Add Bluetooth to Any Powered Amp for $8

by Minifacture

118K74034

Intro: Add Bluetooth to Any Powered Amp for $8

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,

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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

http://www.banggood.com/5V-USB-Wireless-Bluetooth-...

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

http://www.banggood.com/Wholesale-Universal-Mini-USB-Car-Charger-For-iPhone-4G-1000mA-Mp4-p-26136.html

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!

34 Comments

gauravsanu 5 years ago

Where to buy Lepy Lp2020a+ or Kinter K2020a+?
Can you help me please

Yaunclesam 7 years ago

there will be a lot of noise because the amp and the module share the power source . Use a ground loop isolator

bistrobros 9 years ago

Getting alot of static noise and clicking in my build. All components function perfectly independently. Anywone have a solution to get rid of the noise?

whoxismo 8 years ago

I have the same problem. I just soldered the car charger to the amplifier power input and connected the bluetooth module using the audio jack in the back. It works, but the background noise is terrible. Also, the noise seems to increase if I touch the cables, as if I was acting as a kind of antenna. If the volume is low in the amp and set to 100% in the computer, the noise can't barely be noticed. But as soon as you turn up the volume knob.. it's pretty annoying. Would around loop isolator work here? What about using a separate power supply for the usb bluetooth receiver?

lifeinbeats 8 years ago

I think it depends on the quality of the bluetooth module, but I just had some squelching with my build and I bought a ground loop isolator (Boss B25N) and that got rid of it. My Bluetooth module is external to my amp, though and connects to the amp via phono, so unfortunately if you're trying to fit everything in the amp housing, that may not be the right solution.

confoundedbridge 8 years ago

Could be a lot of things. If you are installing this inside any decent enclosure (i.e. most good amps) the case itself is a grounded electromagnetic interference shield (read: bluetooth shield). You'd want to put this outside of the enclosure or connect it to an antenna on the outside.

JeffP18 8 years ago

same problem here. Have tried two different 12v adapters thinking that was the problem, but it wasn't. If anyone has a solution, feel free to share. I think its a ground problem, but can't verify if i'm right.

Blackcloud161 8 years ago

I found that setting the volume on the phone to 50% and using the amp to drive the speakers works great.

This is most prevalent on Google Music.

Hope this very late reply helps

ikymagoo 8 years ago

Does the regular audio input still work after you add the module?

rmuga 8 years ago

just added this on my suitcase boombox and everything is working perfectly.

thanks man

masterleo 9 years ago

piece of art I Always was asking miself how it would be feasible.

But this was before ...

Raphango 9 years ago

Awesome! Congrats!

jasonp519 9 years ago

Thanks for the info, this BT is exactly what I need for my car radio.

moe44c 9 years ago

The (much) easier, but possibly less fun, alternative to this is to just buy a bluetooth receiver and a 3.5mm jack-to-RCA cable on Amazon. I have this exact setup in my house, and it works flawlessly and is always on and ready for pairing/connecting.

mbireta 9 years ago

All of the car bluetooth receivers that I have used in the past (in the car) timeout after 5 minutes or so of inactivity. If you attach a switch on the cig-bluetooth power input, you could cycle the power without having to power cycle the amp, which usually doesn't have a power switch. FWIW, in two years, I have had four of the cig-bluetooth adapters die for no apparent reason, Might be a pain to rewire an amp a few times per year. Have you run into any of these issues?

jasonp519 9 years ago

The no switch part is what I'm after. I added a BT to my car radio, but have to have it accessible due to the power/pair switch being momentary on. When power goes off, have to turn it back on every time. The pairing is automatic as well?

Minifacture 9 years ago

Yes if your device has BT on, then it automatically pairs.

rfitzgerald 9 years ago

My only suggestion would be to use a different type of glue to mount it in place, being hot melt glue, the charger itself as well as the heatsink it is mounted to inside the amp is going to get warm, quite possibly warm enough to melt the glue. Once it's all tested and working I'd recommend epoxy or similar as a more permanent solution

jumpfroggy 9 years ago

Hot glue melts at about 120c. Thats pretty hot. If your amp (even the heatsink) is getting that hot, I'd be worried something is wrong. These little t amps dont work with much power (compared to the full size ones), so they shouldn't be really hot. I think hot glue would be fine here. You could always use epoxy just to be safe, but I'd think it might be overkill.