Electret microphone hobby project

Thread Starter

Marz3

Joined May 22, 2021
5
I have background in programming and im new to electronics so pardon my knowledge, basicaly i have ordered bunch of op amps and electret microphone, i want to use it as my zoom microphone.

Parts that i have:
6x electret microphone
4x LM358L
1x TL071CDR
1x LM324SNG
all kind of resistors and capacitors..
a shielded stereo cable, thought it could be usefull.

First of all whatsup with this two microphone connected circuit design, I have seen some schematics, seems like lm358 is a good choice but some people are saying it generates too much noise, some people are suggesting tl071, here are some schematics i have found, what should i do, also i have read its possible to connect microphones in paralel or series for better pickup.
 

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Thread Starter

Marz3

Joined May 22, 2021
5
I also have a tpa board that i can harness some parts from if it could be usefull.
 
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Audioguru again

Joined Oct 21, 2019
3,174
LM358 dual and LM324 quad opamps are not used for audio because they produce horrible crossover distortion and hissss noise.
The TL071 was designed years ago to be a low noise and low distortion audio opamp, I have used tens of thousands of them in my audio engineering career. Better audio opamps are available today.

Electret mics do not work when in series or in parallel.
 

Thread Starter

Marz3

Joined May 22, 2021
5
LM358 dual and LM324 quad opamps are not used for audio because they produce horrible crossover distortion and hissss noise.
The TL071 was designed years ago to be a low noise and low distortion audio opamp, I have used tens of thousands of them in my audio engineering career. Better audio opamps are available today.

Electret mics do not work when in series or in parallel.
thank you very much so i will be using tl071 what would your better component suggestions, also about connecting elecret mics in paralel:

"

I am a technician at a boutique mic company. I like to build electret mics in my spare time.

You can increase sensitivity, gain, and signal to noise ratio by running multiple electrets in PARALLEL-not series. This works because:

1) each capsule has an onboard JFET. When combining noise from multiple FETs, some of it cancels. Two amps= -3dB, four amps= -6dB of noise reduction [see Small Signal Audio Design by Douglas Self, Routledge 2010].
2) Multiple elements will have lower output impedance, which can mean less noisy makeup gain down the line.
3) More diaphragm area means more sensitivity, which makes sense. It also means less self noise, for reasons that I don't really understand - but that's the principle behind the $3500 Audio Technica AT5047 (FOUR diaphragms!).

If you end up with a signal that is too hot and distorts the next stage, put a 10ohm resistor on the audio output of each capsule before wiring them in parallel. This averages rather than sums the outputs.

"
i have quoted this from :"https://electronics.stackexchange.c...multiple-electret-microphones-for-better-gain"
 

Audioguru again

Joined Oct 21, 2019
3,174
Numerous microphones pickup background noises and produce a directional sound beam due to phaser cancellation.
Your LM358 circuit has the electret microphones missing a bias voltage.
 

LowQCab

Joined Nov 6, 2012
517
There are several good suggestions that have been made here.
But the hands-down most-important factor is Room-Noise / Room-Reverberations.

If the Microphone is more than about ~6-inches away from your mouth,
the Room-Noise will be virtually equal in level to your Voice.
This starts to lessen Speech-Intelligibility, (clarity), very fast, the further you get from the Mic.

I would recommend using a set of Ear-Phones with a built-in "Boom-Mic"
that can be positioned within a few inches of your mouth.
The Mic being this close to your mouth makes possible the use of
Noise-Canceling Microphone-Construction, which can reduce
Room-Noise to inaudible levels.

Watch a bunch of YouTube Videos and compare the
sound quality vs the type and location of the Mic being used.

The Mic used in your Cell-Phone or Lap-Top is actually a pretty high-fidelity Mic,
but it sounds like crap because it is too far away from your mouth when
you are concentrating on getting your face on Camera.

AND, IT IS AN "OMNI-DIRECTIONAL" MIC.

Directional-Mics which are suitable for Professional-Productions,
are very tricky to build, and are seldom "perfect",
therefore, they are usually quite expensive,
and are "debated about", or "valued", very much like Musical-Instruments,
which is basically what they are,
with each design having its own "Character".

Some Mics are designed to be used "up-close",
and some are designed to be used at a
generally specified distance from the Sound source.

There are readily available "Noise-Canceling" Electret-Mics,
but they will only work "up-close" to the Element.
Standard design Electret-Mics are "Omni-Directional",
and will pick-up sounds from ANY direction.
This is strictly a Mechanical-Design-Problem, which applies to ALL Microphones.

If you need Maximum-Speech-Intelligibility in a noisy environment ...........
You might get some ideas from this DIY Speech-Processor Schematic,
it was designed to be a Motorcycle-Helmet-Intercom.
HeadPhone Amp Flat .png
 

Audioguru again

Joined Oct 21, 2019
3,174
TV stations used to play the "hide the mic" game which resulted in the mic hidden under a sweater or maybe in the next room giving horrible muffled sounds.
Now with Covid-19, people on TV are talking are at home with the mic hidden far away from them resulting in plenty of echoes sounding like they are in a washroom.
I agree that a mic should be close to and in front of a person's mouth.
 
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Thread Starter

Marz3

Joined May 22, 2021
5
I had a over the head headphone with a microphone built in, eventually it's cable died out, i had a stereo cable lying around so i have removed the microphone and currently using it with a good quality shielded cable, the microphone will be staying around 15 inch away from my face, im thinking about using the schematic sghioto shared, i have ordered multiple microphones so i want to test multiple possibilities, also i will be sharing end result audio files here, also thank you very much LowQCab, everything you said makes perfect sense.
 

BobaMosfet

Joined Jul 1, 2009
1,768
I have background in programming and im new to electronics so pardon my knowledge, basicaly i have ordered bunch of op amps and electret microphone, i want to use it as my zoom microphone.

Parts that i have:
6x electret microphone
4x LM358L
1x TL071CDR
1x LM324SNG
all kind of resistors and capacitors..
a shielded stereo cable, thought it could be usefull.

First of all whatsup with this two microphone connected circuit design, I have seen some schematics, seems like lm358 is a good choice but some people are saying it generates too much noise, some people are suggesting tl071, here are some schematics i have found, what should i do, also i have read its possible to connect microphones in paralel or series for better pickup.
Title: Understanding Basic Electronics, 1st Ed.
Publisher: The American Radio Relay League
ISBN: 0-87259-398-3
 

Thread Starter

Marz3

Joined May 22, 2021
5
I have finished the project, its much better than i have expected;
Now i can talk around 18 inch away from microphone and its very clear to be used as a voice microphone, before this card it was around 3-4 inch.

This was my first soldering project so i made some mistakes about design, today i have designed it in a program and now its much easier to solder it, i will share that file too.

First one i have soldered according to @sghioto schematic;
IMG_20210524_214329.jpg

Doing this took around 3 hours of my time, turns out there is a magical tool that can be used for pcb design... first one works perfectly but it looks very ugly, after moving the design to a pcb design program i have made another one for a friend;
IMG_20210526_171345.jpg

If you are new to electronics like me maybe you can use pcb design to make things easier here it is;
oshwlab project link
 
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