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DIY switchable MIDI THRU Interface



When working on this gig-rig, I wanted to be able to make more use of the fact that I have two sound modules. It would enhance the music when I could more easily switch sounds during a song. I would then be able to play a different instrument sound for the melody than for the solo in a Jazz standard. The problem was that I never had enough time to make changes to the sound module, especially when you are expected to play the melody and the first solo.

Since I wasn't going to use the Emagic AMT8 USB MIDI interface anymore in the gig-rig, I would definitely need a MIDI Thru box to connect the MIDI OUT of the Kenton Wireless receiver to both sound modules. These are available from various companies, but can also, with a bit of knowledge about electronics, be made "Do It Yourself" style. I got the schematics for a MIDI THRU box from the internet. All MIDI devices that do something with the MIDI data need a microchip controlled design which needs programming as well. A MIDI TRHU box doesn't need that because it doesn't interfere with the MIDI data.

I also looked into standard available MIDI devices to do the switching; I would then need a MIDI THRU device along with a MIDI footswitch controller for each sound module that controls Note On/Off data and some standard foot switches. This solution is very fancy, but will cost much more.

I made some changes to the schematics where I added ports that will block MIDI data going to each of the four outputs. These ports are controlled by latch type switches as explained in the next part. Since this device doesn't control MIDI data, just blocks it from going to the sound module, it isn't completely idiot proof; when you block the MIDI data while data is sent to the sound module it will go on playing the data until it receives a Note Off signal again. You need to enable MIDI data again and stop playing for it to stop. For me it isn't a problem since I know and only press the switches when I don't generate sounding MIDI data.

The MIDI THRU device I made has a MIDI IN at the top (see picture) a 12V DC connector at the bottom, 4 MIDI THRU (OUT) at the left and opposite of that (at the right) 4 jack connectors where the foot switches are plugged in.
If you want to know how to build it and get the schematics, please send me an e-mail.

Behringer AB200 Dual A/B Foot Switch



The Behringer AB200 Dual A/B Foot Switch is a universal foot switch designed for switching all kinds of gear. It is mainly used by electric guitar players to switch one guitar to two amplifiers or two guitars to one amplifier on each channel (1 and 2). You can mechanically attach more of these switches together in a row.
Each channel of the device can be set, by a small sliding switch, to non-latch (switching contact On only during the time the foot switch is pressed) or latch (one tap on the foot switch switches it On and with the next tap it switches Off).
I use the foot switch to control the DIY 4 channel MIDI THRU box. Because the AB200 has latch circuitry built-in and uses relay type switches on the outputs, I could keep the design for the MIDI THRU box very basic. Each of the switches now switches the MIDI THRU of the first two channels of the box, to which both the VL70-m modules are connected, On and Off. This way I can block MIDI data going from the WX-5/Kenton to either one or both the MIDI modules, allowing me to keep my hands on the instrument while still being able to quickly change modules, thus sounds. I like this because now I'm able to play different sounds during a song.