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Here is a velocity control for each voice module of a TR-808. The concept is simple.. What i did is i took the accent circuit from the original schematics and i place a digipot that will control the velocity for every single voice separately. A Digipot chain will be connected at J19 of the STM32F4 Core. Each Digipot is controlling the Velocity Value on each instrument. So let's see. A Pin from Dout module sends a Trigger of +5 Volts. One Branch goes at the Trigger in of the Voice module. The other branch is going into my circuit. The digipot controls the velocity level from +5 volts to +15v. ( Even with 0 Velocity a 5v minimum trigger must go in voice module so we have sound.) The result is a Trigger voltage from +5v to +15v that goes into the Accent in of the voice module. What we have here is a velocity control for every single note. :rolleyes: I Need help on how to programm Digipots to do this job. Here is the schematic Accent 5-15v.PDF Regards Tilemachos

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On another note, if you are doing individual accent channels for drum voices, it seems much better to just control them via that drum's parameter layer instead of using up a different track. I'm not sure if the firmware can already do this or not (send to an extra DOUT based on a parameter layer.) If you REALLY wanted to beef up your 808's accent potential, you could hook up an AOUT board and send a velocity-dependent CV output to each drum voice's Accent input (added to 5v, to make the range 5-15v.) I know that would probably require all sorts of firmware adjustments and I don't think MB808 supports full Midi velocity, but in that case you'd have a full range of velocity for every drum voice on every step. :)

In order to answer your question, it's neccesary to understand the 808's circuitry a little better (I am assuming you are referring to the 808 drum voices.) In order to trigger, an 808 voice (such as the BD) needs two signals -- one at the trigger input and one at the accent input. Customarily, the accent input of ALL modules is connected to the same output from the Accent circuit (which includes the accent level knob.) What this means is that the accent signal must be always present when the drum is fired, even if there is no accent on that step. The difference in intensity/volume comes by the level of voltage at the accent input. When the accent circuit is not triggered, this voltage is 5V. When global accent IS triggered, this voltage is determined by the position of the accent pot (somewhere between 5v and 15v.) So to answer your question -- Yes, it is possible to have more than one accent channel. But your understanding of the requirements for the Accent signal are not complete. You can't just send an extra DOUT to the Accent input of the module and disconnect it from the global accent -- in that case you'd be hearing the drum ONLY on accented steps (since the drum requires both signals to trigger), and not at an accented velocity (since the accent voltage would only be 5v). In order to get the functionality you want, you'll have to clone the accent circuit from the schematics (which you can find on the eight-oh-eight.org forums) for each drum voice you want to have it's own accent. Please let me know if this is confusing. I have built several 808 voices for my modular synth and it's been a battle figuring out how it all works. :) Also I've discovered that you need a 1ms pulse only at one of the two inputs (Trigger and Accent) -- the other signal can be a constant voltage. I've successfully sent envelope or LFO signals conditioned to fluctuate between 5-15v to the Accent input of my 808 modules with good results. Also you can send the exact same trigger signal to both Accent and Trigger inputs and the drum will fire fine. So if you'd prefer to "deactivate" accent on one or several of your modules, rather than adding extra accent channels, you will find that much easier. :) Just cut the trace from the accent input of the drum voice to the global accent, and short together the trigger and accent inputs.