Hello!
This is a revisted version of my previous, improperly made question.
It would be great if the moderator (please) delete the previous one, I had provided the link to avoid littering.
My goal is to drive a load when the bass of an audio signal reaches certain threshold. To do that, I have modified an existing circuit.
I know 741 is an old lousy IC, but such simple task is an alternative to the trash bin. Filter works great, bass sounds awaful, but at least corresponds to the frecuencies (and the peaks) that I need. By the way, gain is still very low. I have to set the volume of my test amplifier all the way up, to hear the beats of the 741.
The problem is, the transistor doesn't respond. I've adjusted the resistors for maximum gain as possible without oscilation, but either stays on or off all the time. Only when The 741 starts oscilating violently the light of the LED corresponds with the machine-gun like sound.
Any advice would be great!