MIDIBox LC with 9th pot

[Lureks]

Hallo everyone,

In the beginning, sorry for my english.

I am interesting in building the clone of Mackie Control Universal. Almost identical is the MIDIBox LC, but there are 8 pots only. Is it possible a implementation of the 9-th pot (MASTER) in MIDIBox LC. If yes, what can I do this. Which additional elements are required and which changes are required in firmware?

Greetings

Lureks

[/tilted/]

The 9th pot is "not possible" because there is only 8 analog inputs on the PIC we use. The easiest way to do this is to use two cores for your master section. One core handles the first 8 faders, fader buttons and encoders/encoder buttons, The second core handles the master fader and all the control section buttons. This is what I (might) do on mine.

[Lureks]

Tilted, thnx for your answere.

I guess that your solution requires additional core with motorfaders controller connected to the host application through another independent MIDI port.

I want to build MIDIbox LC with 9th pot (MASTER) utilizing only one MIDI port (like Mackie Control). Is it possible at all? For example, implementation midibox-link in MIDIboc LC or another way: 2 cores with midi-merger or something different?

Greetings

Lureks

[doc]

Is it possible at all?

No.

Only 8 Faders per CORE possible.

and

Each CORE must have a dedicated Midi-Port for the LC.

You would win nothing by merging, because the 8th fader would work in parallel with the master-fader. Thats not what you want, or?

The ONLY possible way is to use 2 CORES and two Midi-Ports.

greets

Doc

[Screaming_Rabbit]

the 8th fader would work in parallel with the master-fader. Thats not what you want, or?

... are you shure about that?

I didn't try this but I think it would work with Sequoia... and some changes in the LC-Software

Greets, Roger

[/tilted/]

the 8th fader would work in parallel with the master-fader. Thats not what you want, or?

Nope.

Sorry, but the Way LC communicates is transmission/reception of Pitch Bend data.

As there is only one Pitch Bend control allowed per MIDI channel, each fader sends and responds on it's own channel.

Hence, on the Mackie unit, you have 9 faders. These use MIDI channels 1-9 on one midi port. The only reason we "can't" do that is the PIC we use has only 8 AIN ports.

Probably the confusion here is that the LC application has an option which selects which of the 8 available faders is to be the master (if any).

From LC App main.c

[tt]#define MOTORFADER0_IS_MASTERFADER 0 ; if set, the first motorfader acts as master fader[/tt]

The default value is 0, meaning there is no master fader.

So here's what you do:

Get two Cores.

First core does Faders 1-8 as channel faders.

Second core has one fader only (fader 1), selected as the master fader.

These two cores' outputs are merged into one port. Filter here so only one core will pass Sysex commands (for intitialisation call/response).

Their inputs are split from one port.

The host program will se one MCU, set up to have 9 faders, 9th fader as master. Only you will know the difference.

All this said, if you are good enough with the programming, and can find a spare I/O pin on your core, it might be possible to skip all this and do it all with one core. This would be a somewhat substatial re-write of the LC app.

[doc]

the 8th fader would work in parallel with the master-fader. Thats not what you want, or?

... are you shure about that?

Uuups.

You're right.

... next time I have to read a bit better...  :-\

( I thought you would like to merge 8 Fader + 7 Fader + master to a single Midi-Port... THAT wouldn't work..)

If you merge both Cores (with 8 + 1 Fader)  you'll need a strong Filter to seperate them. Thats also right and would work.

A side-question: Is this worth the effort (second Core, mf,  Merger, Filter ... ) just for one more fader (master) ?

I never used the master Fader of my mackie. For controlling the output I prefer BIG KNOB.

greets

Doc

[/tilted/]

I never used the master Fader of my mackie. For controlling the output I prefer BIG KNOB.

I agree.

Not the big knob specifically, but external analog control is better.

From an engineering perspective, you are much better setting your channel levels lower to avoid clipping, rather than overloading your master buss, then turning the master down.

If you turn down your master level below 0dBFS, you are essentially eating into your bit audio depth. Surely no-one wants that??!

[Screaming_Rabbit]

:o

I agree.

Not the big knob specifically, but external analog control is better.

From an engineering perspective, you are much better setting your channel levels lower to avoid clipping, rather than overloading your master buss, then turning the master down.

If you turn down your master level below 0dBFS, you are essentially eating into your bit audio depth. Surely no-one wants that??!

That's sounding pretty esoteric. :)  I think ADC, DAC, Bit-depth (fix/floating), internal gain structure, Master-Level and -Gain setting got mixed up a bit in this statement.

Greets, Roger

[/tilted/]

That's sounding pretty esoteric. :)

A little, perhaps.

It is probably a fair bet that any modern DAW program has enough calculation headroom to avoid clipping the internal mix buss in the digital realm. Here I agree.

By "enough calculation headroom", I mean that a signal which reaches your "master fader" at higher than 0dBFS can be reduced by the fader without clipping to below 0dBFS. This is ok, but a bad habit to get into, as this does not work the same in the analogue world.

My main point is that if you are doing you mix "in the box" and have no external monitor control system, but you do have a lovely shiny "master fader", it could be all too tempting to try to use your master fader as a monitor volume control.

Assuming that your DAW is feeding audio at absolutely optimised level (ie the highest level your DAW puts out to your soundcard is 0dBFS, then you should let it do so.

If you turn down your master fader to keep the neighbours happy, you will also be reducing your soundcard bit depth, because the master fader in a DAW is calculated before the DA conversion takes place. So assuming your gain structure is all good before the master (ie not clipping), and you turn down to say, -18dBFS at your master fader, you are basically chopping off 3 bits worth of data.

For every extra bit in your digital audio "word", you double the voltage resolution you can represent. (ie you get an extra 6dB).

At this point in the discussion, we usually get into matters relating to dithering and truncation, noise shaping etc. but we digress... A 9th pot should still be possible...

[Screaming_Rabbit]

Now I see what you tried to explain.

... the magic comment to understand was: "...tempting to try to use your master fader as a monitor volume control..." (though I don't know anybody doing this)

I mainly got confused by the statement "to set a fader to any dbFS" since you can't adjust a fader to FS. - dBFS refers to level and not to gain.

... confused me too:

Not the big knob specifically, but external analog control is better.

I'm not too good informed on semi-pro equipment anymore but I thought "Big Knob" is analog. Is it a Rotary controlling the Master-Fader? :o - I don't know.

How ever; I now understand what you mean and can agree.

Greets, Roger

PS: Thanks... no dithering etc. - That for I was reading books in the early days of digital technology. - Explaining facts not assumptions.

[/tilted/]

... confused me too:

I'm not too good informed on semi-pro equipment anymore but I thought "Big Knob" is analog. Is it a Rotary controlling the Master-Fader? :o - I don't know.

I really need to watch my phrasing... Yes the big knob is analog. I probably should have written:

Analog control is the better way, although I haven't tried the "big knob".

take care.