[sdiy] MIDI phantom power...over 5 pin MIDI connector ?

[rsdio at audiobanshee.com]

On Sep 11, 2015, at 5:10 AM, Neil Johnson <neil.johnson71 at gmail.com> wrote:
> Instead of speculating wildly, how about looking up what happens in
> the real world?
> 
> Now, according to the gearslutz page that Barry linked to:
> https://www.gearslutz.com/board/electronic-music-instruments-electronic-music-production/885156-midi-solution-quadra-thru-hell.html
> 
> there were problems with the Aka MPC500.  No shit.  Why?  Go here:
> 
> http://www.synfo.nl/pages/servicemanuals.html
> 
> Download the schematics of the Akai MPC-500.  And lo, on page 11
> bottom left, it runs the MIDI interface from the 3V3 rail via 47R
> resistors.

The 47 ohm resistor is a better choice than 51 ohm, because it guarantees a minimum current of 5 mA, rather than slightly under that. The example MIDI circuits seem to be designed for a minimum of 5 mA, but will produce slightly higher current if temperature or other component values vary.


> Also on the synfo page you might also find the schematics of the
> Roland XV-5080 interesting (page 35) and Kawai K5000 (page 54).