# Issues with connecting an electret microphone to a recorder's phantom power.

#### zushi000

May 19, 2024
3
Hello everyone, here's the situation. I recently bought a handheld recorder (Zoom H6 Essential). It has an XLR input with 48V phantom power. I purchased some PUI AOM-5024L-HD-R electret microphones to record ambient sounds. Based on some forum posts(https://www.instructables.com/The-Sound-Sleuthers/), I used a circuit called "Simple P48" to connect the microphones to the XLR input. It works well, and the sound is clear. However, I have some questions and hope someone can help me understand.

When I plug an empty XLR connector into the recorder and turn on the phantom power, I measure a voltage of 48.2V between pins 1 and 3 using a digital multimeter. When I plug in the Simple P48, the voltage between pins 1 and 3 drops to 44V. Why is there a voltage drop? Is it because the internal 6.8k ohm resistors of the phantom power are forming a voltage divider with R1 and the electret microphone? Even more puzzling, when I measure the voltage across the two pins of the electret microphone, it continuously rises from about 6V to 13V.

Why is this voltage continuously changing, and why can the microphone still function normally without being damaged even though the 13V voltage seems to exceed the maximum operating voltage of 10V for the electret microphone?

#### Attachments

• QQ截图20240519100113.png
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• QQ截图20240519100157.png
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#### Delta Prime

Jul 29, 2020
2,261
When I plug in the Simple P48, the voltage between pins 1 and 3 drops to 44V. Why is there a voltage drop?
What about the voltage on the hot side pins one and two both cold and hot have a 6.8 k resistors. E =IR there is your voltage drop.
Why is there a voltage drop? Is it because the internal 6.8k ohm resistors of the phantom power are forming a voltage divider with R1 and the electret microphone?

#### Attachments

• PSW_Mics_Chp2_WP.pdf
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• sboa320a.pdf
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#### zushi000

May 19, 2024
3
What about the voltage on the hot side pins one and two both cold and hot have a 6.8 k resistors. E =IR there is your voltage drop.

Thanks for your PDF.I think I've found the reason why the voltage at both wires of the microphone keeps rising. I'm using a digital multimeter, and digital multimeters have high impedance. This is the answer that ChatGPT gave me. I think it makes sense, and I'll try using an old-fashioned mechanical voltmeter tomorrow.

#### bertus

Moderator
Nov 8, 2019
3,407
Hello,

Have a look at the following page:
It will tell you how to power your electret microphone.

Bertus

#### zushi000

May 19, 2024
3
Hello,

Have a look at the following page:
It will tell you how to power your electret microphone.

Bertus
I have read this article before.thanks,l just want to confirm the exact bias voltage.But I can't measure it with a digital multimeter.

#### Delta Prime

Jul 29, 2020
2,261
Respectfully Yes you can measure it with a digital multimeter. you just don't know what you're looking at or what you're measuring.
Chat GPT? That is the dark side... The revolution has begun. The schematics provided in the PDFs especially Texas instruments gives a "Prime"example but if you cannot read schematics that's okay too...
Do you like movies?

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