DIY phantom power unit

[Doink]

I've been looking at building a phantom power supply. Is it as simple as taking a wall wart, chopping the end off, and connecting the + and - leads to the + and - leads of the cable going to the mic?

[The Green Hornet]

Yo Doink:

If and when you do this chopping and taping, make sure you're not standing in water when you grab the mic.


Green Hornet

[Harvey Gerst]

Originally posted by Doink
I've been looking at building a phantom power supply. Is it as simple as taking a wall wart, chopping the end off, and connecting the + and - leads to the + and - leads of the cable going to the mic?

No, it's not that simple.

First of all, you hafta find a wall wart that'll put out 48 volts of clean DC. then you hafta limit the current output to about 10ma by using a pair of closely matched 6.8k resistors (connected to the 48V DC "+" lead) and feed that (coming from the those 2 resistors) to the two signal leads of the mic (pins 2 and 3). Finally, you'll connect the "-" lead of the supply to ground (pin 1).

Then, you'll need a couple of 10mfd blocking capacitors in series with pins 2 and 3 (between where you added phantom power and the mixer) to prevent the DC signal from hitting the mic preamp or mixer. Some mixers already have those capacitors in place.