O.K.. here is the issue,

I am building a preamp for the bass player at church, and i am contemplating installing a ssm2142 balanced line driver chip to have an onboard DI

what i need to know it how can i get +/- 15v from the Phantom power supply running from the sound desk?

any help would be great

cheers
Blair

http://www.diystompboxes.com/sboxforum/viewtopic.php?t=23268

Use 15V transformer and 7815, 7915 voltage regulators.

actually i was hoping to use the +48v phantom power that is supplied along the mic cables running from the sound desk,

but thanks for that, i had looked at similar options for my outboard preamp/DI box

If you can manage it, you simply have the DI ground reference sitting at 24VDC relative to the incoming phantom supply. Then, you've effectvely got ±24VDC to play with.

But, if you're building a pre-amp, won't you be building a ± supply anyway?

Keep in mind that the current available from the mixer's phantom power will be pretty limited....IIRC there is 6k8 in series with each side of the balanced line.

I don't know exactly how to get +/-15V out of a +48V phantom supply, but I'd be interested in knowing how. Like Tubebass said, tho, the current is pretty low. But, anyway... here's some cookbook ideas that might be useful...

Here's a scheme for an active DI box (quite nice, btw) that runs on phantom power...
http://w1.316.telia.com/~u31617586/
Appears to feed the active circuitry with +24V. But, maybe you can adapt it to your needs.

Another way to drop, or kind of regulate phantom power, might be to use a zener diode like in these microphone circuits...
http://www.jdbsound.com/art/art520.html

~ Charlie