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I have a microphone, which is phantom powered. Now that microphone uses an XLR interface, which connects to a small device, that device connects to PC using USB 2.0 interface. Microphone capture and whatever has to do with microphone stuff works just fine.

But now the confusion is that many audio professionals use external hardware audio mixers (not like PC devices, shown as above picture), and they claim that a general PC can not do phantom power.

Why not? If the XLR microphone connects to a device, and that device connects to USB, can the PC operating system not send phantom power the same way?

If it's true, does that mean Linux or Windows or Unix what-ever OS it is, can't do Phantom Power and you need a different architecture for supplying Phantom power?

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up vote 6 down vote accepted

Your operating system does not have anything to do with that.

What counts is what your interface can do. The thing you plug your microphone into. Where this interface gets its power from is not important here. Maybe it's something like this:

Computer → USB power → Audio Interface → Phantom Power → Microphone

But it could also be like this:

Computer → USB connection → Audio Interface → Phantom Power → Microphone
             External Power Supply

The USB interface will supply the phantom power on its own. The OS doesn't know about this and doesn't need to.

Generally, if a USB audio interface has an XLR port, then chances are it supports phantom power, which is usually selectable with a small switch on the interface itself. I have never seen audio interfaces that let you turn on phantom power via their software, because phantom power being turned on or off is something that essentially does not matter at the software stage.

You really only need phantom power to operate condenser microphones – and most dynamic microphones (which don't need 48V) will operate just fine even with phantom power turned on (although I wouldn't recommend to let them run on it all the time).

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Well, 48v power on/off button i have in my XLR to USB device. Using the linux system or windows system i can capture audio just fine. Difference between phantom on and off is that when its on i have lot of sounds getting captured, when its off, its suiteable to use headphone. But my goal is to know phantom power is doable using USB driver signaling through the hardware where XLR is connected. Then it means, using software i can develop an application too, what is now in hardware level available. – YumYumYum Jun 25 '12 at 10:14
If there's a hardware switch for phantom power on your interface, then you can't just turn it off via USB signaling. As I said, I've never seen an audio interface that would let you toggle phantom power via software. It's always just a hardware switch in the pre-amp that comes after the XLR connection, and it's easier to manufacture this way. – slhck Jun 25 '12 at 10:16
Hmm, which means, developing this in a software is not recommended . Its the XLR to device straight then its doable. – YumYumYum Jun 25 '12 at 10:19
It's not a question of whether it's recommended. It depends on what hardware capabilities there are. If there's a hardware switch, you can't override it in software. – slhck Jun 25 '12 at 11:09

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