Power supply?

[Don Tillman]

   From: gstopp at fibermux.com
   Date: Tue, 19 Nov 96 09:35:46 PST

   Switching power supplies (like you find in PC's) can be used to power 
   analog audio equipment, no problem. 

Now hold on a second Gene, how can you say "no problem"?

  They may need some filtering on their DC outputs to reduce noise. 
That's a problem.

   Also they will radiate electromagnetic waves at high frequencies,
That's a problem.

   Switchers can be tempermental - some will shut off if a certain 
   minimum load is not present, 
That's a major problem.

   Almost all of them have all voltage regulation functions tracking
   the +5 output *only*, which means if you load down the +5 to close
   to it's current  limit, it will be working hard and the +12 and -12
   outputs will be around 14 volts each! Pretty sucky regulation. 
That's a problem.

   Also if something goes  wrong inside, they will appear to be dead
   to the world, 
And generally not repairable.  That's a problem.

And those other things you mentioned too. 

----------------

If you want to build *inexpensive* synth it is going to be small and
it won't be eating up dozens of amperes.  So a power supply designed
to provide dozens of amperes is clearly not the right thing.  Also,
the synth is probably going to be built incrementally, and in the
early stages will need a supply that's going to be especially
well-behaved running at a couple mA.

This is simply no place for a switcher.  (This is one of those
"horribly misguided restrictions" I was talking about.)  If the goal
is to have it inexpensive, you can get little +/-15v supplies for
something like $20.  Or less surplus.  Or find an appropriate
transformer and build the power supply yourself. 

  -- Don