Pedalboard patchbay/connection box with midi thru

[johanguitarist]

Hello!

I have built a passive patchbay/connection box for my guitar pedalboard in an aluminum box which works great. This is the schematic I used: http://stinkfoot.se/archives/1184
I would now like to add a passive midi thru connection to this, so I can easily connect the midi cable from my pedalboard to my Kemper. Basically the same as this one: https://shop.thegigrig.com/midi-cinco-patch-bay/

I am wondering how I should connect/not connect the ground from the midi jack(s) to the same grounding as the other jacks are connected to in the box? The midi jacks are have a metal casing.

Thanks! /Johan


   

[anotherjim]

Good question.
The "real" midi output driving the thru box has to provide cable ground connection. This is purely for screening since midi doesn't actually use the ground for signalling (but some simple devices that can get power over midi would need that ground for power return). Midi inputs should be isolated from ground so it doesn't cause a ground loop with devices that also share audio connections.
Although a thru box has a midi input, it's all an extension of the connected output it's running off, so ground connections should also go through to all the outputs - but only via the midi cables, not to the power or audio ground of whatever contains the thru circuit.

[johanguitarist]

Thanks for thorough information anotherjim.

I just checked the midi jacks I bought and they have 7pins and one pin connected to the metal housing , but I am not planning to run anything that need power through this box. This is the type that I got: https://www.google.no/search?q=REAN+NYS+326&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjfwovmiYzfAhUyqYsKHUDtAiAQ_AUIDigB&biw=1280&bih=667#imgrc=IgMrRQbfUilcsM:[/img]]

So have I understood you right that I only connect the 7 pins, and leave the pin to the metal housing unconnected?

[anotherjim]

There already is a MIDI standard for wiring TRS jacks to 5pin DIN, it might make sense to use it. Although the only choice is which of tip or ring goes to which of the DIN pins 4 or 5. It don't really matter which as long as you are 100% consistent with it.

If the DIN socket has 7 pins, 2 are probably both connected to the "shell" contact around the 5pin plug. They need connecting to the Shield pin2 on both inputs and outputs, since it can't be certain that the shell is connected to shield in the cable itself.

[johanguitarist]

Sorry I dont know what you mean. This is not about connecting from 7pin din to TRS. I want to connect 7pin din to 7 pin din. Straight through, nothing else.

[anotherjim]

I thought it was a passive patchbay thru you wanted? Midi patchbays often use TRS jacks for patching between 5pin din connectors. That way you can use the same patch cords and switched TRS sockets as for balanced audio patching.

Why have you got 7pin din for midi? Or do you mean the connectors you have are 5pin but with 7pins on them?

If so I explained above what the 2 extra pins at the front do.

To connect a midi socket to another midi socket, you wire them pin for pin. Pin 1 to pin1 etc. You can wire more than 2 sockets together, but it can't drive more than one device at a time without active circuity in between.

[johanguitarist]

Hi

Yeah I think we misunderstood each other. All I want to do is to be able to plug in a 5pin midi cable on one end of the box, and another 5pin midi cable on the other side of the box.

This box is only meant to make it easier to connect the necessary cables from my pedalboard (where this box is) to my amp and other effects. The box has several TS connections to route audio in and out of the board, but I also want to connect a midi cable.

The reason why I got 7pin din sockets was because that was all I could get hold of at the time. The TS sockets are made of plastic, but grounded to the metal chassis of the box from one of the TS inputs.

So back to my original question: How do I wire the midi sockets? Just from pin to pin, and thats it?

Thanks!   

[anotherjim]

Yes, direct one to one wiring. Pins 1 & 3 are optional. Pins 2,4 & 5 are the ones that matter. 4 & 5 should be a twisted pair - I would use a piece of "twin & screen" hook-up cable like this...
https://www.canford.co.uk/Products/31-001_CANFORD-FST-CABLE-1-pair-Black
, but if the connectors are really close, individual wires will be ok.

[PRR]

The MIDI interface was DESIGNED to not fook-up your precious Audio Ground. The data runs current-loop, not voltage level, using only pins 4 and 5. The data is grounded at the source; at the destination is only a floating opto-coupler. There is a plug shell, and often a cable shield; these are not essential for MIDI data but bonding them to audio common "may" reduce MIDI-bleed into audio.

For most situations, I would just wire pins 4 and 5, ignore all else.