MB SEQ and ROLAND MC-909

MIDIbox SEQ
1

Hello,

I am unable to use my Roland MC -909 with the Midibox seq I just built. Here is a summary of the testing I have done:

  1. Connect lpc-17 midi out 1 to MC-909 midi in. Set the appropriate ports and channels on the MB-SEQ to route a track to the midi output. - MC-909 does not respond to notes, CC#, clock, NOTHING! I have also tried live play and triggering from an external controller, and I can see the notes coming in and out with the MBSEQ midi monitor, but nothing happens on the MC-909.

  2. Connect ext. midi keyboard directly to 909 to make sure it’s working - everything behaves as expected. Notes trigger, CC#s register, etc. - this tells me that settings on the keyboard, and the 909 are correct. - now I think the problems is with the output of the MB-SEQ

  3. Connect the MB-SEQ to my computer via midi interface. When I look at the incoming messages in midi-ox, notes and CC#s are transmitted as expected. Ext. keyboard is able to pass through the MBSEQ and play VST’s and etc…

This leaves me stumped. I thought maybe it was an issue with using USB to power the MBSEQ, so I hooked up a 7.5v 1-amp power supply and although my LCD backlights are a little brighter, The MBSEQ still won’t trigger the MC-909

Can anyone suggest another test or idea? The midi settings in MC-909 are very limited and simple. I don’t think it’s an issue on the 909 anyways since it works fine when I take the MBSEQ out of the equation.

Thanks for your help!

2

It gets more interesting!

  • If I pass thru another synth or midi device that has a soft thru (where midi in is routed to midi out via internal processing, for lack of a physical midi thru jack) then is works perfectly. The MC-909 responds as usual. So why doesn’t it work when connected directly? Could it be a faulty optocoupler? Or perhaps MBSEQ is spitting out some data that the MC-909 doesn’t like, which gets filtered out by an intermediary midi device?

What do you guys think? It’s nice that I’ve found a workaround, but it’s going to bother me until I figure this out!

3

The core module sends MIDI OUT at 3.3V level.

100% compliant MIDI devices are able to handle this, but older gear sometimes doesn’t

This also explains, why it works when the MIDI signal is routed through another devices. Normally MIDI Thru is buffered, and by doing this, it will probably be shifted to 5V which then works with your 909

As another workaround (if you don’t like to sacrifice a MIDI Thru of another MIDI device), you could build a 5V level shifter by yourself.

E.g. based on a 74HCT541

Best Regards, Thorsten.

4

This totally makes sense!

Instead of cutting traces on my lpc17 to route to the level shifter, can I just install a IIC midi module and supply it with 5v?