[sdiy] passive MIDI merge?

[J. Larry Hendry]

If you are willing to use MIDI thru to get to some of the MIDI INs of your
modules, and you are only worrying about the return to the synth for sysex
saving of patches, there is a very simple solution that I use that has no
active electronics.

My MIDI patch bay as 6 in and 8 out.  The 8 outs go to the first MIDI
devices down stream.  Most of those have a second MIDI device downstream via
the thru port of the first.  So, going only one thru port deep, you can have
16 devices.  Of course, they must be on different channels.

Now, when connecting the outs of the keyboards, you have to decide what you
want available full time to the interface.  Those will be "controllers."
Sysex for them is easy since you have a direct return.  On your modules, the
only time you need to use the out is for sysex patch storage.  This does not
need to be a full time connection.  I dedicated one of my patchbay inputs as
"sysex return" for modules.  I have a simple rotary selector switch, 2 pole,
12 position.  All modules MIDI outs run to this switch.  The switch feeds
the MIDI IN on my interface / patchbay.  So, for any modules I want to
sysex, I simple select its out to the MIDI in dedicated sysex return channel
with the passive rotary switch and it works fine.  If course, this would not
be good for real time controllers.  But, for the simple task of multiplying
the patchbay inputs for module sysex returns, this has never caused me any
trouble.  Essentially it is the same as selecting and hot connecting the
correct cable each time you need to sysex.

Larry Hendry

----- Original Message -----
From: Simon Gatrall <gatrall at pacbell.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Wednesday, October 31, 2001 5:24 PM
Subject: [sdiy] passive MIDI merge?


I have what I think should be a straight-forward MIDI problem, but I
can't find a good solution.  I have 13 MIDI devices in my studio and
one Opcode Studio 4 interface (8 in/out).  I'd like to ba able to
hook all of the external MIDI equipment to my computer with both the
MIDI in's and out's.  If I didn't care about sending MIDI back from
every device to the computer, I could hook everything up just fine
using the thru's that some of my equipment has.  However, I like to
be able to save patches and use the controllers on all of my gear,
not just selected pieces.  Given that problem, I can think of a few
options:

1) Buy another multiport MIDI interface (I just saw a used Studio 4 for
$150)
2) Buy a MIDI merge unit that can handle at least 6 inputs. (around $200
new)
3) Build my own simple MIDI merge unit.
4) Sell all my MIDI gear and go all [software/analog] (take your pick);)
5) Build/buy a MIDI patchbay.

I think there must be a simple solution for #3 because I don't need
an active merge.  There are two people at most in my studio at any
given point, and we aren't both playing/tweaking knobs at the same
instant.  Isn't there some simple way to combine MIDI signals if you
assume that no two pieces of gear will be transmitting at the same
time?  Does anyone have a schematic?

Solution #5 might also do the trick, but I'd prefer something that I
don't have to touch again.

-s!mon