Bluetooth stereo hookup
For a long time I’ve had a pair of Bluetooth headphones (Insignia NS-BTHDP). This was one of my favorite gadgets – very comfortable, good sound quality, good battery life. I listen to music almost constantly when working, so these saw practically daily use for two years. Then one of the speakers started popping a lot, which made the headphones unusable.
Concurrently, I had another problem. The stereo jack on my laptop is kind of wonky. Probably has to do with the 3-foot drop onto concrete the laptop took a few years back (but it’s Lenovo – so it survived just fine). The problem is that it keeps dropping one of the stereo channels. It’s very annoying.
Solution – hack the broken headphones. Get rid of the speakers. Fit the battery and the Bluetooth chip into the same shell. Attach RCA plugs. Wireless stereo hookup for my laptop! (Or any Bluetooth-enabled music player, like my cell phone.)
This is the guide following what I did.
What you need:
- A small soldering iron fit for circuit work. A 12W or 15W with a fine point should suffice.
- A hand-held Dremel tool or something similar. I use the cordless Stylus, which I love dearly.
- A small phillips screwdriver, wire clippers, wire strippers, and an exacto blade.
- Two RCA plugs, some small-gauge stranded wire (I used 22), and heat-shrink tubing.
This is the shell that has the controls on it. I removed the soft comfort cover. The screws were covered by a retaining ring, which can be easily removed by hand. Take out the screws to reveal the innards!
Now that the shell is open we can the control circuit on the left and the speaker on the right. Remove the screws holding the speaker in place and cut its wires. You’ll notice the battery isn’t here – it’s in the other shell.
On the right-hand side of the circuit, six wires are attached, labeled as follows (starting from the top):
- SPRP – speaker, right, positive (brown)
- SPRN – speaker, right, negative (white)
- GND – ground (battery) (black)
- SPLN – speaker, left, negative (white)
- SPLP – speaker, left, positive (brown)
- VB – voltage bias (battery) (red)
The shell itself simply disconnects from the rest of the headband once the screw at the top left of the shell (as seen in the picture) is removed. There is a strip of soft rubber in the headband immediately next to the shell. It is glued in place and easily removed. The wiring is behind it. Cut the wires here, disconnecting the shells from each other.
Next, we go after the battery in the other shell. It opens the same way as the first – remove the soft cover and the retaining ring, the remove the screws.
Cut the red and the black wires to free the battery (they match to the same wires in the other shell). You now how a power source! Now, to fit it into the other shell, which wasn’t designed to hold it.
The space that used to be occupied by the speaker is almost big enough for the battery, but not quite. This is where the Dremel comes in – you need to make some space for the corners of the battery. This was the most tedious part. It’s hard to say how much you need to remove, but make sure the shell can close without clamping too hard on anything.
Now the battery neatly fits into the other half of the shell. Solder together appropriate wires – connect the battery to the control circuit, then connect the speaker leads to the RCA connectors, with enough length to give the wires a few inches of freedom outside the shell.
I connected the negative leads to the outside of the RCA connectors. I don’t think that really makes a difference though – it worked both ways with a pair of speakers I had at my desk.
The wires used in the headphones are of very small gauge, so stripping them is difficult. I used the exacto blade to carefully slice the sleeve and then strip it away. A more adventurous soul may wish to de-solder the leads from the circuit and attach leads of heavier gauge.
Important – the solder connections have to be insulated. Cover the joints with some heat-shrink tubing. It’s superior to electrical tape.
That is it! Close the shell, and screw it back together.
Overall, this took me a few hours (I did lots of poking around, and it took some time to figure out how to fit the battery in). The RCA plugs cost me a dollar at the local electronics store. Working with tiny wires is hard, but otherwise this doesn’t require much finesse.
Here’s the final product:
As I’m writing this, I’m listening to blues streaming from my laptop to the stereo system over Bluetooth. It sounds excellent.
Filed under: Hardware hacking | Leave a Comment
Tags: bluetooth, hardware hack, stereo, stereo hookup
No Responses Yet to “Bluetooth stereo hookup”