[sdiy] 24V PSU Question

[Don Tillman]

   > Date: Wed, 12 Nov 2003 19:40:01 -0500
   > From: prototek <prototek at optonline.net>
   > 
   > The preamp functions off of 24V but also needs 48V for phantom
   > power.  Since I have no "hands on" experience with psu's this
   > puzzles me. Is there a way to tap both voltages off of one
   > supply, or do I need two seperate supplies (24V and 48V
   > respectively)? Any methods for doing this would be greatly
   > appreciated.

As others have mentioned, 24 V will generally power most phantom
powered mics okay.

But if you want to do it right, follow the industry standards, and be
able to describe it as proper phantom powered mic input, a 48 V supply
is required.

A common implementation is to generate the 48 V with a tiny switching
power supply.  See the Rane schematics for examples.  (Rane is to be
commended for having so many schematics available online at their
website http://www.rane.com) I personally wouldn't do that; I don't
think it's a good idea to have switching noise anywhere near a mic
input.

If I were doing it, I would tap into the secondary tranformer winding
of the main power supply, build a voltage doubler and regulate that 
to 48 V.

  -- Don

-- 
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com