Phantom powered Balanced Microphone Amplifier

Started by Pitchfork, February 10, 2025, 09:51:39 AM

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Pitchfork

I would like to make an amplifier for a balanced microphone that is powered from the phantom power from a mixing desk. Because of the very low power available I anticipate it would use single rail op-amps like the TLE2022 or equivalent
Obviously the 48 volt phantom power would have to be reduced to around 9-15 volts
Has anyone ever designed such an amplifier, if so please could you share the schematic?

PRR

Quote from: Pitchfork on February 10, 2025, 09:51:39 AMpowered from the phantom power from a mixing desk.

The "phantom power from a mixing desk" comes out of a microphone amplifier. Why do you need an additional amplifier in front of that?

Quote from: Pitchfork on February 10, 2025, 09:51:39 AMHas anyone ever designed such an amplifier 

Yes.
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ElectricDruid

There's a ton of stuff out there about this:

https://www.ti.com/lit/ug/tidt235/tidt235.pdf?ts=1665151334296
https://www.ti.com/lit/an/sboa320a/sboa320a.pdf?ts=1739163861028
https://www.thatcorp.com/datashts/AES129_Designing_Mic_Preamps.pdf
https://www.diyaudio.com/community/threads/how-to-use-phantom-power.172839/

The power is supplied through 6K8 resistors, so any load reduces the voltage straight away - you won't have to reduce it yourself. And you will need to stay well under 10mA for your current draw.

My advice for this would be to not try and reinvent a somewhat-complicated wheel, but to look for one of many existing and tried-and-tested designs. Phantom power has been around for mics since 1966, and for telephones since 1919, so it's not new tech!


PRR

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