Aux in for V-Twin

[beedubyayardee]

I have a very old V twin pedal. I have just dusted it off, and I’m working it back into usage. I’m really enjoying it. However, I have a question. I do like the fact that I can plug it in and listen with headphones and not need to drive an amp in order to practice. it would be great to figure out how I could get an aux feed so that I can play along with an audio source?

Any ideas?