Do passive Midi Through boxes work?

[SHall1000]

I have been using a Belkin Rock Star Headphone Splitter to link the midi out of a Beatstep Pro to a selection of Volcas and Roland Boutiques. With some combinations of gear this does not work with more than 2 devices attached. For example connecting a SE-02 causes the Volca sample to randomly trigger samples and start/stop the sequencer. This is reportedly due to a voltage drop when 3 devices are attached.

Does anyone have experience with non-powered midi thru boxes such as the Miditech Midi Thru/Filter or the MIDI Solutions Quadra Thru V2 in such a situation. Some report that these devices do not have the same issue but I am confused as to why they should work when they have no additional power supply.

Would like to avoid more power cables but keen not to waste £50 unnecessarily.

[lfm]

Sending side is supposed to drive a current through a optocoupler on receiving side.
If passive it is knicking power from what it received and at some point malfunctions.

But as one intermediate step like from a powered unit, chances are good it works.
Starting to do Y-connections, not so sure - you will try to drive optocouplers in parallell - a bit risk one will win and other fail.

And since sending side needs the same power driving receiving optocoupler the units become part of same circuitry - which optocoupler are there to prohibit.

[JCJR]

The basic circuit for a powered 1 to many midi y box is very simple if that is all it has to do. Just a wallwart and a few cheap chips and connectors in a small box.

Many of the midi solutions little midi power boxes are in genius. Having a low power microprocessor powered from the idle voltage on the midi out cable to do simple tasks. I have a few of em from long ago that generally worked good if not heavily stressed.

Maybe the newer ones can handle heavier loading with newer lower power processors, dunno.

Midi out idle state has 5 volts between the "high" signal wire and ground. During a message there is a short blip of "switch closures" to ground encoding the message. So if a midi stream is lightly loaded you have +5 volts available "most of the time". Schematic on this page:
https://www.tigoe.com/pcomp/code/commun ... AXoECAUQBQ

So a midi solutions box can charge a storage capacitor to run the little microcontroller and the capacitor stores up enough extra power to keep running the circuit in the rare times when the signal is toggling and you don't have steady DC.

For instance my ancient little midi merge works flawless on sparse streams but it messes up with dense streams. Maybe because it overruns the little microcontroller maybe a dense stream requires more current than a capacitor can store up in the idle times between messages.

So a dumb wallwart powered midi splitter would be more reliable and in principle ought to be cheap because of the low parts count, but if it doesn't sell enough to be a mass market item may be expensive because of rarity and lack of product price competition.

[lfm]

As long as midi out side of box does not use the same power as midi in side - all is good.
If it does - you create a huge ground loop through midi cables between all equipment as well as units having their signal ground other ways.

Midi in is basically a led normally, current in and out back to sender, and have no galvanic connection to midi out side of the same box.

I fear passive boxes violate this.

[JCJR]

I agree a midi splitter box should have optoisolated input and separate driver circuits for each output.

Maybe it would be possible to get a clean drive with a "bigger" single output driver transistor feeding multiple parallel sets of 220 ohm resistors and din jacks, but parts count would be so negligible either way,. And driving parallel from a single transistor might round off signal edges from stray cumulative inductance and capacitance, though the midi baud rate is very slow and should be forgiving.

IIRC a "good" ground loop avoiding midi cable would disconnect shield ground to plug shell though audio din cables with shield connected on both ends works ok sometimes then occasionally they cause ground loops depending on combinations of equipment.

A midi receiver that has isolated jack floating on a circuit board and no ground connection in the jack to the circuit board or chassis wouldn't care about the midi cable's shield ground wiring.

[SHall1000]

Thanks for the technical enlightenment guys but does anyone out there have any practical experience of using either a Miditech Midi Thru/Filter 4 or the MIDI Solutions Quadra Thru V2 with a Beatstep pro and three or more Korg Volcas or Roland Boutiques. Any reports of successes or failures appreciated.

[jarekmn]

It is the old thread but new problem for me. MIDI Solutions have got detailed FAQ page. It explains a lot if not everything. As your BeatStep as my Emu XMIDI USB/MIDI adapters are voltage dead unfortunately. They don’t provide any voltage, any current flows from MIDI OUT. As MIDI Solutions have really genius passive devices, so the other source MIDI devices, synths etc must be active MIDI devices.

[mztk]

have both quadra thru v1 and v2, never noticed a problem, brilliant little boxes.

[psycho45039]

The Kenton Thru-5 is powered and I have had no issues with it. I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

[mztk]

I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

depends on the MIDI Out feeding it. some don't provide the current (? power?)

[psycho45039]

I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

depends on the MIDI Out feeding it. some don't provide the current (? power?)

Yes, you need to be careful about it. It almost seems to be incompatible with more things than what it is compatible with. See the list at the bottom of this page. There are many more that aren't on the list that also don't work. My advice would be to avoid this product for this reason.

https://www.midisolutions.com/faqs.htm#Power

[vitocorleone123]

I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

depends on the MIDI Out feeding it. some don't provide the current (? power?)

Yes, you need to be careful about it. It almost seems to be incompatible with more things than what it is compatible with. See the list at the bottom of this page. There are many more that aren't on the list that also don't work. My advice would be to avoid this product for this reason.

https://www.midisolutions.com/faqs.htm#Power

Yep. Kenton MIDI boxes take power but they simply work.

[mztk]

I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

depends on the MIDI Out feeding it. some don't provide the current (? power?)

Yes, you need to be careful about it. It almost seems to be incompatible with more things than what it is compatible with. See the list at the bottom of this page. There are many more that aren't on the list that also don't work. My advice would be to avoid this product for this reason.

https://www.midisolutions.com/faqs.htm#Power

Yep. Kenton MIDI boxes take power but they simply work.

so does the MIDISolutions QuadraThru (and QuadraMerge) - especially in a space-conscious mini setup with volcas etc. where you want to keep cables and power supplies under control. i think in most situations they will work. i haven't encountered problems in simple use, and find it very liberating to just be able to plug MIDI cables in. i'd say it's worth giving it a try.
if in doubt, get the V2.

edit: just read that MIDI Solutions FAQ. quite a long list of devices reported not to work, but not killer IMO

[vitocorleone123]

I also have a MIDI Solutions Quadra Thru and it is hit or miss as far as working with MIDI devices.

depends on the MIDI Out feeding it. some don't provide the current (? power?)

Yes, you need to be careful about it. It almost seems to be incompatible with more things than what it is compatible with. See the list at the bottom of this page. There are many more that aren't on the list that also don't work. My advice would be to avoid this product for this reason.

https://www.midisolutions.com/faqs.htm#Power

Yep. Kenton MIDI boxes take power but they simply work.

so does the MIDISolutions QuadraThru (and QuadraMerge) - especially in a space-conscious mini setup with volcas etc. where you want to keep cables and power supplies under control. i think in most situations they will work. i haven't encountered problems in simple use, and find it very liberating to just be able to plug MIDI cables in. i'd say it's worth giving it a try.
if in doubt, get the V2.

edit: just read that MIDI Solutions FAQ. quite a long list of devices reported not to work, but not killer IMO

Easier and less stressful to just get a Kenton and go about your day without ever worrying about it again. But not everyone approaches things that way, I know. Personally, I’d rather pay a little more to do it right than perhaps save to do it for less… or have to deal with it again because it isn’t working right.

The new Erica Syntjs Thru looks great.