>Joystic port or MIDI port? Back in the days I only ever thought of the DA-15 as the Game port[1]. To me it was only meant to welcome a joystick and play flight simulators. Little did I know that it could also be used as an output to send MIDI commands to a MPU 401-UART!
With no latency of course because USB hadn't been invented yet.
>My SC-55ST came without a power supply. That was the opportunity to understand better the power requirement marking on the back. Voltage and Amperage are obvious but one must also pay attention to the polarity sign. The SC-55ST uses a negative center[7].
This is the "standard" for guitar effects pedals due to the ordinary switching power socket component on their PCB. The outer connector of the barrel jack does the switching by pushing the conductor away from the internal battery pole and over to the external supply when it is plugged in. This would switch the same way physically whether it was positive or negative, except these are often very sensitive or high-gain audio circuits and every bit of earth ground integrity can be essential for the metal enclosures and coaxial cables to shield the inner audio signal properly.
This SC-55ST may not have an internal 9V battery like a guitar pedal would have, but it was designed to run on a Roland "Boss" A/C adapter anyway which is the top shelf wall wart having highly regulated clean power for studio use. Roland set the standard for center ground with their Boss pedals and adapters which basically steamrolled everyone else. Since for this application it's not the power supply that's using any shielding at all, but the audio needs as much shielding as it can get.
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