the reason this is qualified as "experimental" is because it does work but I haven't found a use for it yet. I designed this primarily to see how well the 555 timer IC would reliably create the PWM at high enough frequencies for audio. I haven't done much testing other than a quick check with a signal generator/speaker to see if it worked and of course a few passes with an oscilloscope to make sure things were doing what they were meant to be doing. I used a LF351 op-amp pretty much because it was the nearest wideband op-amp to me. I often try to explain that the reason I choose certain ICs is not because they have some magical "warm" sound or any of the other shit audiophiles make up but because I have looked at the datasheet and determined it's the best part for the job based on the explained data within the data sheet, either that or I'm lazy and I know a specific one within arms reach will work.
this kind of amplifier requires an inductor, a value I didn't have to hand so I used some salvaged enameled copper wire from the secondary of a burned out mains transformer (24AWG if you need a wire size)
to make the inductor I wrapped 70 turns around a bolt from my massive box of all the screws I've collected over the years salvaging stuff, the bolt is about 5mm in diameter.and that will get you in the ballpark of 470uH I think mine ended up being 500uH ish.
anyway I will draw up the schematic maybe tomorrow but for now here is the veroboard layout
roger here. first time i have seen a simple classd amp.
ReplyDeletejust some comments...what will the 555 output??? perhaps 1/2 watt???
I build speakers and was looking for a bi-amp system when i found your webpage. i will use the tda2030 board layout.
keep up the good work with the strip boards. thanks roger