simple mic preamp / high level detection

Hello..

Can you point me to a very simple mic preamp design?

I am currently designing a monitoring controller for a 3D-dome and had the idea to incorporate an automatic mute function that reacts to high levels from a measuring microphone hanging from the ceiling. (In case you're not standing near the CUT button).

What would you do to the signal after the preamp? I thought about rectifying it and feeding it to the analog comparator of a microcontroller. In the end I need a micro controller to communicate the high-SPL situation to the main controller.

12dbLow said:

Can you point me to a very simple mic preamp design?

Click to expand...

For what mic? That can make a huge difference. Since you already have a MCU, you may want to look at a MEMS capsule with digital output.

I am currently designing a monitoring controller for a 3D-dome and had the idea to incorporate an automatic mute function that reacts to high levels from a measuring microphone hanging from the ceiling. (In case you're not standing near the CUT button).

Click to expand...

What is the source of these "high levels"? The PA itself or the cries of agony of the spectators? 
If the goal is to avoid excessive SPL from the PA, there are standards for safety regulations that you would want to adhere to.

The good news is the mic preamp for detecting "loud" sounds does not need to be very quiet, so a cheap op amp will work.

As noted you will probably want some kind of weighting function (filtering).

There are commercial products to detect high SPL..

Many modern microprocessors have built in A/D so you can pad down the op amp output (cap coupled and level shifted) then feed it into the micro.

I have written a lot of code for micro based meters so not rocket science but for crude loud noise detector you might not even need a micro.

JR

The 3D dome consists of 35 speakers, so I would rather measure actual SPL than to monitor all the levels.

I was thinking about using a cheap Behringer omnidirectional electret "measuring" mic.

The controller system will be based on add-in eurocards, so the SPL meter can have it's own card and micro.

The pro's for feeding the signal directly to the micro: Flexibility to experiment with software afterwards.
Cons: Longer development time in software.

Can you point me to examples for schematics to process the signal in the analog domain?

I already came across this, which looks very interesting:
https://davidegironi.blogspot.com/2014/02/a-simple-sound-pressure-level-meter-spl.html#.W_cUphCNykA

And this very simple preamp (I would have to add phantom power or use a dynamic microphone)
http://sound.whsites.net/project122.htm

abbey road d enfer said:

you may want to look at a MEMS capsule with digital output.

Click to expand...

That's a very interesting idea, but I would like to hang the microphone from the ceiling, so I think a normal XRL type would be better.

> mute function that reacts to high levels from a ...microphone. . . . CUT button . . . .

https://en.wikipedia.org/wiki/The_Clapper