I'm trying to make my own class D amplifier out of discrete components then eventually sampling the output using LED.
So far, the class AB amp (to the right of capacitor CMPC) is working with lots of heat (guess that's my consequence for choosing TIP31C and TIP32 transistors instead of better ones).
The reason I want to explore class D amplifiers is because I could probably somehow turn it into a VU meter (a circuit that converts sound to light pulses) without generating heat and I'm afraid if I use a class A amp then I'll create more heat.
So I ran some tests starting with the 555 timer and ignoring everything else. I wanted to hear what a triangle wave sounded like. and I couldn't hear a thing!
I even modified the triangle wave circuit so it matches a standard astable multivibrator circuit made from a 555. I tested 555 pin 2 (by connecting a capacitor and speaker in series to it to ground) and no sound. As soon as I disconnected the speaker+capacitor from pin 2 and hooked it to pin 3 (the out pin), I get a high pitched sound (expected).
I ran the same kind of tests with LTspice and a connection to pin 3 shows a square wave from 0 to VCC. If I tested on the triangle wave output on both circuit configurations, I get a triangle waveform with a smaller amplitude. This time it goes from 0 to about 4.8V (which probably explains why I hardly hear anything).
Anyways, Instead of the above circuit, I connected pin 3 of the 555 timer to the amp input (on the 393) through a capacitor. I also connected an external sound source (my PC earphone jack playing loud music) to another input in the same amp (on the 393) then output to speaker, capacitor and to VCC (because LM393 output is open collector).
I got no results but when I switched the input source, I could hear only the local oscillator (from 555). I couldn't hear the music from the PC at all. I thought maybe I would hear pulses of sound since both inputs are changing but I don't even hear that.
Am I picking the wrong parts? or what am I doing wrong?
I want to see that I can get a normal class D amplifier to work from discrete parts before I move on to converting it to a stereo VU meter without heat.