Ralf Mardorf ralf.mardorf at alice-dsl.net
Sun Sep 2 14:15:04 CEST 2018

On Sun, 2018-09-02 at 07:26 -0400, Paul Davis wrote:
> On Sun, Sep 2, 2018 at 3:02 AM, Will J Godfrey <WillGodfrey at musically.me.uk> wrote:
> > As a matter or interest, the only time I've had missing noteoffs with
> > standard MIDI was when I had only a single MIDI port, and daisy-chained a sound
> > canvas and two keyboards (both sending active sensing). One for the
> > keyboards also had a pedal attached. Having said that I always used good quality
> > short cables.
> a couple of days ago, while working on MIDI Clock support in ardour, i
> was trying to figure out the origin of some missing Clock (0xf8)
> messages. they would arrive every 830 samples plus or minus about 30
> samples,. but every once in a while, the gap would be twice that. 
> long story cut short: just changing from using my MOTU Ultralite AVB
> for MIDI I/O to a Midisport 2x2 fixed the problem. No more missing
> Clock messages. 
> could be relevant to stories like the one above. there's no good
> reason for this, but it is how things are.

Such an issue could be related to the used opto-coupler and diode or by
a trim potentiometer for sensitivity that isn't set up properly. I
adjusted the trim potentiometer of my DIY MIDI throu box build in the
80s to work with old gear, but nowadays USB devices not always provide
enough current to drive the MIDI throu box with this adjustment. I heard
of issues related of slow opto-couplers or diodes to fix slope issues,
but never experienced this myself.

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