  This would give
two 15V windings, rectified that would be about 22 volts... enough to have good
headroom in a FULL WAVE CENTER TAP power supply design.

Using an 18VAC transformer will force you to make a HALF WAVE rectifier
supply... it will need 2X the filter caps and have ripple at 60Hz (harder to
filter than
the 120Hz of the FWCT supply)

Half wave supplies are only appropriate for very low power levels... if you
don't need much you could 'get away' with using one, but its not the preferred
way to go.

H^) harry

gregory zifcak wrote:

> i found this one, which apparently takes 16 or 12vac:
> http://sound.westhost.com/project05.htm
> would starting with 18vac give me higher output amperage? i'm not sure what
> my circuit needs. if i use 18vac, should i still use the 7815 and 7915? are
> there any other components that would have to be changed?
> thanks,
> greg
>
> >From: "gregory zifcak" <zifcak at hotmail.com>
> >To: resfreq at hoohahrecords.com, synth-diy at dropmix.xs4all.nl
> >Subject: Re: [sdiy] power supplies
> >Date: Wed, 25 Feb 2004 11:25:36 -0800
> >
> >wow, perfect! can you point me in the direction of some info on how to
> >build that supply?
> >thanks a million,
> >greg
> >
> >
> >>From: Dave Magnuson <resfreq at hoohahrecords.com>
> >>To: "gregory zifcak" <zifcak at hotmail.com>, synth-diy at dropmix.xs4all.nl
> >>Subject: Re: [sdiy] power supplies
> >>Date: Wed, 25 Feb 2004 13:59:09 -0500
> >>
> >>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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