OK, I’ll try to summarize what the ProBox is. But I better start out with a summary of how the D8B differs from the concept of a “regular” mixer for this to make more sense.
On a conventional/analog mixing desk, the signal “physically” (or rather electrically) travels from the top (Pre-Amp) to bottom (Pan+Fader) of each of the vertical (and often individually removable / modular) channels on a mixing desk, before being summed with other channels or sent to specific outputs (depending on the purpose).
On the D8B (and most other digital mixers), the “vertical channels” are represented by lines that are printed on the surface of the mixing desk, to give it the familiar look and function of a “conventional” mixing desk, but that’s not really what happens on the inside of the D8B at all.
While the “concept” of how the audio signal travels through individual channels within the D8B is the same as on a conventional/analog mixer, what’s actually going on on the inside is quite different.
Invisible to the user, the channels the D8B has, aren’t “physically” present beneath the vertical “printed on” mixer channels. Instead, the components the (digital) audio signal travels through, are located on various circuit boards throughout the the D8B console and rack unit, that are separated “by function.” Not by physical/visible vertical channel.
Where I’m getting at with all this, is that there is no 1:1 correlation between the channels and their controls that are printed on the SURFACE of the mixing desk, and what the desk is doing on the inside.
Instead, nearly all of the buttons, knobs and faders on the D8B, only send MIDI Messages (similar to a MIDI controller keyboard) when actuated. The “insides” of the mixer then translate that MIDI message into the function that button/knob/fader is supposed to perform.
In other words, there’s a “layer of abstraction” between taking an action on a physical control on the mixer, and the mixer “translating” that into an actual “electrical” action.
In fact, you’re dealing with that layer of abstraction (or rather 4 to 5 of them), when switching between the Mic/Line, Tape, Effects, Masters and HUI layers on the D8B in regular use.
The buttons and knobs technically “send the same message” when on different layers, but the mixing desk knows to interpret what the MIDI message that control has transmitted in context… that’s why, for example, the same fader controls an FX return on one layer, while it controls the level on an input channel on another layer.
The “fifth” layer on the D8B (that is only available if you have Mackie OS 5.1 installed), is the “HUI” layer. The HUI, or spelled out “Human User Interface” is another Mackie hardware product, that was designed to connect to DAW computers, and remotely control DAW functions from it. A single, physical HUI unit, can control 8 DAW channels at the same time (but you can bank over to see more channels).
Since the Mackie OS 5.1 update, the D8B has “one” HUI unit already built in, but it has to be activated (e.g. from a menu on the monitor or via buttons on the D8B, itself). You can then access the HUI “layer” by pressing Shift+Masters together, to quickly switch to HUI mode, just like you’d switch between the Mic/Line and Tape layers on the D8B.
So, in HUI mode, the D8B knobs and buttons still send the same MIDI information, but the “insides” of the D8B translate that into the “regular” HUI protocol that many DAWs understand. So, essentially, adding the HUI layer in Mackie OS 5.1, was like adding another “language” what the buttons and knobs send, can get translated to, and sent to your DAW to remote-control it.
So much for the D8B and how the buttons and other controls work, to control different functions, when on different “hardware abstraction layers."
The ProBox is a hardware device, that technically does more or less EXACTLY the same thing as what the D8B with OS 5.1 already does when in HUI mode. It translates what the buttons and other controls on the D8B are doing, and sends the translated MIDI info to your DAW (and also some feedback back to the D8B, to show the button status and show LED meters, etc.).
However, the ProBox emulates 3 (!!) such HUI controllers at the same time - or alternatively, another Mackie DAW controller system, called the “Mackie Control Universal” and two extenders for it).
Or in other words, the D8B’s built in HUI mode makes use of only 8 of the faders on the D8B, to simultaneously control up to (only) 8 DAW channels in your computer.
The ProBox emulates 3 (!!) HUI or MCU devices at the same time, and by doing so, it allows you to use ALL the faders and knobs on the D8B simultaneously, to control 24 DAW channels in your computer at the same time.
You can select via the built-in display on the D8B, if the ProBox runs in HUI or MCU mode.
One main difference between the HUI and MCU emulations is, that the HUI protocol does NOT support a Master Fader. The MCU protocol does. So, when in HUI mode via the ProBox, the master fader has no function. When in MCU mode, the master fader controls the master fader in your DAW. (The button layout is also completely different - just how it’s different between a “real” HUI and a “real” MCU system).
So, to summarize what the ProBox does, that the D8B itself can’t:
The ProBox lets you use the D8B as a MIDI Controller, to simultaneously control 24 DAW channels at the same time. (The D8B itself can only do 8 at the same time, and only if you have the Mackie OS version 5.1 installed).
Another important aspect of the ProBox is, that D8B mixing systems that fail to boot as intended and are more or less “dead” as a mixer, can usually still be used with a ProBox as a 24-Channel DAW controller.
