What's the best way to provide 48V phantom power for a portable battery operated microphone device. Obviously a dc-dc convertor of some sort. Let's assume the power supply is dc 9V.If I were doing it from scratch I would make an oscillator - step up the voltage then rectify.
Hardy
If you haven't checked the actual voltage requirements already, it would be worth doing. I have a phantom powered mike for which the rated voltage is
48v, but speced minimum is 9v. It works fine at 8v as well.
Try it at 9 volts. Most still work fine. I use a Behringer ECM8000 measurement mic at 9v, but the spec says 48v I believe they mean that to be a maximum.
Barry
I was thinking of one of those tiny class D speaker amps, wired as a wien bridge osc, with suitable lightbulb (fet stabilisation should obviously never be used for audio :-) into a little step up tranny and a rectifier. Might work quite nicely
Martin
What happens the day you need to use a microphone that requires most of the 48 Volts ?
Duh, it won't work.
That's not conceivable in my setup. The only decent mic I own, and use, is the ECM8000.
I once had a U87 connected to a phantom supply that was turned off accidentally during a performance. The sound quality didn't change noticably, but it just got quieter and quieter over several seconds as the supply voltage died. I had the faders on the desk up full to compensate before I realised what had happened.
It's kinda obvious when you consider how that sort of condensor mic works. The gain of the preamp remains roughly constant but the mic element itself has a gain that's proportional to the bias voltage.
Not all mics work that way though, e.g. an FM mic doesn't bias the mic element with the supply voltage.
Regards, Allan
just LTspicified a little P48 generator, simply to try out this
I've stuck a zip of it here
Martin
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