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FR-4xb, FC-300 and BK-7m notes


Sep 18, 2019
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I researched this quite a bit while waiting for my FR-4xb to arrive. I wanted as clean and compact of a way to connect the FR-4xb, BK-7m and FC-300 foot pedalboard as possible, and after reading as much information as I could find, I think I found a slightly different approach that so far has been working perfectly for me.

You need a USB MIDI Host adapter, so that it plugs into the USB port on the accordion and converts it to MIDI DIN plugs
This unit works very well, and is quite a bit cheaper than the Kenton USB MIDI Host box:

I have seen other boxes around, but cant vouch for how well they would work, especially handling the SYSEX messages that the FC-300 sends, as some MIDI interfaces seem to have problems with those.

By connecting the USB MIDI Host adapter to the FR-4xb via the USB connector, it provides both a MIDI IN and MIDI OUT at the same time. All the cables I picked up (including a short USB extension and audio cables) have right-angle plugs, so they are lower profile connections than you have with a MIDI DIN cable plugged into the FR-4xb.

I had to change the USB Drv setting on the FR-4xb to GEN. And you have to power off the unit for this to take effect. Before doing this, the converter box I used would not see the FR-4xb.

The USB cable goes from the FR-4xb to this box, and then a MIDI DIN cable goes from the output of this box to the input of the BK-7m, and another MIDI DIN cable goes from the output of the FC-300 to the input of this adapter box.

If I dont want to worry about a separate amp (depending on where I might play), I can route the audio output from the BK-7m to the input of the FR-4xb. For this I used a small right-angle extension to go from the 3.5mm connection on the FR-4xb to a 1/4 female TRS connector. Then I inserted a mono (what is coming from the BK-7m) to stereo (what goes into the FR-4xb) adapter so the sound comes out of both the bass and treble sides. I could have used a stereo cable, split at the BK-7m with two mono plugs to a stereo going into the FR-4xb, but there are a lot of options for how to do the audio cabling.

If I do want to use a separate amp, I just remove my extension cable and plug the right-angle mono 1/4 plug into the FR-4xb output and route that into the BK-7m audio in plug, and then connect the BK-7m output to the external amp.

All in all, I think it was very economical and provided the clean look I was trying to achieve with right angle connections, minimal cabling, and giving a connection to both the BK-7m and FC-300.

I hope someone finds this useful.

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