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Request for help adding a microphone to a headphone amp

catalogguy

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My mother is hard if hearing and particularly difficult for her is getting a clear understanding of voices on TV. She us quite pleased that I set her up with a bluetooth transmitter, bluetooth receiver/DAC/amp combo device, and a set of Koss headphones.

Separately, my sister bought her a small portable listening device that my mom seems to prefer at times over using her hearing aids. It uses cheap earphones and a little microphone that can be unplugged. My mom recognizes that it is a cheap device and wonders if she could use the other amp in the same way for better performance.

The portable amp I bought her is an xDuoo xp-2 pro (it can play tv audio quite loud). When I plugged the mic into the xDuoo analog input, the xDuoo did not produce any sound, even at full volume.

Is there a way to make this work? Is another microphone needed? Or is there something about using the analog input that will not work with a microphone?

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Dunring

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I see you have a blue LED (for bluetooth), doesn't the input button cycle it to green for aux in?
 

restorer-john

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THe microphone is an electret condenser and needs a suitable preamplifier to bring it up to line level. They also require a bias voltage (for the tiny internal FET) which is not present on the line input to your H/P amp.

With a 5V supply, this would work into your H/P amp and also has the option of AGC. Uses a MAX-9814 mic preamp.

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https://www.ebay.com.au/itm/353168187448?hash=item523a76e038:g:3GsAAOSwjNxc7Kpy
 
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catalogguy

catalogguy

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THe microphone is an electret condenser and needs a suitable preamplifier to bring it up to line level. They also require a bias voltage (for the tiny internal FET) which is not present on the line input to your H/P amp. With a 5V supply, this would work into your H/P amp and also has the option of AGC. Uses a MAX-9814 mic preamp.
https://www.ebay.com.au/itm/353168187448?hash=item523a76e038:g:3GsAAOSwjNxc7Kpy

Thanks for this information. Based on the requirement, I will need to find something self-contained and at least somewhat durable (can be dropped into a purse and pulled out and remain in tact). If it needs power, then it will need its own source. Perhaps something like a small bluetooth microphone would be a good approach. A quick google search shows most of them are way too bulky, but perhaps something more like this "lapel" style... https://www.amazon.com/Lewinner-Wir...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
 
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catalogguy

catalogguy

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I see you have a blue LED (for bluetooth), doesn't the input button cycle it to green for aux in?

Yes, exactly what I was thinking. Unfortunately, simply plugging the mic into the analog input and setting the amp to use the analog input did not work. The amp has a built-in mic, but it seems to have very limited functionality; from the manual: "Microphone: only supports phone call mode."
 
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catalogguy

catalogguy

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Last edited:

AnalogSteph

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You should at least be getting something like that, but it may very well be pretty quiet. Sensitivity of this mic is on the lower side for an electret at -45 dBV / Pa if I'm not mistaken. That's an output of 5.6 mV at 94 dB SPL. 94 dB is pretty loud, and 5.6 mV is not very much. Keep on looking for portable mic preamps with 3.5 mm in/out I guess. There's always adapters if you need to get the left channel onto both.
 
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