Made an electret mic preamp circuit, but how to eliminate mains hum? Answered
The circuit's purpose is to be able to listen to heart sounds and output it in a PC and the heart sound frequencies usually fall under 20 to 100hz. The problem is when i plug it in my laptop, i start to hear the hums. But when my laptop is just powered by the battery it completely removes it. Is there another way to eliminate the hum without having to run my laptop on my battery?