So if, for example, your D8B gives Error 43 when attempting to start it, instead of trying to fix that or throwing the D8B in the trash, you can get a ProBox and use the D8B console to control your DAW.
When using an otherwise “dead” D8B this way, you will NOT be able to pass audio through the “mixer channels” of the D8B - because that part of the D8B might as well be dead, when used this way.
In other words, the ProBox doesn’t magically “fix” the mixer functionality in an otherwise “broken” D8B. It just adds new/different functionality (DAW control for 24-channels. Passing audio channels through the D8B is an entirely different thing, and NOT something the ProBox supports.
The ProBox does allow you to use “some” of the audio functionality on the D8B - but NOT and NEVER-EVER any “channel” audio from the 24 channels+faders (or even multiple layers of them).
The audio functionality that still works when using the D8B with the ProBox, is very similar to yet another Mackie hardware device, the “Big Knob.”
The Big Knob is a monitor controller, and the D8B in ProBox mode can still do more or less what the Big Knob does (so, it doesn’t “mix” anything… it just routes mostly the “2-Track” input signals, to dedicated speaker+headphone output jacks).
So, you can connect a couple of pairs of speakers to the D8Bs Nearfield and Main Monitor outputs as you normally would in mixer mode, as well as connect headphones, and then feed stereo-audio signals into the 2-Track A, 2-Track B and 2-Track C inputs. Then use the buttons in the monitor section of the D8B, to send these input signals to your connected speaker pairs or headphones.
There is a way to get a couple of additional signals in - I think via the Aux 9-10 and Aux 11-12 OUTPUTS on the D8B - where you connect a signal SOURCE to said OUTPUTS on the D8B - which sounds like it’s completely wrong… and at least the impedance is a total mismatch (so, your signal will be very quiet), but by sort of “misusing” that analog circuit in the “wrong direction,” you can connect 2 more stereo audio sources that you can route to the speakers or headphones (details for this are in the ProBox manual).
To reiterate - there is ABSOLUTELY NO mixing functionality on the D8B when using it with a ProBox. But you do get “Monitor Controller” functionality, but the only thing that you can do here, is to route a particular input, to a particular output (2-Track inputs and/or some of the Auxes to Speaker/Headphone outputs… nothing else. No signals will be “mixed” with any other signals).
And to make this even more clear, for those who may be reading along, but still don’t get the message:
The ProBox will NOT let you route 24 (or even more, and also not fewer, either) audio channels between your DAW computer and the D8B console. Making that work, requires a fully working D8B mixing desk with at least 3 I/O expansion cards in the D8B (ideally digital, such as 3x ADAT cards), as well as an audio-interface (or multiple cascaded ones) that provide 24 matching inputs and outputs (e.g. matching digital I/O via ADAT) that you can connect the D8B extension cards to.
The ProBox is NOT a shortcut to achieve this and will NOT route any audio channels between your computer and the D8B.
In fact, a shortcut to achieve this DOES NOT EXIST. Even today, an audio interface for your DAW computer that would give you the I/O needed to interface with the D8B in this way, would set you back at least $1,000, plus a lot of dedicated wiring… and you have to have a fast and modern computer for this, as well. There are a few audio interfaces with 24 digital I/O channels… but not usually USB 1.1 (like the ProBox), but rather Thunderbolt or at least USB-C (i.e. much higher bandwidth)… and even USB-C devices still have relatively high latency, IMO. I wouldn’t base a HUGE setup like this on a silly USB audio interface. Again, there is NO shortcut for this, sorry.
Having said all of this - if you have a fully working D8B, that you can use as a mixer, you can ADD a ProBox to expand the D8B’s functionality (i.e. 24 channels of DAW control instead of 8), but you can really only use the D8B EITHER as a mixer, OR with the ProBox, per session. It’s not designed to allow you to pass audio through the D8B’s mixer channels, while using it with the ProBox as a DAW controller.
The reason is, because one of the two connectors on the ProBox (the other being a USB connector that goes to your DAW computer) needs to be connected to the “Console Data” DB25 jack in the back of the D8B console. That’s where you’d normally connect a DB25 cable between the D8B rack unit and console. So, by interrupting that to connect the ProBox, the D8B will no longer work in mixer mode.
You do have the option to add an external switch-box, so you can run the D8B as a mixer for some sessions, or as a 24-channel controller for other sessions, without having to physically change the connections every time.
Please see the pictures below. The yellow thing is a ProBox (resting on one of my D8B spares in storage). The first pic shows the DB25 cable on the ProBox, connected to the “Console Data” jack in the back of the D8B. The USB cable that is attached to the ProBox, would then need to be connected to your DAW computer (here just shown resting on the DB25 connector).
Additionally, the BFC cable (the big round connector above the DB25 cable in the first pic) also needs to be connected between the D8B rack unit and Console - mainly to provide power to the components in the console. The rack unit otherwise doesn’t have to be able to boot up but needs to at least “turn on," and the D8B console doesn’t need to have ANY of the expansion cards to work, for it to work with the ProBox as a DAW controller).
