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I want to be able to talk on the microphone of my Headset A and send that signal out to the earphones of my Headset B. Something similar to what I show you on the image below.

enter image description here

For that purpose, I bought the piece below, which I can place in between both (it requires some power) to achieve my goal.

https://www.aliexpress.com/i/32949115279.html

enter image description here

It actually works but there is some noise on the output signal that I can easily hear on the earphones of Headset B. For example, when the room is in silent and even not talking, I can hear that noise.

Then, I was thinking to build or configure some mic (pre)amplifier or something similar that let me achieve my goal.

(I have to say that I'm not an expert on this field)

I got the following 3 pieces on Amazon because they claim they reduce the noise or something like that but I don't know if they are exactly what I'm looking for and how to configure them.


Noyito - 12V High-fidelity Microphone Pickup Module Noise Reduction Microphone Amplifier Board High Sensitivity Kit

https://www.amazon.com/gp/product/B07CQBJDTZ

enter image description here


Acxico - AD828 - Stereo Dynamic Microphone Preamplifier Board Pickup Module DC 3.8V-15V MIC Preamp Module

https://www.amazon.com/gp/product/B081YRNRP6

enter image description here


Koobook SSM2167 - Microphone Preamplifier Board Preamp COMP Compression Module DC 3V-5V

https://www.amazon.com/gp/product/B07TWC2MQB

enter image description here


Could you please, let me know if I can use them to achieve my goal?

Or if you have in mind any other way to do that, could you please, let me know?

Thanks in advance!

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  • \$\begingroup\$ Site rules: Questions on the use of electronic devices are off-topic as this site is intended specifically for questions on electronics design. - this means boards you buy from vendors unless supported by a data sheet and accurate schematic. You need to provide links for data sheet and schematic and not links to where to purchase them as they are irrelevant. \$\endgroup\$ – Andy aka Oct 11 '20 at 7:27
  • \$\begingroup\$ @davidesp: What does the "noise" sound like? White noise (sea waves crashing or wind through trees.) Buzz. Hum. Continuous high pitched whine. Intermittent chirps. Something else. \$\endgroup\$ – JRE Oct 11 '20 at 8:35
  • \$\begingroup\$ If you already have "too much noise" a preamplifier can only turn it worst. \$\endgroup\$ – carloc Oct 11 '20 at 8:38
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You have not linked to any relevant datasheets.

One of the boards has part number SSM2167 so we can easily find its datasheet : where Page 3 reveals(!) voltage noise of 20nV/sqrt(Hz) ... fairly noisy, considering SSM made their name as specialists in high quality audio. I guess it's adequate for some specific purpose, probably in a noisy environment since it includes a compressor. It does work happily off just 3V.

Another uses the AD828 (I note in passing that SSM was bought by AD) which is billed as a VIDEO opamp, with a bandwidth up to 90 MHz! A curious choice for a microphone. Nevertheless its input noise voltage is just 10 nV/sqrt(Hz) ... a little better.

The third doesn't say, but the photo shows a NE5532, which is 5 nV/rtHz, and has been a staple of pro audio since the 1980s (along with its slightly quieter single channel brother, NE5534, as Graham recommends). It's the best of the bunch for your application, assuming the rest of the board is up to scratch, and you can afford to power it (at least +/-5V, +/-12V better).

As mic amps go it's still pretty noisy; I've used the 5534 preceded by a discrete transistor stage to get input referred noise well below 1 nV/sqrt(Hz), when dealing with studio condenser mics. But there's no need to go to such lengths with the electret capsule fitted to your headphones.

The above all assumes the "noise" is simple white noise. If it's something else, buzzing, hum, etc you need to find the cause and eliminate that instead, e.g. by electrostatic screening around your amplifier, and/or improving your power supply.

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For the application you have in mind, almost any reasonably low noise amplifier chip typically with voltage noise below ~ 5nV/sqrt(Hz) should do fine. That'll exclude the popular LM4558 and LM741 for example.

Really low noise microphone amplifiers such as those in studio sound mixing consoles are designed for use with professional balanced low-impedance (usually 150-200 ohm) microphones. They are somewhat specialised designs using discrete transistor differential front ends with voltage noise below 1nV/sqrt(Hz). Their typical low input impedance (~2kohms) may not ideally suit an inexpensive unbalanced electret condensor mike. A headset mike also doesn't need a balanced input.

Of those examples you list, one is based on an SSM2167 chip which approaches the performance of the designs mentioned above, but no information is given as to the specifications.

In truth, many op-amps will do well for your mic amp. The ubiquitous NE5534 would be perfect in non-inverting configuration which is quieter than inverting mode. https://www.ti.com/product/NE5534

The Noyito board uses the dual version of this chip, the NE5532, but includes an electret microphone capsule on it.

Be aware that an electret mike has some self-noise that's not thermal in origin as it includes a JFET buffer.

Since none of the modules you link to have any specs, it's hard to choose one that's better for you.

Maybe you would like to find some examples with specs ?

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  • \$\begingroup\$ CM noise (line hum) noise from PSU is common (pun not intended) use a balance and CM choke with cap shunt to suppress. Noise dependent on wiring and PSU for CM switcher modulation rejection that is is caused by your system. \$\endgroup\$ – Tony Stewart EE75 Oct 11 '20 at 9:54
  • \$\begingroup\$ Most JFET self-noise is also thermal in origin, from the channel resistance electronics.stackexchange.com/a/15376/142 \$\endgroup\$ – endolith Mar 23 at 21:05
  • \$\begingroup\$ There'll be the thermal noise, for sure, plus 'excess noise'. That stuff gets everywhere ! \$\endgroup\$ – Graham Stevenson Mar 26 at 2:14
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The original board in your post should not cause significant noise. I have used it as a heaphone driver and it works fine. I suspect your noise is not generated by the chip but by the power supply arrangement or poor signal screening

To sort the problem more information would be essential. What sort of Mics are they? Electret or Dynamic. The latter require higher gain and so more care in sheilding and power supply earthing. Describe the noise, Pure white noise or some other sound, buzzing, huming does it change when you speak?. Pure white noise is really the only noise that will be changed by using different opamps. Power the circuit off a battery. Still noisy? Touch the circuit ground lead. Does the noise change when you do this?

The SSM2167 makes a great circuit for this type of intercom application as when correctly configured will prevent overdrive distortion and gate any circuit noise when you cease speaking. That said looking at the board confguration it will like require component changes and I am not entirely sure that on its own it will drive headphones without further buffering.

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  • \$\begingroup\$ That board is a terrible mic preamp because the LM386 is designed as a speaker driver. It has high input noise that usually is masked by a line-level signal. With a mic-level signal it is very audible. \$\endgroup\$ – AnalogKid Nov 4 '20 at 15:55
  • \$\begingroup\$ You're quite correct. I thought the first board was the AD828 (which I later tested and is still moderatly noisy through decent phones). The LM386 is just about the worst choice of amp for this purpose. A very crude and noisy amplifier fit for very simple small-speaker driving in low-fi applications only. \$\endgroup\$ – Bivviboy Nov 8 '20 at 9:08

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