Last time I have featured an active Di box circuit. Here is a more simple circuit that only uses 1 JFET instead of an OPAMP.
This circuit is so simple that you can actually build it without PCB. You can also just use a universal board on this one. I actually copied this circuit from an acoustic guitar. haha! sure it works and I also have simulated it.
This circuit works well according to simulation, it actually works in actual.