Throat Microphones with Behringer UMC1820 -> do I need a preamp?

[SonicDriver]

Dear community,

I have quite a tricky question. I am using five Retevis EAL002 throat mics to pick up breathing sounds for a collective experience. As I am using the Behringer UMC1820 for my sound installation I have soldered mono jacks with 3.5mm to the throat mics so I can plug them into my interface. Unfortunately something seems to be off, the voice being picked up is very low and it also creates a very high and loud noise. Also pressing "inst" and not pressing "pad" does not help. I guess I am in need of a preamp. I have looked a l ittle bit into DI boxes, for example the "DBX DI4 active four-channel Direct Box with line mixer". But I guess it's not really what I am looking for. I have no experience and knowledge about these devices therefore I was wondering if someone here has some better suggestions for preamps/di boxes. Thank you so much!

Best,
SonicDriver

 

[MarcelvdG]

Educated guess: it looks to me like the microphone requires consumer-type plug in power (PIP) while the Behringer only has professional 48 V phantom power or no power at all.

https://www.amazon.com/Retevis-Flexible-Earpiece-Headset-Cellphone/dp/B01A5DR284

https://www.behringer.com/product.html?modelCode=P0B2J

 

[MarcelvdG]

You could try building something like this as an interface between a microphone that needs PIP and a microphone input with 48 V phantom supply. No guarantees, neither tried nor tested.

 

[weltersys]

I am using five Retevis EAL002 throat mics to pick up breathing sounds for a collective experience. As I am using the Behringer UMC1820 for my sound installation I have soldered mono jacks with 3.5mm to the throat mics so I can plug them into my interface. Unfortunately something seems to be off, the voice being picked up is very low and it also creates a very high and loud noise. Also pressing "inst" and not pressing "pad" does not help. I guess I am in need of a preamp.

It's possible you are using one of the headset speakers as a mic- the 4pin wiring can be tricky.
The Behringer UMC1820 has 75dB of pre-amp gain on the mic inputs, more than enough if the 3V-5V "Plug in Power" (PIP) is provided to the mic element.
The UMC1820 1/4" jack inputs are made for line level and probably won't have enough gain, and don't provide 48v phantom power or PIP.
The mic inputs do have 48V phantom power, way too much if the Retevis EAL002 matches the specifications of this similar looking mic, standard operating voltage is 3V, maximum voltage is 10v.

You could use Pin 1 (red/+5V) and Pin 4(Black/GND) of a USB cord to provide the PIP.

You will need to determine if the Retevis EAL002 is wired to the OMTP or CTIA/AHJ standard shown in the above diagram to know what pin is ground, verify the speaker to ground resistance of around 25 ohms.

The mic + output should be connected in series through a 47uF DC blocking capacitor to the XLR pin 2, ground through a 47uF to XLR pin 3 and 1.

 

[weltersys]

Using a single USB to provide the PIP would also require isolation between mics.