I'm developing a project on a board that uses 3.3V. And there has to be just one MIDI out. I tried connecting ground, vcc and data pins to a midi jack and it works fine with Kemper profiling amp. I tried it without any resistors as well as 220 ohm and 100 ohm on the 3.3V power pin (vcc) and there was no difference.
Is it better to use 5V than 3.3V?
What resistors are needed for each case and why?