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Midibox64 - 14bit Faders


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HI, yesterday i finished the first prototype of the Midibox 64 using the PCBs from SmashTV but only wiring up 10 pots and 2 faders. Were aiming to built a very small and light weight mixing panel for taking to parties or carrying in your back pack. We already have a behringer BCD3000 mixer but wern't happy with the resolution of the tempo faders for mixing purposes. Anyway we decided to build a midibox on the premise that longer faders would give us better resolution. I now know this to be wrong having read up properly about midi controllers and understanding better about how the midibox works. The pots and faders in the BCD3000 and midibox are being sampled at 8 bit and both give them same fader resolution, so far i havent gained much from creating my own mixer, only to cut down on unwanted knobs/features. From reading the midibox documentation it would seem that the midi protocol and indeed Traktor has support for 14bit data. I know the ADC on the PIC can only sample to 10 bit and the remaining resolution interpolated but this would at least give us a higher resolution to work with.

Has anyone had any experience with this or know if the application for midibox64 supports the 14 bit feature?

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Without an added ADC there's no way you'll get "true" 14bits. 10bits = 1024 values. I am not sure you can possibly move the fader in smaller steps. Assuming you used faders with 100mm travel, 10bit resolation means each "step" equals a fader movement of 0.09765625 mm. Are you sure you can move the fader less than that? ;)

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edit: Btw, "midibox" is a useless tag on this forum ;) Also, don't put spaces after the "," when you add more than one tag.

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Since the math is fairly abstract here's a pic showing my point. The content of the pic is to-scale. Can you really really move the fader in smaller increments than shown on the scale at the bottom (100mm fader travel @ 10bit)

5833_ea72ee26d73d751e9ea2d8a62eac0596274

5833_ea72ee26d73d751e9ea2d8a62eac0596274

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Thanks for the reply.

Just to clarify a few bits; im not concerned with motor faders, and am aware with there inaccuracies. The aim for me to undertake this project was to increase the resolution of the standard faders used for tempo adjust as at present we were unhappy with what we currently have. On the BCD3000 deck and likewise on our Midibox64 unit the midi controllers are both only sampling at 8bit, giving 128 values over a tempo range adjustement of +/-10%; Thus giving a step of 0.15% per bit. Indeed we could increase the resolution by reducing the tempo adjust range say to +/-5 which would give a step of 0.078% however in order to give this improved resolution we are loosing the range over which we can shift the tempo.

I understand your point about the resolution of a 14bit and the distance you would have to move a fader in order to shift it 1 step, but it was my understanding that inorder to sample a pot/fader higher than 7 bit and still be midi compliant we would have to use 14 bit sampling. I dont think the midi spec caters for anything other than 7bit/14bit unless im wrong? Heck even a 9bit or 10 bit sampling would be an improvement to the fader if we could do it.

Here was the bit about 14bit midi messages in the midibox wiki - scroll down to 14bit midi messages:

http://www.midibox.org/dokuwiki/doku.php?id=midi_specification

Im aware the PIC can only sample to a max of 10bit and the result would have to be interpolated to a 14bit scale but was wondering if their was facility in the midibox64 code to do this as it seems that both Traktor and the midibox OS has the facility use this extended sampling range.

Sorry for being a bit of a newbie to this forum/lingo/tags etc. :)

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Sampling the values doesn't have anything to with what you send. You can sample @ 10bit (which is what MIOS does) and scale to 14bits and send that. Or scale down to 7bits and send that. That's scaling and not interpolation btw.

Obviously you can't send the 10/14bit value as a CC, but you certainly can send it as NRPN or SysEx. Not sure if/how that's implemented in the mb64 app, but you can certainly add it if it's not there. From a quick quick look at Serge's editor it seems that you can assign pitchbend to a fader which is 14 bits. Even if that's not exactly what you need, a few lines of code will certainly let you get the full 10bits to your DAW.

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what hasn't been mentioned yet: at 10bit resolution it will become really hard to avoid some jitter due to noise from power supply and the like. so you will have a steady stream of little tempo changes. imho, a higher resolution is only sensible if you set the values digitally instead of a pot.

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10bit

perfect for me  :)

what hasn't been mentioned yet: at 10bit resolution it will become really hard to avoid some jitter due to noise from power supply and the like. so you will have a steady stream of little tempo changes. imho, a higher resolution is only sensible if you set the values digitally instead of a pot.

Which is what I'll be doing with my project.  Now all I need to know for sure is if the MBLC sends the proper ping back to the DAW to identify it's self as HUI or Mackie Control.

Sorry to hijack this thread...  I've asked in other threads, but no responses

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Now all I need to know for sure is if the MBLC sends the proper ping back to the DAW to identify it's self as HUI or Mackie Control.

Logic Control and Mackie Control are basically the same thing, only the "ping response" has a different ID (I think because of some dispute between eMagic and Mackie when they split up). You can select Mackie or LC mode by changing one option in the source code.

S

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Logic Control and Mackie Control are basically the same thing, only the "ping response" has a different ID (I think because of some dispute between eMagic and Mackie when they split up). You can select Mackie or LC mode by changing one option in the source code.

S

Yes, but are they the same as HUI?  It's tough to get the facts, as there doesn't seem to be a comprehensive list of the specifications of each protocol.  I'm mostly interested in HUI and MCU, and I've read wildly varying reports on this forum about what makes up each protocol.  I don't mind midiOx-ing each one, but if it's already been done it would save me some time.  :)

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MBLC can only do "classic" Mackie Control. HUI is a different thing and as far as I know the protocol has never been published. I think some years ago someone wanted to reverse-engineer it and do a Midibox implementation (use the forum search) but I don't think there were any results.

S

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From a quick quick look at Serge's editor it seems that you can assign pitchbend to a fader which is 14 bits. Even if that's not exactly what you need, a few lines of code will certainly let you get the full 10bits to your DAW.
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