The 20W amplifier project, as detailed in the last entry, was a partial success. It was working, in that the sound was being amplified, but there was a tremendous amount of humming. The other issue, which does not have anything to do with sound quality, was the part layout. The TDA2003s were on opposite sides of the PCB making it very difficult to attached to a chassis for heat dissipation.
So the circuit was rebuilt. This time a Radio Shack 276-158 PCB was used. The board previously used was cheap and poorly made, even with a low iron temp the pad were lifting off. The Radio Shack board is of much better quality, which made the assembly a bit easier.
The layout is mostly the same, except that the power ICs are now on the same side of the board. When placed inside the project case, they can be attached to the back or side for heat sink reasons. It would have been nearly impossible to do that with the previous layout.
Here’s a video demonstrating the working amp, note that the sound is recorded with the video and was not added later (recorded with a Motorola Moto X, which I will be reviewing soon).
Next will be the volume/tone circuit and then mounting it all in a project case… to be continued!