I worked with one of my lab partners to design a circuit that will take the output from a line-level stereo source and provide an amplified output that can be sent to a set of ear-phones. We made use of two 100kOhm potentiometers that would act as volume dials. We used non-inverting operation amplifiers to magnify the sound, and we used PSPICE to simulate and analyze different frequencies and outputs of our circuit. My role in this project was analyzing our proposed circuit and calculating the needed values for the correct output.
We independently supplied power to each of the operational amplifiers; the input for the potentiometers came from a split 3.5mm aux chord. Another split aux chord (right, left, and ground) was connected to the output of our circuit and then to speakers. Below is a picture of the circuit connected to speakers. A grey oscilloscope probe can be seen as well. We used the oscilloscope to trace the outputs of the right and left sides independently.