PortaCom Adapter

Hey Everyone,

I work at a high school theater and the PortaCom headsets we have don't last what we would expect for a $220/ea. We typically get 2 years out of a headset before the mic starts having intermittent cutting in and out. I am dealing with teenagers and the are generally less then gentle with the gear (though we have 3 old headsets from the early 90's that just keep going!)

After looking at the pin out on the belt packs a few of us though of making an adapter: 4pin XLR to dual 1/8" female (one for audio, one for mic)

Our current thought process is to use a standard computer headset and for $20 each even if we have to replace them twice per year it's still cheaper then replacing actual portacoms every few years. (I picked up one of these to test: Sennheiser PC 21-II - Voip Headset - Internet Telephony, Skype - Noise Cancelling Microphone

While working on a proof of concept I ran into a little bit of a road block. I wired the ear piece first and it works great but while working on the mic I can't get it to work regardless of the configuration. I tested it by pluging it into a computer and all worked as expected. Just to appease myself I wired in an SM58 into the adapter and it worked perfectly.

Does anyone have any thoughts on this?

Thanks,
Joe
 
Most computer microphones are electret condensers. Most professional headets use dynamic microphones, and an S58 is also dynamic.
The main difference is that a condenser mic has some electronics inbuilt and so needs some power to make it work.
For most electrets, it's a bias voltage of around 5v, with a series current limiting resistor, and the PC sound card normally supplies this.

So you need to add this into the mix to make your headset work. There's a diagram on Wikipedia's page on Electret mics that might give you what you need: Electret microphone - Wikipedia, the free encyclopedia

You might also want to have a look at this old thread on the same sort of subject: Electret microphone for ClearCom system | ControlBooth
 
Agreed with Chris. Sounds like your headset's mic is looking for power that's not supplied by your beltpacks.
 
What comms beltpacks are you connecting to?
It's a long shot given the other things you'ev mentioned, but some of the modern beltpacks have a jumper selectable option to enable bias power from the beltpack...
 
Thanks guys, you were right - it needed DC bias power. I didn't think standard PC headsets used electret condenser mics. A quick trip to radio shack for a AA enclosure and a resister and all is well. The adapter works well but I have to find a way to make it smaller if I'm going to try to implement a few of them.
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If the kids are tearing up the headsets, you'll really have to make your adapter bulletproof. Which will be made more difficult by needing access to the batteries. Unfortunately the 1/8 inch jacks hardly qualify as rugged and dependable. Nice job making it work though!
 
FWIW, from two different directions;

My community access studio used Beyer DT-109s, and we got *stupid* amounts of life out of them.

And the Panasonic KX-TCA60 is the least expensive 2.5mm headset on the market. :)
 
You might want to find out why your headsets are failing. My bet is a wire breaks where the cable enters the XLR connector. A few minutes with a soldering iron might repair them.
 
If the kids are tearing up the headsets, you'll really have to make your adapter bulletproof. Which will be made more difficult by needing access to the batteries. Unfortunately the 1/8 inch jacks hardly qualify as rugged and dependable. Nice job making it work though!

Yeah I'm not confident this will be my actual solution - if just a small dummy adapter would have worked I could build it small and strong enough that it could take a beating. Once I realized how it had to be built it was more a matter of me just getting it to work because I was determined. I may build a few more of these and have them on hand as a back up.
 
FWIW, from two different directions;

My community access studio used Beyer DT-109s, and we got *stupid* amounts of life out of them.

And the Panasonic KX-TCA60 is the least expensive 2.5mm headset on the market. :)

Thank you, I'll look into seeing if the powers that control the purse strings can get me a pair of Beyers to try out. I have no problem spending the money as long as I get the value out of it.
 
You might want to find out why your headsets are failing. My bet is a wire breaks where the cable enters the XLR connector. A few minutes with a soldering iron might repair them.

Oh I know why they are failing... It's more of a 3 fold problem.
-The build quality isn't what it was 10 years ago (I have a few that still work to prove it.)
-My kids aren't as delicate with them as I would like (though they are getting better, the last 2 years I've had some great kids come in)
-We use them EVERYWHERE

I work at a High School where the theater and television programs are very closely interwoven and where applicable we use the same equipment so we can expand or swap out if need be. We have the same comms system for both places: channel A is the theater and channel B is the tv studio - that way we can communicate with one another if needed during a show. We only have so many headsets and the school doesn't want to spend the money to replace them all at once; we typically get 2-3 per year. In service at any given point we have enough comms equipment to run the theater (7), TV studio/control room (3), cameras (4) and our TV studios remote truck (3). should any break during the course of the year we have to take one from another area until the following year when we can budget for it.

As for repairs - we do replace connectors as they start to fail but when the mics start to fail that is when we usually end up stripping them for parts and tossing the caracas of a headset that remains.
 
Bite the bullet, and buy a spare. Or two. Or repair dead ones... they were trash anyway. Just don't /admit/ it. :)

Sent from my SPH-L720
 
Oh I know why they are failing... It's more of a 3 fold problem.
-The build quality isn't what it was 10 years ago (I have a few that still work to prove it.)
-My kids aren't as delicate with them as I would like (though they are getting better, the last 2 years I've had some great kids come in)
-We use them EVERYWHERE

I work at a High School where the theater and television programs are very closely interwoven and where applicable we use the same equipment so we can expand or swap out if need be. We have the same comms system for both places: channel A is the theater and channel B is the tv studio - that way we can communicate with one another if needed during a show. We only have so many headsets and the school doesn't want to spend the money to replace them all at once; we typically get 2-3 per year. In service at any given point we have enough comms equipment to run the theater (7), TV studio/control room (3), cameras (4) and our TV studios remote truck (3). should any break during the course of the year we have to take one from another area until the following year when we can budget for it.

As for repairs - we do replace connectors as they start to fail but when the mics start to fail that is when we usually end up stripping them for parts and tossing the caracas of a headset that remains.
Hey Joe,

I am looking for some parts for these headsets...If you are simply tossing the carcasses, please contact me ([email protected]). I might be able to use some of those discarded parts.
 
FWIW, from two different directions;

My community access studio used Beyer DT-109s, and we got *stupid* amounts of life out of them.

And the Panasonic KX-TCA60 is the least expensive 2.5mm headset on the market. :)

Jay,

I forgot all about this post until someone responded to it today! I just wanted to say THANK YOU. In my original post I mentioned 3 really old headsets that just keep going but they didn't have any marking on them so I had no idea what they were. You had suggested the Beyer DT-109, I looked them up and that was the headset! Since then I had the school purchase a few of them, while they cost a little bit more they are absolutely bullet proof.

Thanks again for the suggestion,
Joe
 
It might be possible to use a button cell or one of those 6 volt 1/3 AAA size batteries in a XLR connector or barrel. Most analog com like Clear com or PI runs of 20-30volts, it is possible to tap into the com power supply from the belt pack, but you would probably need to use a regulator to drop the voltage; most consumer headset electret mics don't run over 10v or so.

Basically you y-cable the 3 pin com line to still allow pass through to the next beltpack, and you then have to y-cable that into your 4-pin to tap into the power for your mic. Kind of messy. Google it, there should be a couple example circuits that people have used, but not really a clean solution.
 

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