A MIDI board tutorial can be found at www.musicplayers.com.
A MIDI pedal board (also known as foot controller) is very useful together with rack effects. This goes especially for live use, but even in a studio you may want to bypass certain effects from time to time, or modify them in real-time with an expression pedal.
Agreed upon in the 1980s by instrument manufacturers, MIDI (Musical Instrument Digital Interface) is a standard for communication between electronic musical instruments. What is communicated is always instructions, not audio signals. The device that sends out MIDI information is called master while the recieving instrument is called slave.
Most MIDI capable products have one MIDI In jack for receiving and one MIDI Out for sending, sometimes also a MIDI Thru that simply passes along whatever entered MIDI In. In order to send signals between different units, cables with 5-pin DIN plugs are used.
Exactly which instructions a device can receive or send varies between products, and is stated in their MIDI implementation charts. The G-Force's MIDI implementation chart is found at the end of the manual. For the G-Force and a MIDI board/foot controller the supported MIDI instructions are (in normal language):
The G-Force can also send and recieve a bulk dump of all its User presets through MIDI, see the page on MIDI dump and SysEx file transfer.
A MIDI system can in theory send information on up to 16 separate "channels" simultaneously. By selecting the "Omni Off" mode and assigning different channels to different functions, these can be controlled independently of one another (for example, Channel 1 might be used for the G-Force while Channel 2 is used for say a MIDI preamp). You can also select "Omni On" in the Slave instrument making it respond to all 16 channels. The "MIDI Guidebook" (Roland, 1987) recommends that the power of the Master instrument is always turned on last, because it will then send out correct channel mode messages to the slave instruments. The same booklet also recommends turning off all power before making MIDI cable connections, in order to avoid false triggerings (this is perhaps mostly important when using synths and drum machines that may otherwise start making spontaneous sounds).
The MIDI pedal board/foot controller comparison table has been given its own page.
Most MIDI boards consist of a few footswitches and a display (or at least a few LED lights). Some also come with expression pedals, relays for amp channel switching and other features.
Foot switches should have a tactile feel so that you can tell if you have stepped hard enough on them. If you don't wear shoes while playing, certain types of switches may feel painful to step on.
The number of foot switches you need depends on how you plan to use the board. If you want to bypass effects, one switch for each effect block is the most convenient, plus up/down switches for preset changes and maybe one or two for the Tuner, Tap Tempo or other specialized uses. You may also be able to change the board's function so that each switch instead corresponds to a pre-determined preset. In that case you may need more switches, especially if you want to be able to recall a lot of presets at any time. Different boards may utilize their switches in different ways, for example one board may have many specialized switches while another is fully programmable. This means you can't always directly compare the number of switches on different boards.
Most MIDI boards have LEDs showing which switches have been depressed and a numerical display showing the selected preset number. If a digit in the display contains seven segments it can show any number between 0-9:
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but if it has only two segments it can only show the number "1" or nothing:
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This means that a "3-digit" numerical display may show either the numbers 00-199 or 000-999, depending on if the left-most digit features two or seven segments. Alpha-numerical displays contain even more segments and allow you to enter letters, words and whole preset names.
Note that the display only shows what you've selected on the board itself, which is not necessarily what's happening in the actual effect processor. For example, even if the G-Force remembers that you previously bypassed an effect in a preset, the board may not. To make the board understand what's really going on in the effect processor you may need a second MIDI cable from the effect and back to the board (see section G-Force Block status On/Off below).
An expression pedal (also known as a continous controller pedal) is recommended for real-time control of levels and other effect parameters. If the pedal is built into the board itself the amount of cables will be decreased, on the other hand it can't be moved away from the board's switches if you feel they are positioned too close. If a board does not have a pedal built into it you may still be able to connect one or more external expression pedals. Some foot controllers accept just about any external expression pedal, while others work best with certain models. This is due to the impedance of the potentiometer inside the pedal, a component that can easily be replaced if necessary. Note that unlike most other boards, DMC's old "Ground Control" works best with volume pedals (using 250kOhm impedance potentiometers). The newer "Ground Control Pro" board is more flexible (personal communication with DMC).
Some MIDI boards don't need a separate power cable, instead they can be phantom powered through the MIDI cable. Unfortunately there's no standard way of doing this. Some boards use ordinary 5-pin DIN contacts, other boards can accept 7-pin (Ernst, Lexicon, Rocktron) or even 8-pin (Peavey) DIN plugs (see also the page on audio electronics, and the comparison table). A cable with a 5-pin DIN plug will still fit into a DIN contact with 7 or 8 holes, though, in which case the extra holes (and the phantom power feature) are not used. DMC says that its "Ground Control" MIDI board can be phantom powered from either 5-pin or 7-pin cables (personal communication with DMC).
In order to get the phantom power into the MIDI cable, some effect processors (not the G-Force) send power out through their MIDI Out jacks. There are also adapter MIDI cables available on the market for boards using a MIDI In DIN jack with 7 holes. At least Rocktron makes one, where one end is split into a 5-pin DIN plug for the effect processor and a connector to a power supply, while the other end consists of a 7-pin DIN plug for the MIDI board. For boards that have jacks for 5-pin or 8-pin plugs there are (to my knowledge) no adapter cables available, but they should be relatively easy to make.
Some boards feature one or more relay outputs to control preamps that lack MIDI, thus eliminating the need for ordinary amp footswitches. If a board lacks a relay output you may still use it together with a MIDI patchbay, a gadget that lets you rout and/or bypass effects that lack MIDI support. A MIDI patchbay plus a foot controller usually become more expensive than a foot controller with a relay, but it's more flexible and you need one cable less on the floor.
Since the board and the preamp are usually located at different places you must still connect an additional cable from the board to the amp. A more practical solution could be to utilize unused pins in the MIDI cable for transmitting the amp relay signals, then you only need one MIDI cable from the board to the effect processor. From the effect processor's end of the MIDI cable you may then split off a branch that continues to the preamp (Vagn R. Nissen gets credits for this idea).
Some older MIDI boards may deliberately mute the signal during preset changes, possibly because older MIDI board processors couldn't keep up otherwise. The same might happen if you're using the switches of a floor multieffect as a foot controller. Some MIDI boards have controls where you can adjust the mute time. To make sure it's the MIDI board that causes the muting, try a preset change using the G-Force's front panel buttons and see if that works better. If the signal is still muted during preset changes the cause might be something else, for example that you have enabled the G-Force's Effect Muting feature in Utility > Config (software version 1.12 and higher). See also the page on seamless preset change and effect spillover.
Block status On/Off is a feature included from software version 1.13 that will send out the G-Force's block status (i.e. if an effect block is bypassed or not) at preset changes, in case your board cannot check this by itself. An extra MIDI cable from the G-Force MIDI Out to the MIDI board's MIDI In is needed. See the manual addendum for more details.
This feature from software version 1.13 seems to allow the G-Force to re-transmit and re-map a MIDI program change through its MIDI Out jack (in contrast to the MIDI Thru, which always sends out a copy of an incoming MIDI message). See the manual addendum for more details.
The G-Force is pre-programmed to easily recognize a number of MIDI board models, which are listed in the manual (other models usually work too, but you may have to do some programming yourself). From software version 1.12 the list is partially extended; here's the list given in the version 2.04 Manual Addendum:
Copyright © 1999-2016 Christian Jacobsson.