XLR phantom power...

[one_true_leroy]

anyone here have expereience with building/schematics for XLR phantom power. I've got a digital 8-track with XLR, but no phantom power. I've got some electronics skills, and would like to build a supply, but I can't find the info for what I would need. Specific questions... since it is just juicing the signal, does there need to be any consideration of in/out impedence? How filtered must the supply be? My mic has a range given (i think 35-52V?)... is there an optimal in this range, or just anywhere will do? Thanks, all...leroy

[Gold Metal Flake]

1. Some stuff...

First, the voltage is applied to the pins through a couple of 4.7K or 5.6K resistors, which is far above the mic's impedance of around 200 ohms, so in this way impedance is not a problem. You will have to add a couple of 50 volt caps in series between the connector and the preamp to block the voltage. 50 microfarads should work well. Nice film caps.

The voltage should be between 42 and 48 volts.

It should be well filtered. Hum sucks. But a decent power supply can be made quieter with a pi filter or two. cap resistor cap.

Check the preamp schematic. Note where they inject the voltage (39 volts here) and see that they use 6.8k resistors. Also note the local filtration. (Remove the space before the .gif to view the image)

http://www.paia.com/phantsch .gif

Some companies make inline 48 volt injectors.

http://www.paia.com/ might have one.

[one_true_leroy]

2. thanks for your advice...

I looked at the schematic for the pre-amp... the only thing I don't understand is why the circuit ends in +out and -out instead of XLR. Is that for people w/o xlr jacks on their amps (and why +/-?)? I think I'll build from that schematic, though, and just go to an XLR. Many thanks again!!

[Gold Metal Flake]

3. Yes, you can sub an XLR or TRS 1/4" or anything.

They show two TS 1/4". I dunno why. Patch bay, maybe. But, you get it, so it don't matter none.

Post again with the results. :hi:

[BlueEyedSon]

4. Get a mic preamp w/phantom. Probably a bunch used/cheap on eBay

[Lights_Out]

5. I got what you need

Peavey makes an entire interface for mixers without phantom power. It's called the CT2 or something. It's a small box with two mic inputs and two mic outs that you put next to your mixer or recorder to give your condensors power.

[Lights_Out]

6. Correction

It's called the PS 2, not CT 2