It is obvious but let me state this before we start. BE VERY CAREFUL WHEN WORKING WITH ELECTRICITY. UNPLUG ALL BEFORE STARTING TO DISASSEMBLE ANY ELECTRIC/ELECTRONIC DEVICE AND USE PROPER SAFETY MEASURE. FAIL TO DO SO COULD CAUSE SERIOUS INJURY OR EVEN DEATH. Of course I'm not responsible for any damage, injury, death or stupidity. BE CAREFUL AND DON'T KILL YOURSELF OR THE OTHERS.
Ok that said,
Hello fellow makers
I've been a member since '09 and always enjoyed great instructables. Brief search doesn't show adding bluetooth to an existing power amp so I decided to share this very simple mod.
My wife wanted a bluetooth speaker, she doesn't listen to music much anyway. I didn't want to spend like $200 on it so I just added bluetooth to what I have.
This instructables directly covers power amps using 12-24VDC adapter, I used Lepai 2020a+($20 on amazon), if yours has a transformer on the board you need to use your multimeter to figure out where you get the lowered voltage and what the voltage is. If yours powers directly from the wall, you might just add a plug within the amp, so you can directly run a regular usb charger from there.
Step 1: Disassemble
What good is there if you just accept what you're given with? Take it apart by tampering(unscrewing) 4 anti-tamper bolt on the front side. I started doing this at night at home(not at the lab-no tools) so I just used IKEA pliers to grab the outside of the bolt head to unscrew.
You don't need to unscrew the pot on the front like the picture. They just can come out all together.
Also unscrew all on the rear to be able to slide out the whole innards to the front.
When everything is unscrewed and out it looks like this.
Step 2: Prepare(dismantle) Bluetooth Audio Receiver.
I bought this for $5.80
Get the one with at least physical audio output, not the one that is supposed to be read via USB directly from the device.
And also this for $1.84
For both, it costs $7.64
Crack'em both open once you receive it.
1. Cigarette power
Cigarette port has positive on the tip and negative on the ring. Now check polarity of the adapter - Negative on the outer ring - add wires from the power terminal on the amp to the cigarette charger. Didn't have flux on had so I lightly sanded the contact points.
2. Bluetooth audio receiver
Once you open it it is pretty obvious. Connect wires to 3 soldering pads on the audio terminal on the receiver.
Step 3: Solder Wires to Amp
Solder the wires from cigarette charger to the adapter terminal. They both are powered by 12V DC. If your amp runs on 24V it is also fine to use cigarette adapter. If your amp runs on higher voltage or powered directly from wall socket, you can switch cigarette adapter to proper down transformer or wall socket usb charger.
I initially used yellow and purple wire(no wires around) but later changed to a longer red and black one at the lab.
Find proper connections for the audio input and solder the wires from the stereo audio input to the bluetooth audio receiver. I scribed "T" for the tip, and "M" for the ring. I tested connection with little led and a 3v coin cell since I didn't have the digital multimeter home.
I cut off a little on the edge of the board for the wire to pass through. Now connect it to the bluetooth receiver accordingly.
Step 4: Add Output
You've directly soldered audio out to the amp but what about the existing 3.5mm stereo out on the bluetooth receiver? In case you want to add a powered subwoofer or something, I drilled the back panel with 5.5mm drill bit and wrote "output". Place bluetooth receiver and add hot glue to secure in place.
Step 5: Test Bluetooth Connectivity Then Put It Back All Together.
Yup. I got it.
Put'em back together. Adding bluetooth logo, cut out from the receiver casing could differenciate your amp from the others.
Look ma, no input wires!
Thanks for reading!