Behringer DI20

A cheap DI-box. It's a bit noisy so if your input into it is too low, you'll suffer for cheaping out on a higher-end DI-box. But as long as you have a healthy enough signal, you'll be fine.

As two examples:

My Telecaster was fine.
My very-low-output acoustic guitar pick-up was way too quiet so the hiss was as audible as the guitar due to having to crank the gain after the DI-box. To be fair that guitar pick-up really needs a preamp to behave, but it's good to know that it's not intended for extremely low signals.