[sdiy] +-12V supply

[Roy J. Tellason]

On Saturday 15 January 2005 03:42 am, harrybissell wrote:
> If its a large audio producing system... it could be harmful or fatal
> to power amps, speakers etc.  Sounds really nasty in MY system.
> fixed now :^P
>
> H^) harry

Yes,  in power audio it's definitely something to worry about...

I have a Kustom amp,  and rewired the extra second input jack to be a direct 
power amp in,  bypassing the noisy preamp section in there.  Found out the 
hard way when I was messing with it that the input plug contains the (only!) 
ground reference for the input of the power amp,  and that when disconnected 
it puts +40 volts on to the speaker terminal.  :-(

That unit now has a speaker protection board added!

> "Roy J. Tellason" wrote:
> > On Friday 14 January 2005 09:45 pm, groovyshaman wrote:
> > > I am curious Harry - what is the advantage of a soft start mechanism? 
> > > Does this in some way help alleviate the initial heavy current outrush
> > > that occurs when turning on the power due to all of the decoupling caps
> > > on all of the modules in my system?
> > >
> > > I've noticed that from time to time when I power up the 800ma power
> > > one, one rail "goes flat" due to current limit circuitry I think - and
> > > I immediately shutdown when this occurs.  Hopefully this does not harm
> > > things.  (although I think I remember someone mentioning that running
> > > certain ICs with one dead rail for any length of time will kill the
> > > part..) I'm still running the supply below the rated output once things
> > > power up ok.  It's the initial current draw that's causing problems.
> > >
> > > George
> >
> > I've wondered about that,  operating some parts with one rail getting
> > there before the other or one possibly going away due to some system
> > fault.  I don't remember anything in any datasheets about this,  though.
> >
> > One of my projects from way back when was a "tracking regulator",  that
> > would match both rails to each other.  Used an MC1468 (?) chip,  I think.
> >
> > > ----- Original Message -----
> > > From: "harrybissell" <harrybissell at prodigy.net>
> > > To: "Ken Stone" <sasami at hotkey.net.au>
> > > Cc: <synth-diy at dropmix.xs4all.nl>
> > > Sent: Friday, January 14, 2005 11:41 PM
> > > Subject: Re: [sdiy] +-12V supply
> > >
> > > > I considered building a relay based "soft start" for my PowerOne
> > > > supply as "building my own power supply".  The only time I would
> > > > build my own is....
> > > >
> > > > 1) when I want cheap and dirty and don't care about performance
> > > >
> > > > 2) when it has to fit into a custom sized area
> > > >
> > > > 3) when I need an odd voltage not readily available
> > > >
> > > > H^) harry
> > >
> > > <snip>