Electret microphone for ClearCom system

[TheGuruat12]

Okay, so I am one of the many people who want to make a ClearCom headset out of a computer or cell-phone headset. I know that the electret microphone in the headset would have to be powered with separate circuitry, built out of a few RadioShack parts, but wonder: Would it be possible to use a variable resistor (in place of a static one) as a gain control for the mic?

 

[dramatech]

I did just what you are trying to do, on 10 production intercom packs that we use with our clearcom powersupply, and another 15 clearcom beltpacks. I used a variable resistor for a mic gain control, but I didn't provide access to adjust it with the case on. I adjusted each one before I closed the case. I also provided a seperate connector for the electret headset. I used the mini XLR that is used by Shure for their wireless mics. This way the large XLR can still be used with a dynamic mic headset and the smaller connector on the front can be used with the electret headset. It has been doing just fine for 2 years now.
The electret headsets are very inexpensive, and when our teenage followspot operators break the headset, we just cut the connector off and use it on another headset. I keep plenty on hand.

 

[jonliles]

Do you have schematics for your mod? i have a few Telex packs I would like to do that to.

 

[dramatech]

I didn't really use a schematic. I just used the theory and experimented until I had one working, and then did nine more.
If you are not in a real hurry, I will see if I can take one apart and create a schematic. We hare focusing for "Cheaper by the Dozen", for the next few days. I will try and get to it as fast as I can.

Tom Johnson
Florida's Most Honored Community Theatre
[email protected]

 

[jonliles]

That would be great!

 

[tomed101]

This is probably not the case for you, but if you happen to be using the current generation of Clear Com beltpacks (the 6xx series) they actually have an electret amp circuit built in. They even have a 2.5mm mini jack in addition to the 4 pin XLR, and both can be individually switched so you can still use a dynamic headset on the XLR with an electret on the mini.

 

[TheGuruat12]

No, unfortunately, all of the beltpacks on our system are Production Intercom's BP1 or BP1SL.

 

[Cburg]

I didn't really use a schematic. I just used the theory and experimented until I had one working, and then did nine more.
If you are not in a real hurry, I will see if I can take one apart and create a schematic. We hare focusing for "Cheaper by the Dozen", for the next few days. I will try and get to it as fast as I can.

Tom Johnson
Florida's Most Honored Community Theatre
[email protected]

I am searching for the same information on headsets and I was wondering if you were able to put a schematic together. I sure would be glad to see a copy if you did.

Thanks
Cburg

 

[themuzicman]

I am searching for the same information on headsets and I was wondering if you were able to put a schematic together. I sure would be glad to see a copy if you did.

Thanks
Cburg

If you google "basic electret mic preamp" you'll get a ton of options, from super fancy to super simple. Last time I built a bunch it was a basic circuit like this -- I used a 9V battery and adjusted the resistor until the gain suited my system - though a variable resistor would be much better if you didn't know what headsets you'd be using. I may still have one or two on my workbench and could tell you what parts I used -- they were built to work with Motorola's security style earpieces.