The Covid 19 Pandemic has given me reason to use various video and audio type conference applications in order to access training and social gatherings.
Although my Laptop Computer has these built in, I don’y actually use my laptop as a laptop. It sits up on end with the lid closed. Connected to it is a monitor a USB keyboard, Cordless USB mouse, and an Ethernet cable. It is a close to being a Tower as a laptop gets.
Until the first online meeting I had not even given it a second thought. I joined the meeting relying on the built in microphone. This microphone I had to virtually shout at for the gathering to be able to here me.
The group wanted to see each other and so I figured I would hook up a new unopened albeit several years old Web Camera that has a built in Microphone. That solved the video issue, but being mounted atop a large monitor several feet away, I still found I have to raise my voice to be heard clearly.
If I moved the Webcam closer to me the mic was fine, but then the video was too close in for me and I did not really have anywhere to mount it.
I ordered a couple of cheap vintage style microphones from “AliExpress”.
So while waiting for them to arrive I raided my old salvaged parts bin and set about rigging up an Electret microphone to the Dell Inspirations Headset port.
I do not have one of the TRRS plugs to test the voltages on the Dells socket. I did have a TRS one though as found on standard old style earphones. The output is only about 2 volts using that plug.
Looking around the internet I noted that a Bias resistor and a coupling capacitor are recommended. The resistance apparently between 1K and 22K Ohms. The Capacitor between 1uF and 22uF.
I was getting better results directly attaching the Electret without either of these components.
I tried all sorts of combinations and even tried paralleling a couple of Electrets. Nothing was much better then the Webcams Microphone when more then a few inches away.
My attempts at amplifying them proved useless using the 2V bias voltage available. I might build a little battery powered microphone amplifier at some point.
It occurred to me that I had a Microphone on a little Arduino board delivered recently. I hooked that up and the signal was much improved. At first I thought the on-board microchip was giving amplification. I sourced the datasheet to see if I could employ the same technique.
looking at the circuit diagram the analogue signal simply went through a 150R resistor!
One of the cheap microphones arrived. The signal was again not a lot better then the Webcam Microphone. However, I could now move the Microphone around the desk.
Opening the Vintage Style microphone which has a little switch to enable or disable it. I noted it had an Electret that looked very much like the one from the Arduino. I tried paralleling them but the best output was still from the Arduino’s Microphone Module.
I took a look and they had different part numbers. The Arduino Microphone “CZN-15E” a search suggests these specifications “Microphone 2 feet 50~60DB The sensitivity of 54 “.
The Vintage Style Microphone is just marked SG. These seem to come in various sensitivities . The nearest I fond on a search of AliExpress was this “6050 Microphone capacitance electret SG electret microphone 6050p/9767p pin 9767 microphone pickup”.
For now the two microphones have swapped laces. The higher sensitivity is now installed in the Vintage Style Microphone where it seems to work well. I will test it next time I have to do the video conference thing.
I might order a selection of Electrets from AliExpress to compare at a later date.