[sdiy] passive MIDI merge?

[Theo]

Be aware it takes some care to make sure only one device is talking at the
time.
Active sensing (to check if the connection is still ok) and real time
messages (clock) are the main offenders.
Other culprits maybe odd things like the habit of the DX to sent sysex when
a programchange occurs,
or a unused keyboard sending all note off messages every now and then.

Theo


From: Scott Gravenhorst <music.maker at gte.net>

> If I understand what you want, This is fairly
> easy to do.  Each input port (more than one)
> and the output will have it's own socket connected to
> it's receiver (for inputs) and driver (for the output).  In
> between the receiver and the driver, the signal is at TTL
> logic levels.  You would wire the receiver outputs to the
> inputs of a TTL OR gate.  I think you can get gates with as
> many as 8 inputs.  They cascade if you need more.  The output
> of the OR gate then goes to the input of the driver.  As long
> as only one input device is 'talking' at a time, this will
> work just fine.  There are schematics on the web for the
> MIDI interface receiver and driver.  (I have it, if all else
> fails, email me and I'll send it).  This device will recieve
> MIDI on any of the inputs and route it to a single output
> socket.
>
> Simon Gatrall <gatrall at pacbell.net> wrote:
> >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
>
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