Introduction: Home Sound System

This audio system is simple to make and inexpensive (less than $ 5 plus some recovered materials found in my workshop).

Allows a strong enough audition for a large room.

As signal sources can be used:

-Bluetooth from any mobile phone.

-MP3 from a memory stick.

-Audio signal from radio signal in the 88-108MHz range.

-Audio signal from any audio external source (Line input).

The sound is reproduced in two external speakers 15W / 4om each.

Controls can be made from the front panel or from the IR remote control.


1. From AliExpress: Car Kit Bluetooth Reciver MP3 Player. Price: less than $ 5 including shipping.

Although it is intended for mobile applications, i will have no hesitation in using it in stationary mode.

2. My own workshop: all other materials and components.

Step 1: Schematic Diagram

The circuit is powered from the mains through the transformer Tr which gives secondary 16V / 1.5A.

This is followed by a recovery by D1-D4 then filtration with C13. A voltage of approx. 20Vdc is obtained.

This voltage supplies the stereo amplifier built with U1 - TDA2009, which gives 2x10W in the external speakers Dif1,Dif2.

The voltage regulator U, LM7812 gives 12V to supply the module "Car KIT bluetooth". It is also supplied by the voltage Vc = + 20V.

The presence of the supply voltage is indicated by LED, D5.

Step 2: List of Components, Materials, Tools.

See Photo1.

1. Car Kit Bluetooth Receiver MP3 Player. 1pc. Contains remote control.

It is the only component bought, I already had the others in my workshop.

2. Power audio board with TDA2009, which will be made as shown below. 1pc.

3. Power supply board. 1pc.

4. Power transformer that can give 16V / 1.5A in secondary. 1pc.

5. Network switch. 1pc.

6. Speakers connector 1pc.

7. Metal box recovered from an old PC (power supply box). 1pc.

8. Power cord from this power supply. 1pc.

9. Self-adhesive foil needed to cover the metal box. approx.16X35 cm.

10. Screws, nuts.

11. Matt white plastic foil(photos 4,5 ).

12. Heat-shrinkable varnish ,3mm. diameter, aprox 30cm.

13. Silicon grease.

14. Screwdrivers.

15. Digital multimeter (any type).

16. Fludor, soldering tools, cutter for component terminals.

17. Hot air gun, for working with 12.

18. Tools for metal drilling, filing, metal cutting for mechanical processing of the box

(you have to know how to play with them).

19. Lust for work.

Step 3: Making PCBs

The PCBs are made of 1.5 mm thick FR4 ,double sided. No metallic holes.

The crossings are made with uninsulated wire.

After echting and drilling, cover with tin, manually.

We check with the digital multimeter the continuity of the routes and the possible short circuits between them.

PCBs are designed in ExpressPCB, a program that can be used freely.

It can be downloaded freely from the Internet.

At the address:

there is the design of the power amplifier, power supply and other details of project.

You can download the PCBs design that contains all the elements necessary for execution,

of course if you have ExpressPCB installed on PC / laptop.

Step 4: Mechanical Assembly and Box Cover.

Using screws and nuts, the subassemblies are assembled as in photos 2, 3, 4, 5.

Then disassemble all the components. For the front and rear panels, cut the matt white plastic foil accordingly

(photo4,5) and stick them on the respective panels.

Cover the lid with self-adhesive foil (the same can be done with the bottom of the box).

To do these operations, you can consult the corresponding section of the tutorial:

Then reassemble the components.

TDA2009 and LM7812 will be mounted with silicone grease and screws on the bottom of the box, which will act as a radiator (photo 2,3).

The hardest part is over!

Step 5: Wiring and Putting in Function.

The wiring is done according to the schematic diagram and photos2,3.

The antenna (for working as a radio) is a wire of approx. 50cm. which is removed through the back panel of the box. Black wire in photo 5.

This device works with dangerous voltages for human life!

It is strongly recommended that the manufacturer be a person with experience in electrics!

On the power circuit the wires must have good quality insulation!

Special attention will be paid earthing the box, using a socket and earthing cable!

Be careful when connecting the white-green grounding cable (photo 2,3)!

Heat-shrinkable varnishes will be used after soldering the wires to the pins (photos2,3).

Putting in function is done by measuring the voltages according to the schematic diagram with the digital multimeter. Check that they are correct.

The next step is to see that the digital display lights up correctly, that the main commands are executed and that once a signal is applied, the sound is heard clearly and loudly in the external speakers.

Then we can move on to the next (and most enjoyable) step:

Step 6: Using

The system can be used in the following ways of working:

1. Bluetooth player.

Establishing a connection to an Bluetooth device. This can be a mobile phone (main photo).

Controls (volume, tone, choice of songs) are made from the phone player.

2. MP3 player (see photo 6).

Insert a memory stick into the USB connector. Switching to USB mode is done

automatically when the stick is inserted.

On this stick we must have audio information in MP3 format, to be recognized by the system.

Controls (volume, tone, choice of songs) are made from remote control or on the front panel of the system.

3. Radio.(see photo 7).

Entering this mode of operation is done by successively pressing the M button

on the front panel or MODE remote control.

We position the black antenna wire for optimal reception.

The radio stations are inserted in the memory after scanning the frequency band,

by pressing and holding for 3...4 seconds the SCAN button.

The stations will be entered in the memory in the order in which they were found.

Scanning may take some time.

Finally, the frequency of the received signal is displayed on the front panel.

Controls (volume, tone, choice of stations) are made from remote control or on the front panel of the system.

4. Power Audio Amplifier.

Photo 8 shows how to connect the external speakers to the system.

A low level audio signal from an external source is applied (photo 9).

Switch to Line mode by pressing successively the M button on the front panel or MODE on remote control.

Controls (volume, tone, ) are made from remote control or on the front panel of the system.

For a high level audition it is strictly necessary to have understanding neighbors. Otherwise it is better not to do it.

And that's it!

Audio Challenge 2020

Participated in the
Audio Challenge 2020