Make a Bluetooth Mono Headset/Mic on the cheap

Picture of Make a Bluetooth Mono Headset/Mic on the cheap
This instructable will show how to make a standard bluetooth headset act as a wireless mono earpiece, using sound from any 1/8" (3.5mm) stereo headphone jack. The microphone can also be used for skype or online gaming for consoles or PC. This instructable may also be useful for those who listen to streaming audio, podcasted radio shows, or listen to audiobooks from their mp3 players. The applications for this are pretty broad, and the price is less than $20.00 if you already own a bluetooth headset.
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Step 1: External Bluetooth Adapter

Picture of External Bluetooth Adapter
Back in the old days (late '90's-early 2000's), not all phones came with Bluetooth built in. This prompted companies such as Cardo to build external bluetooth adapters such as the BTA II. There are others available, but I got one of these for $.99 (used) on eBay. These can be repurposed with a little soldering to send an audio signal to any bluetooth headset, and deliver an audio signal back from the microphone if desired.

First, obtain your BTA II. Got it? Cool. Now use your thumbnail to pop the cover off. You'll see a battery, a circuit board, and the coiled wire that connects to your cell phone. Three wires connect the wire to the circuit board, on mine they were colored white, red and black. The white is +microphone, the red is +speaker, and the black is the common ground. De-solder these wires after carefully noting their orientation.

Step 2: Find an old set of headphones

Picture of Find an old set of headphones
You'll need an old set of headphones (make sure the plug is in good shape first) or a 3-conductor lead with a 1/8" headphone plug at the end. Cut the headphone cable to your desired length and strip the outer sheathing, then the inner 3 wires. The colors of the inner wires should be something like, white red and black, or white red and uninsulated. To save yourself some headache in the next step, you may want to twist and tin the exposed wire.
BudBump2 years ago
I checked EBAY for a BTA II and found two, but one was priced at $25. and the other one was $35. This places the price as too high for a Saturday afternoon project... that may or may not work when its done. I need something to use in class so I can hear the lecture and maybe record it too. This is more than a little science project diversion for me. I am hearing handicapped and am trying to find a tool that will not claw a hole in my wallet. Otherwise, my effort to bootstrap my work skills to a level sufficient to pay for my meds is nothing but toast. Thanks.
phithosd4 years ago
I was wondering if u could use an 1/8" to 1/4" adapter instead of opening it and soldering
Yes, but the adapter must be stereo to stereo. A mono adapter will not work.
dane244 years ago
a very good idea but were can I find a external bluetooth adapter?
Demascus4 years ago
I found several on ebay and amazon as well, new ones but they are there. Any ideas on how to hack a blue tooth ear piece to blue tooth ear piece. Want to make a wireless intercom from one motorcycle helment to the other.
i just finished this project, it works out quite well, but sound quality i not perfect, i was wondering whether it was the adapter, or the headset? (after all, the headset only cost 5 dollars)
Probably headset. I have a headset that sounds almost 8bit, although i'm sure its 24bit sound. Not graet but works for what i need it for. Nothing. Sorry its a bit late
Yeah same here, mine worked for bout a year with my ipod til one of the buttons of the adapter got all messed up. Thanks though
Always worth a try. Thanks author for your work.
stuffman (author)  Lance Mt.4 years ago
I think the problem with your sound is because you're not using a high fidelity protocol but rather one that is predominantly used for phone calls. That's why I say it's good for audiobooks and podcasts, but not really for music.
Demascus4 years ago
So if I added a small mic to the white wire I would have a wireless mike to a blue tooth ear piece is that correct?
I built this and It worked. The White wire is the Microphone input, so i was able to use the Cardo Bluetooth adapter to go completely wireless. Now I have a completely wireless stereo headset. I also spliced in telephone interface onto the Mic and Audio feeds, now i can use my Bluetooth headset to take calls from my Proprietary phone card, instead of using a corded Plantronics headset. Not bad considering those operator type headsets will usually run you around $200.
where can you buy the bta ii adapter? like in general store not online
stuffman (author)  hacks4life226 years ago
When I put this instructable together, they were available on eBay for between 1 and 10 dollars (I got mine for $.75 or something, but it was used). Now, if you can find them, they're a bit more than that. I don't know that you'd be able to find them in any retail store any more, since all phones have BT built in now.
Can you also use the Jabra a210 Bluetooth adapter? I have two of them, and in taking one apart I noticed it has 4 wires from the connector to the circuit board. Any thoughts on using it? Also, would it be possible to simply plug it into my BT enabled phone with a headset jack and get it to pair to my BT headset for mono sound without modification?
stuffman (author)  innovator16 years ago
Sure, that's what the a210 is for, it's actually exactly the same as the cardo. I've since used the a210 for other projects. If you're only going to your phone which has a 2.5mm headset jack anyway, you wont need to modify anything. Thanks, Shawn
I got mine at RadioShack, but you can go to and they have a "Where to buy" link.
icedude0077 years ago
(removed by author or community request)
stuffman (author)  icedude0077 years ago
Open up the casing on the unit, and see if there is any screen printed descriptions on the circuit board. Mine said "SPK", "MIC" and "GND", or something like that. The cable coloring shouldn't matter, since you'll be getting rid of the original cable anyhow. Good Luck, Shawn
Aureliano7 years ago
I would like to implement the microphone. Do you think that it will work as good?
stuffman (author)  Aureliano7 years ago
Sure, it will work fine. Just make sure you share the common ground wire, then you'll have to figure out which wire should be for mic, and which should be for speaker. It's a really simple mod.
would this work for my cell phone? i have an mp3 player on it and its also bluetooth compatible. i would kill for a wireless headset for my phone.
stuffman (author)  shrimpcracka7 years ago
This will work for any device with a 1/8" stereo jack. If yours has a headphone jack you can adapt the cardo to work with it. If yours has a headSET jack, and the audio will play through a wired headset, then all you have to do is plug the cardo in and pair to a bt earpiece, no modifications required. Since your phone has mp3 capabilities, you may check if it's compatible with the Bluetooth A2DP profile. If it is, all you have to do is buy a wireless bluetooth headphone outfit like this and you'll be all set. Always more fun to hack stuff apart, though. :0)
Hawaii000007 years ago
Will this give the ipod touch i mic CAN. but I don't think that the touch has audio-IN jack (per se). If you look around the intarwebs however, there are schematics for the audio IN pins on the bottom jack... Just hook those up to the leads here, and you'd be all set.
Thanks that is so cool I will have to get on and try that. How do you pair the bluetooth headset with the dongle. Ethan
stuffman (author)  mindstormmaster17 years ago
Pairing is easy, I think you hold the power button down on the cardo unit until the LEDs do something, I'm not sure. Here's the link to the manual, though: LINK

Another cool thing about this unit is that it is completely functional while charging. Most BT devices will only work while on battery power. With this one you can charge while using it, then unplug it and take it with you. The limiting factor is definitely the BT headset.