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Old 02-05-2021, 02:11 AM   #1
Jennifer
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Default Two computers into one synth unit alternately

Hi folks

The background is...

I've got an older Mac with Cubase, and a newer Mac with Reaper, and a few old hardware synth units.

I'm in the process of importing some of my old Cubase songs & ideas onto Reaper, so as to phase out using Cubase.

What would be ideal is if both computers could be plugged into the same set of synth units, and I could easily alternate which computer I'm working from. This would greatly assist being able to do A/B comparisons of the old & new versions of the songs, to make sure that the new version actually is sounding the same.

One way I could create this setup is with a switch box such as this:
https://mindburner-midi-products.my-..._18705228.aspx
with the computers on A & B, and a synth unit on C.

The only down side of that, as far as I can see, is that every time I switched playback between the old & new songs, I'd have to manually switch the switch. I'm already doing this when I go between computers because they're sharing a monitor and keyboard. This would bring it up to 3 manual switches - one for the monitor & keyboard, plus two MIDI outputs coming from each Mac. If possible, I'd rather not have to switch 3 switches every time I want to go back & forth between song instances.

Another possibility is, I think I remember seeing that there are also signal-manipulation boxes which can merge two MIDI signals, i.e. take the input from both computers and pass both on to the synth box. But i.i.u.c. those would tend to cost more, because they're more electronically complex. And also they need a power supply - more cables, more elements to potentially go wrong.

Then I got curious.

If I never have both computers simultaneously playing back, do I really need to have the two signals explicitly switched or merged at all? Is it possible to have a passive joiner-box which simply passes on all MIDI signals from both computers? and then it's up to me to ensure _not_ to confusingly send a signal from both at the same time?

This is where my MIDI knowledge runs out!

I'm not sure whether, when it's not playing back, each computer is also sending intermittent pings in the meantime, like saying "hello I'm still here" to the synth unit. If that does happen, then the intentional MIDI note (from the computer which was in the middle of playing back a song) might accidentally arrive at the same time as a "ping" from the "dormant" computer, and the playback might get confused.

That in itself seems like a yes/no question, though my search skills haven't yet presented the answer :-)

As a follow-on to that... if a passive joiner-box _would_ do the job, what would that likely be called, so I can search for it?

Also open to advice about alternative solutions.

Thanks in advance!
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Old 02-05-2021, 04:04 AM   #2
sonicowl
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I would recommend a box with a switch.

I don't think midi is "silent" even if you don't use it, unless you turn one source off. No way you can just join two signals together, it will be all scrambled. But if you turn one off, making it completely zero, then the other could work.

With audio signals, if you connect two output signals, each output would be loaded with another output, thus overloading it. Not sure how your midi outputs would behave, but could be the same problem, it is electricity after all.

You could connect two outputs into one, using resistors, like in audio. That would result in 6db drop in midi signal level, do there could be problem for synths getting too low voltage.

You could join two lines passively with 1+1:1transformer, that would be without loss. But any signal on the other line would scramble signal.

If you don't use them both at the same time, simple box with two inputs and one output, and a DPDT switch will work fine to switch between both lines.
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Old 02-05-2021, 06:08 AM   #3
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The only interfaces which - to my knowledge - allow to have 2 machines connected at the same time are the iConnectivity MIO models. Not exactly cheap though.
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Old 02-05-2021, 08:03 AM   #4
Hermani
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Hi,

I think you can solve it by just routing all the Midi via your newest Mac?

So old Mac sends all midi to new Mac.
New mac forwards all midi from old mac to synts.
( and it can still send its own midi )

I'm a windows user and use LoopMidi & MidiOX, for routing Midi , I'm sure similar tools exist for mac.
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Old 02-08-2021, 12:36 AM   #5
Jennifer
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Thanks everyone! Hmmm quite a lot of different options there.

<i>I don't think midi is "silent" even if you don't use it, unless you turn one source off.</i>

I must admit I'm still curious about the details of this. Does anyone know exactly what signal it sends while it's not playing back, and why?
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Old 02-08-2021, 06:57 AM   #6
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Hi,
What Hermani said.
Been doing it this way for years.
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Old 02-08-2021, 01:16 PM   #7
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Quote:
Originally Posted by Jennifer View Post
Thanks everyone! Hmmm quite a lot of different options there.

<i>I don't think midi is "silent" even if you don't use it, unless you turn one source off.</i>

I must admit I'm still curious about the details of this. Does anyone know exactly what signal it sends while it's not playing back, and why?
Potentially, Active Sense - I dunno how common that would be.
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Old 02-08-2021, 07:12 PM   #8
domzy
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do you have network ports on both computers?

some sort of network MIDI, such as copperLAN would save the need for additional hardware

http://www.copperlan.org/index.php/c...-for-end-users
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Old 02-09-2021, 02:27 AM   #9
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Quote:
Originally Posted by Jennifer View Post
Thanks everyone! Hmmm quite a lot of different options there.

<i>I don't think midi is "silent" even if you don't use it, unless you turn one source off.</i>

I must admit I'm still curious about the details of this. Does anyone know exactly what signal it sends while it's not playing back, and why?
Here is something, to see what you are dealing with:
https://www.youtube.com/watch?v=9enveiI0eg4
and
https://sites.ualberta.ca/~delliott/...g_MIDI_Out.pdf
+
https://forum.arduino.cc/index.php?topic=542807.0

Last edited by sonicowl; 02-09-2021 at 02:33 AM.
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Old 02-09-2021, 10:51 AM   #10
jrk
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midi "on the wire" is actually a (5mA) current loop. There's always scope for funny goings-on if you connect 2 outputs together at an input. If you don't want to switch, then you'll really be wanting a merge box. They're not wildly expensive (£75 for a Kenton).
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Old 02-12-2021, 03:35 AM   #11
Jennifer
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@jrk & sonicowl - Aaah this makes sense.

Thanks all, I learnt things from this thread!
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