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About 4 years ago I made a Small Entertainment System from cheap music modules obtained from Ali-Express and similar sites. The main problem with the modules back then was there was no built-in amplifier so you had to add your own. Recently I came across similar modules with built-in amplifiers so I thought try one out.
The module I used claims 25W per channel. There is even a 100W per channel version. There is no way either of these can output anywhere near this power. These ratings are what is known as music power, a completely made up power rating used for marketing purposes. True power measurements are quoted in RMS power. I would guess the 25W amplifier puts out around 2W to 3W RMS power at best. This is more than ample for an internal room in a house.
PartsAll parts were sourced from Ali-Express. The parts should come to around AUD $20-$30.
1 off 50W Amplifier Bluetooth 5.3 MP3 WMA APE Decoder Board Microphone USB TF FM DIY Music Player AUD $8.29
2 off 8Ohm 2W Speaker Diameter 77MM
1 off DC-022B 5.5x2.1mm DC Panel Socket
1 off PJ301M 3.5mm Audio Jack
4 off 2 Positions Jack Spring Load Audio Speaker Terminal
1 off FM L-Shape Radio Antenna 3.5mm Retractable
16 off 4x4.2 M3 Brass Inserts
4 off 5x3.5 M2.5 Brass Inserts
8 off M3 6mm Black Hex screws
4 off M2.5 4mm Black Hex screws
8 off M3 6mm Screws
3D PrintingThe STL files for 3D printing are attached. All parts are printed using a 0.2mm layer height. No supports are required.
"MP3 FM Module V2.stl" - Rotate 180 degrees around X-axis
"MP3 FM Speaker V2 - Box.stl" - Rotate 180 degrees around X-axis - Print 2 off
"MP3 FM Speaker V2 - Back.stl" - No rotation required - Print 2 off
"MP3 FM Speaker V2 - Mount.stl" - No rotation required - Print 8 off
Main unit assemblyStart by heat pressing in four 4mm deep x 4.2mm diameter M3 brass inserts. Make sure you use the inserts designed for plastic and not wood. See image in the Parts section.
Solder a wire to the front pin on the PJ301M 3.5mm Audio Jack. Place a dupont female connector on the other end. This will be used to connect the aerial to the module.
Solder the free end of the power wire that came with the module to a DC-022B 5.5x2.1mm DC Panel Socket. The long pin is negative and the short pin is positive. You can 3D print the "Nut Driver Ex 11.stl" which will allow you do up the nut that holds the DC panel socket in place.
Solder the left and right speaker wires to the 2 Positions Jack Spring Load Audio Speaker Terminals. Screw in the terminals using M3 6mm Black Hex screws.
Solder a single pin header to the aerial hole on the music module.
Heat press in four 5mm deep x 3.5mm diameter M2.5 brass inserts. Make sure you use the inserts designed for plastic and not wood. See image in the Parts section.
Plug in the power, speaker and aerial connections and close the case. Use M2.5 4mm Black Hex screws when screwing the music module to the 3D printed case.
Start by heat pressing in four 4mm deep x 4.2mm diameter M3 brass inserts. Make sure you use the inserts designed for plastic and not wood. See image in the Parts section.
Using 6mm M3 screws, loosely screw the speaker holders onto the brass inserts. Place the speaker in the center and position and tighten the speaker holders.
Heat press 4mm deep x 4.2mm diameter M3 brass inserts into the back panel. Make sure you use the inserts designed for plastic and not wood. See image in the Parts section.
Solder the left and right speaker wires to the 2 Positions Jack Spring Load Audio Speaker Terminals. Screw in the terminals using M3 6mm Black Hex screws.
Create two sets of speaker wires to connect the speaker boxes to the music module. I used ferrules on each end to stop the wire from fraying but this optional. You can also just tin the ends with solder instead.
Plug in a 12V power brick. It should be able to deliver at least 1A.
To link to the unit via Bluetooth, click the MODE button until you see BT displayed. Connect your phone or device to JX-BT.
To set up the radio, click the MODE button until the radio appears and click the U/SD SCAN button on the infrared remote control. (Make sure you are pointing the remote at the unit - range is short so you need to be quite close). The unit will scan and note all the radio channels. After the scan is finished, you can go to each radio channel using the forward and back buttons.
ConclusionI am really pleased with how this project turned out. The module works well and looks really quite professional.
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