Yesterday I found an amplifier circuit using the TDA2003. There are 2 of them (ready to use), both 6 watts, one is mono and the other one is stereo. They are cheap, so if it works, I could get one. What do u think? Or should I build it?
The best setup with these small transformer-modulated rigs is to use TWO bridged devices like the TDA2003 - or - a Class D stereo chip in PBTL mode, connecting one output to each side of the audio winding on the modulation transformer. In this fashion you can avoid grounding one side of the winding - which in some cases - can create a path for ground loops and RFI. However, my advice to you is to just get a transmitter working. Then as you learn, you can improve on your build over time. I would recommend the mono amp and calculate for FOUR ohms on the audio winding. Its much more do-able at your level of expertise. Have fun!