Building a digital sandbox

[blocky]

Hi everyone. I'm quite new to the site and to electronics in general. I'm starting an electrical engineering degree and trying to learn about circuits and guitar effects at the same time. I had an idea and right now I just want to know if it's feasible.

In a nutshell what I want to have is a test bed for trying out pedal circuits without bothering with a prefab PCB. H I have a bit of coding experience so I think I could figure out the software to stream either a generated sine wave or an actual audio sample out, and then bring the output signal back in and display the waveform and hear the difference. What I don't know is how the hardware actually works. What will it take to feed an analog signal into 2 pins of a breadboard, into some sort of signal-shaping circuit, and back into the PC? Will the voltage/current be at the correct levels or will I need some sort of step up/down? Is it safe to run this right back into my computer or should I have a 'failsafe' of some sort to prevent carelessness from blowing up my computer?

If a pedal can take a 9V battery and turn one analog signal into another at the same level, I dont see why this would be any different. Does such a product like this exist? If not I think it will be a great way to learn about signal processing and electronics at the same time.

Looking forward to hearing any feedback (no pun intended)
Cheers