TDA2003-based amplifier

I built this amplifier quite a long time ago and I still use it quite often (it is currently connected to my main PC). It's a very simple amplifier with acceptable performance.


Schematic diagram
Schematic diagram (click for full resolution)

This amplifier is based on the TDA2003 chip (Note: ST stopped manufacturing these chips some time ago, but it's still possible to buy them on various sites, and UTC still manufactures them). There are two TDA2003s on separate circuit boards in my amplifier, one for each channel. There are also a few resistors and capacitors for DC blocking, filtering, etc. The circuit is almost identical to the one from the datasheet, but there are a few differences. The gain is set by R1 and R4 to 23 (~27 dB), this is considerably lower than the "original" value of 101 (~40 dB). That was too much and the input was too sensitive. I also had a problem with the amplifier oscillating, this was supressed by replacing the capacitor in the Zobel network (C6, R3) with a bigger one (100 nF vs 220 nF).

The power input is fused by a 5 A fuse. There also is a third circuit board, with a 1N5408 diode connected antiparallel across the power supply input, a filtering capacitor (2200 µF).

The entire device is fitted inside a regular plastic electronics project box. There is a small heatsink at the back of the box to keep the TDA2003s cool, and a switch, an LED and a logarithmic stereo potentiometer on the front panel.


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