Static noise in audio mixer

Thread Starter


Joined Nov 4, 2014
Hi all,
I built an audio mixer out of op amps to combine a microphone and music signal. There are two pre amps for each signal, two potentiometers, a summing amplifier, and a power amplifier for the speaker. However, there is a LOT of static noise, sounding like crackling, when in use. No static or buzzing when there are no signals being inputted, but a LOT of static when the signal connections are made. I thought this could be caused by electromagnetic fields interfering with the signal. Maybe, it could be caused by loose connections. Or, it is most likely some design fault. What do you think I should do to cut down the static? Also, the microphone signal is very odd sounding because I don't hear everything I'm saying into it on the speaker.
Thanks for the help.