Microphone Preamplifier


It was Christmas and gift time to offer something to kids. Asked a very specific microphone, have to be wireless and need to be connected to our equipment.

Checking Amazon and here i go, buy this one [insert link and photo].

After arrived i saw a 1/4" mono plug and think ok will by a converter to 3/4" mono plug that it's.

Wrong, microphones voltage is to small for Line In or Aux In.

Found that microphones have about 50mV, Line In needs Volts not millis :)

Then started my adventure of building a microphone preamplifier, starting some perforated board, add some ampop and it works fine.

I hope so, but i forget to add a reverse polarity protection to 9V battery and was about to explode.

Schematic (Autodesk Eagle):

Schematic Sheet 1/1

BOM list:

[add bom list if possible as a table]

PCB (Autodesk Eagle):

PCB generate using Autodesk Eagle preview

And using EagleUp.

EagleUp Export

[add image of exported eagleup]


PCB Bottom



PCB Bottom

PCB 3D Model


PCB Assembled


PCB Assembled


Hammond Box - 1551BK

Build & Assembled:

[add images and descriptions if possible]

Code & Testing:

[add code and testing procedures]

Resources & Related Links:

[add some useful resources, files, links and GitHub for example]

add hammond box.

add mouser bom list.

All resources, eagle files and other in GitHub, https://github.com/neuralbit/micpreamp.

All of this is only possible because there are excellent companies, like Adafruit and Sparkfun, that take time to bring this to us.

Please support them.

Please contact me if you have something to share.