One day Mike and I went to the local RadioShack and Mike got excited about an amplified speaker for an iPod which looked like a guitar amplifier. I suggested building similar one ourselves.
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Schematic and PCB Layout
See attached files at the bottom of this page.
The amplifier is based on ST TDA2003 integrated circuit - a 10W car audio amplifier. The circuit we used pretty much follows the application circuit in the TDA2003 datasheet. Mike and I drew the schematic and designed the PCB using KiCad suite and ordered PCBs at OSH Park ($14.25 for a set of 3 boards). Most of components are mounted on the PCB, excluding volume control potentiometer, audio and power jacks, and speakers. We mounted the PCB on an aluminum plate (the plate initially came with RadioShack project enclosure) using IC thermal pad and a single 3 mm screw. So that the aluminum plate also works as a heatsink. We put some thermal compound between IC and the plate. Audio and power jacks, and the volume potentiometer are mounted on the same plate as well.
We reused drivers (speakers) from an old non-powered computer speaker, that Mike got for free at the local surplus store (they give kids a bucket and there are a few shelves that kids can dig for free stuff). The speaker box is built from 1/4" (6 mm) MDF, 4 wooden planks and some wood screws. We glued it with wood glue, and sealed the seams using a hot glue.
The speaker has a stereo input, so that a device with stereo output (like an iPod) can be connected to it. The stereo signal is converted to mono signals using a couple of 1 kohm resistors soldered on the audio jack. One lead of each resistor is connected to the input on the audio jack (one resistor to the left channel, another one to the right channel). Two other leads of both resistors are connected together and then connected to the volume control potentiometer.
Bill of Materials
| Component Type|| Reference || Description|| Quantity|| Possible sources and notes|
| Printed Circuit Board|| || Gerber and KiCad files provided below|| 1|| Order at OSH Park or make it yourself. See attachments for Gerber files.|
| Integrated Circuit|| U1|| ST TDA2003A|| 1|| Mouser 511-TDA2003AV|
| Capacitor|| C1|| Ceramic Capacitor, 8.2 nF|| 1|| Mouser 810-FK28C0G1H822J|
| Capacitor|| C2, C3|| Ceramic Capacitor, 0.1 uF|| 2|| Mouser 810-FK28X7R1H104K|
| Capacitor|| C4|| Electrolytic Capacitor, 10 uF, 50V|| 1|| Mouser 647-UKT1V100MDD|
| Capacitor|| C5|| Electrolytic Capacitor, 470 uF, 50V|| 1|| Mouser 647-UKW1V471MPD|
| Capacitor|| C6, C7|| Electrolytic Capacitor, 1000 uF, 50V|| 2|| Mouser 647-UKW1V102MHD|
| Resistor|| R1|| Metal film, 1 ohm|| 1|| Mouser 660-MF1/4DCT52R1R00F|
| Resistor|| R2|| Metal film, 4.7 ohm|| 1|| Mouser 660-MF1/4DCT52R4R70F|
| Resistor|| R3|| Metal film, 100 ohm|| 1|| Mouser 660-MF1/4DCT52R1000F|
| Resistor|| R4|| Metal film, 470 ohm|| 1|| Mouser 660-MF1/4DCT52R4700F|
| Resistor|| || Metal film, 1 kohm|| 2|| Mouser 660-MF1/4DCT52A1001F|
| Connector|| P1|| Pin Header 2x1, 2.54 mm lead spacing|| 1|| Mouser 649-68002-102HLF|
| Connector|| P2, P3|| Screw terminal 2x1, 5.00 mm lead spacing|| 2|| Mouser 651-1935161|
| Connector|| P1|| Pin Header female connector|| 1|| Mouser 855-M20-1060200|
(Note: this is a 100 pieces bag of contacts, only 2 are needed for this project)
| Connector|| || 3.5 mm stereo audio jack|| 1|| RadioShack 274-249|
| Connector|| || 5.5 mm x 2.1 mm DC jack|| 1|| RadioShack 274-1563|
| Potentiometer|| || 10 kohm audio taper, with switch|| 1|| RadioShack 271-215|
| Knob|| || Knob for the potentiometer|| 1|| RadioShack 274-424|
| Speaker|| || 8 ohm speaker|| 1|| We used two speakers: one low-mid range and one high frequency (tweeter) connected through a crossover capacitor.|
| Wires|| || Color wires to connect the board to external connectors, potentiometer, and speakers|| 1 m|| Use color wires: e.g. black for ground, red for power, different colors for audio in and audio out lines.|
| Power supply|| || 12V / 1A DC brick-type power supply|| 1|| Amplifier IC needs supply voltage to be in 8V to 18V range. |
| Speaker box|| || MDF, wood, screws, etc.|| || Home Depot 1/4" x 2' x 4' MDF|