This blog may provide interest to some newbie looking for low cost, easy to build class d amp source tuned to their listening taste. I have already tried this circuit on the breadboard and it sounds surprisingly good but I’m sure it will work much better on PCB of course. The timer chip I used is the CMOS LMC555 because it’s a lot faster than bipolar counterpart such as 15 ns rise and fall times and can oscillate up to 3 MHz @ 5V. Of course you can use bipolar 555 timer as well.
About the circuit:
The circuit consist of 2 classical yet popular configurations; The master wired as “astable multibivrator” and the slave as “one shot” monostable.

https://geekcircuits.com/wp-content/u...ive-filter.png
Figure 1.
Slave A is an active band pass filter tuned to 20 Hz with +/-7 Hz bandwidth serving as “mega bass enhancer” while slave B is a simple high pass filter with -3db roll-off at 7 KHz for the treble. Slave C will fill-in...