This is the stereo power amplifier (class B) specially use in car radio. I use it in my project. I have to drive loud-speaker through it applying different type of input. 1.Input from MIC 2. input from mono audio source. 3. input from stereo audio source. 4. Both mono audio and MIC (mix audio signal.) there is no problem with mono input and stereo input but input from MIC doesn't work. I use electret MIC with preamp ( image 2) output of preamp is connected to buffer and then connected to the input of TDA 2004. next problem..... TDA2004 with 5Ω stereo speaker and input volume control 22k stereo pot ... when i increase volume to maximum sound distorted. may be supply problem or ... i used 18v supply.