The 2nd picture below, shows a parallel/serial switch from the front, and the 3rd pic shows it from the back. If you connect the ProBox DB25 connector to Port B of such a switch, and connect the DB25 cable from the rack unit of the D8B to Port A, while connecting the I/O jack in the back of that switch to the D8B console (hooked up wrong in the pic, sorry - the DB25 cable coming from the console should go to the I/O connector on the top, not Port B), you can do this:
Have the switch set to Port A, and fully boot the D8B as a mixer. Then, once fully booted as a mixer, you can switch to Port B and use the D8B as a DAW controller. If you’re LUCKY (but this doesn’t work every time), then the mixer portion of the D8B will still pass audio that is coming in through the mixer channels, while using the ProBox to control your DAW… but half the time when switching between Port A and B, some level faders will reset to -infinity (silent), or some routing gets changed… but if you really MUST have the D8B pass audio while using it with the ProBox as a controller, switching back and forth a few times (while fixing modified levels/routing every time), usually eventually works enough to pass the audio you need.
So, this is of course not a usable method in any professional environment. I’d suggest to use the D8B only as a mixer during some sessions, and only as a controller with ProBox during other sessions. But if it’s just you by yourself playing with this and don’t mind the hassle, you CAN actually have both more or less “working” at the same time.
For context, I’m adding a pic of where that parallel/serial type of switch is located in my setup (below the console-furniture). The other beige thing to the right of that, is a vintage KVM switch that supports PS/2 and AT-Keyboard connectors (the MIDI looking connectors). In my current setup, I’m using a D8B in mixer mode (with serial switch for ProBox), a Mackie HDR (which is based on the same computer components as the D8B rack unit), and a PC running Windows 98, that is based on D8B rack unit hardware, because I have an old ISA sound card in there to be able to still load songs of mine from 30+ years ago. This way, I only need one set of keyboard+mouse+monitor, to control these 3 “vintage” types of computers.
…and since there’s now not much else missing to illustrate a more or less “complete” D8B setup, the last pic shows my M-Audio “Digipatch” digital patchbay, and a little further below, there’s an UA Apollo 8 (single ADAT I/O) and PreSonus Quantum (dual ADAT I/O) audio interface.
So, this is the type of setup needed, if you want to have 24 channels of digital audio going from your DAW computer to the D8B and back, without adding any unnecessary conversions on the way. Using those two interfaces at the same time, allows me to use the 3x ADAT I/O ports between them, to connect to the 3x ADAT I/O cards on the D8B (…and I get the 8+8 analog I/O on these two interfaces “extra”).
The Digipatch digital patchbay has 6x ADAT I/O (and some extra RCA S/PDIF). I use this, to temporarily connect other ADAT capable devices to either the D8B or to one of the audio interfaces via ADAT - such as another 8-channel Mic Pre with ADAT output that I have if I want to record from them… that normally is patched to the Alt I/O cards, since I otherwise route my FX returns through there, etc.).
Unfortunately, that Digipatch doesn’t have enough ADAT ports so I could freely patch any ADAT port I have with any other - I had to make some compromises, and leave some ports “uncountable” - I’m having my eye out for either a Frontier Design Apache digital patchbay, or a Z-Sys digital detangle with the right set of ports in the back (i.e. lots of optical ports… I’ve seen them with up to 16 ADAT capable ports).
So, from what I’m aware, this is a sort of "fully expanded” D8B setup:
- Mixer fully working
- 24-channel audio integration with DAW via 24 digital I/O on D8B and audio interfaces
- Routable ADAT I/O in sets of 8 via digital patchbay
- Alternative 24-channel audio integration with HDR via TDIF (possible via 6x DIO-8 cards)
- 24-channel DAW control via ProBox (switchable with external switch).
Besides, I have a ADAT card in the Alt I/O slot (routable via digital patchbay), 3 UFX cards and an MFX card installed.
A lot of times when someone asks about the ProBox on here, I get the impression that they think that you can do ALL of this, simply by adding a ProBox. But again, that’s not the case, and I tried to go over the details of what works and what doesn’t, depending on what sort of expansions and interfaces you have available to you.
If it’s an “otherwise broken” D8B, a ProBox will “only” add 24-channel DAW “remote control” - but will not allow to have any audio transmitted between your DAW computer and the D8B. For that to be possible, some of the other “extras” I’m mentioning above are needed (e.g. expansion cards in the D8B, and an audio interface with enough I/O to connect all the expansion cards).
I hope this finally puts all the info in one place, and that this is useful to anybody looking into a ProBox (which munkustrap on this forum still builds by-hand, one-by-one, from what I understand… as a hobby).
- Pic 1 - ProBox to Console connection
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- Pic 2 - Serial/Parallel Switch (front)
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- Pic 3 - Serial/Parallel Switch (back - black cable should go to upper switch connector)
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- Pic 4 - Switch+KVM under desk
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- Pic 5 - Digital Patchbay and Audio Interfaces
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