This howto shows you the schematic of a popular TDA2030A amplifier DIY kit which is sold on eBay and other places.
After ordering the kit on eBay (search for “TDA2030A Audio Power Amplifier DIY Kit”) I received a version 1.0 PCB made by XY HI-FI with components and a short Chinese manual on what was needed to solder the kit in stereo mode (OCL) or in mono mode (BTL or bridge). Bridge mode doubles the output power and can be used to drive a sub-woofer loudspeaker. I cannot read Chinese and thus searched for an English manual but did not find any. I decided to reverse engineer the layout of the PCB to produce a schematic and better understand what I was building.
What I find worth noting is the way the designer routed the GND signals on the bottom of the PCB. They are all concentrated to where the power is supplied. This is needed because high power parts of the circuit could offset GND to a non 0 volt level and cause problems in the low power parts or other high power parts.
After carefully inspecting where all the traces go I came up with the following schematic. The schematic is mostly similar to the reference schematic in the TDA2030A datasheet. I used the one that can be found on www.st.com (Doc ID 1459 Rev 2). The PCB cleverly combines bridge mode (BTL) and stereo mode (OCL) by not soldering C9 or R4.
The schematic is ordered in different blocks. Power and rectification, audio input and volume control, the left and right amplifier.
The power and rectification block rectifies the double AC voltage and stabilizes it into 2 DC voltages. The negative and positive voltage. You can use a symmetric DC source to power the circuit and connect it directly to C1 and C2.
Audio input is connected to a double RCA connector and the volume is controlled by a 50K ohm stereo potentiometer. I guess it is logarithmic.
The left and right amplifier block amplify the audio coming from the stereo potentiometer and output it to the PCB connectors on the right.
* The schematic shows extra diodes (D1 to D4). These are not on the PCB but I added them to the schematic because the are recommended by the datasheet. There purpose is to protect the output of the TDA2030A amplifier to voltages larger than the positive and negative supply.
The TDA2030A amplifier chip is protected by a thermal shutdown mechanism and can be short-circuited making it safe to use.
Let go solder the PCB and components into a working amplifier!
5x resistor 22K Ohm 1%. Color code: red, red, black, red, brown.
Bend the legs (1cm spacing) and then solder R1, R3, R6, R7. Optionally R4. After soldering, cut of the excess legs sticking out of the back.
R4 is only needed when you are going to drive 1 speaker in bridge mode. Do not solder when using the amplifier to drive 2 speakers in stereo mode.
3 terminal pcb screw connector.Solder it on the left side of the board next to the markings “AC GND AC”.
Note: solder it with the holes of the connector facing outward so you can later connect the power supply wires.
2x 2 terminal pcb screw connector.
Slide the connectors into each other in a way that you get a 4 terminal connector. Each terminal has a slot and ridge that interlock with its neighbor. Solder the now joined connector pair on the right side next to the markings “OUT GND GND OUT”.
2x TDA2030A amplifier chip.
Solder IC1, IC2.
Note: keep in mind that you align the chips so that they can be mounted to the same heatsink. Maybe now is the time to prepare the heatsink and drill holes. You can mount the amplifier to the heatsink using the isolation pad, isolation bushing and screw.
You are now done! Go hookup 1 or 2 speakers, a power and audio source.
If you are using bridge mode, the 1 speaker must be connected only to the two “OUT” connections. Do no connect GND when using bridge mode.
I soldered one on BTL (bridge mode) so C9 is not mounted:
During testing I played some MP3 files and the TDA2030A amplifier sounded good. (for the amount payed it amplified perfect.) I did manage to blowup the left channel by driving a small Mabuchi motor with a diode connected in series. This translated into a very hot TDA2030A, curious about when the magic smoke got out I ramped up the power supply and waited. Only the solder on the TDA2030A started to melt, but no smoke. I guess TDA2030A amplifiers do not run on magic smoke. Replacing the broken TDA2030A with a new one restored its function.
After the blown TDA2030A adventure I decided to mount the protection diodes. I guessed the voltage from a running motor feeding back into the amplifier is not something the TDA2030A can tolerate.
I mounted the diodes on the output, just as drawn in the schematic. The longer legs are protected by heat shrink tubes. On the left I connected the diodes to V- on capacitor C4. In the middle I scraped of some the blue solder resist and soldered the other pair of diodes to V+. The diodes are now here to protect the output from voltages greater then V- and V+.
Want to learn more about how the TDA2030A amplifier works? In the Youtube episode “SparkFun According to Pete 9-6-11″ the opamp is explained: http://youtu.be/OMJ9WGrRf6A
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