> From: eric@...
>
> The device I'm connecting to the Polaris is one of those $10
> made-in-China USB MIDI interfaces, so I'm sure strict
> adherence to the spec wasn't their top priority. ;^)

I have a cheap Chinese interface too. It's black, oval, and has a stylized G-clef on it. If that's what you've got, be careful: it has a bug which causes it to swap the order of two incoming bytes every once in a while, so I don't use it any more, except for crude testing.

> Also I made an assumption that I probably should not have
> made... they may well be using pin 2 as the return and not
> the shell. I think I just read somewhere that some
> interfaces use the shell as a ground/return so I assumed
> that's what this device was doing.

USB MIDI interfaces are powered off the USB. They shouldn't be taking power from pin 4 of their input (the synth output), or need the ground on pin 2.

> According to the Polaris schematic, pin 2 and the shell of
> the MIDI output connector are both connected to chassis
> ground. I'm not too keen on connecting the shell to digital
> ground, but connecting pin 2 might not be so bad? If it
> turns out the interface is using pin 2 as a return maybe I'll
> try that.

The first thing to try is just to cut it. If the interface stops working, then try connecting it to digital ground. I'll throw a few Molex KK-100 contacts in when I send your panels today, so you can connect pin 2 on the MIDI OUT DIN to pin 5 on J11. I think those contacts will fit into that body.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...