(1) Do you really need all 8 pins of a DOUT for drum machine dynamics?
I’m planning to use 6 pins for the resistor network like the original TR909 design. The two remaining pins can be used for the gates.
Even if you use 4 pins, that could still allow 16 levels per sound and you could use a single DOUT IC for two voices’ dynamics.
Yes, using 4 pins instead of 6 could be an option if somebody wants 16 velocity outputs instead of 10
(2) How do you plan to add such a great deal of velocity control to the MIDIbox 808 UI? The TR-909’s two dynamic levels are cycled through as you press each step (“GP”) button.
I’m not planning to overwork the MB808 application, e.g. because of effort reasons (meanwhile programming PIC assembly is a pain in the *ss for me ;))
And I don’t want to change the existing pattern structure (individual accents for each step would increase the pattern size dramatically, much less patterns could be stored than before)
Therefore we will still have only a single track which enables/disables accent for all other tracks.
Only difference is, that the velocity level for accented and not accented notes can be configured for each instrument.
The accent levels can be controlled individually if drums are played via MIDI.
(3) I haven’t looked in great detail at the 9090 schematic, but I believe it somehow uses the only a single resistor array to achieve full dynamics for all drum voices.
The 9090 uses some S&H stages to multiplex the velocity levels.
This has two disadvantages: the S&H stages have to be refreshed each mS by the firmware, this increases the CPU load.
Another disadvantage: it isn’t possible to set the trigger at exactly the same moment with a new velocity level - velocity would have to be set earlier, this adds an unwanted delay to the trigger.
Since the original design doesn’t use S&H stages as well, I prefer to go this way.
(4) Finally, I wonder if MIDIbox 808 is still a good name for this project, for a couple of reasons. The MB-808 is a TR-808 clone, of sorts, and a MIDIbox-based drum sequencer powers it. The sequencer is similar to the TR-606, and soon also the TR-909/TR-707, but it expands on those sequencers with numerous really cool, modern features. The name “MIDIbox 808” leads newbies to believe that the ucapps project is an 808 clone, when in fact it is much less (no sounds) and also much more (more comprehensive sequencer). Maybe something like “MIDIbox0x” or “MIDIbox beatbox” or “MIDIbox drumSEQ” describes what you’re doing without suggesting that it strictly clones the 808, and also distances this multipurpose sequencer from the MB-808 project.
I see the point…
But currently I’m only planning to add a small extension to an existing project with as less effort as possible, renaming the project could give you the wrong sign that this is a new project which is open for adding much more extensions. Thats definitely not the case. 
However, how about MIDIbox SEQ V3D
Best Regards, Thorsten.
