Power over Midi?

Those units should be forbidden!

They drain power formt he Midi line wich is not allowed based on the official Midi specs.

This might not be problematic based on your setup, but it immediately can and potentially can create all sort of issues from partial or fully not working midi-data transmission to ground-hum and other obscurities.

I HIGHLY recommend using midi-devices such those from Kenton that require a power-supply.

Good to know in case of trouble. I haven’t had any of those issues with my Quadra and:

  • TR8s
  • TD3, RD6
  • MD, MNM, OT

I am using power bricks most of the time, a nice Sabrent USB switch for Mac comms and Anker USB power when needed, so generally premium stuff.

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yes it’s absolutely possible that this works fine.

but even simple setup changes can cause issues. I would recommend everyone to stay on the safe side and use devices that match the midi specs.

For example a Kenton midi thru costs in Germany 1€ less then those Midi Solutions devices

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I would generally agree, but the current requirement of ICs today is dramatically less than in the early ‘80s. So there should be a massive surplus of current. The Quadra may draw less current than is lost through long cables.

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I have 2 midi thru (2 out) and 1 quadra thru, I’ve never had any issue. I also have a midi solutions footswitch controller which does require power. It seems like they know which devices require a power supply, and which ones midi spec can provide power for.

Do you also think phantom power over XLR is a problem? it’s certainly higher voltage, but the concept is the same. Am I incorrect?

Very detailed information available on this page if anyone is interested in specifically why midi solutions does not offer an option for both the power supply and power over midi on the same device:


you state the what the company says about their products, as proove that those products must be good?
No further comment on that.

XLR has 3 lanes, while 2 are maximum needed for audio-connection of a mic. The third one is free for power. And the power gets particularly for that use - to power a mic - injected.
Using that as an argument shows that you didn’t understand anything about the power on a midi-line. The power is there for the opto-couplers. For nothing else.

And once again what i already very clearly said:
Using the power for those thru-boxes might work without any issues. But the chances are there that it doesn’t work at some point. If you are happy with that . Fine for you.
It just should be said when those devices get recommended.

It has been fine for me? XLR has audio, the signal passes differently to a midi signal. But it grounds, powers, and passes signal on the same cable. You seem to have had some personal issues with midi cables or power via midi, what happened to your equipment, did it fail by using this design?

I’m not against you, it’s great if the products work for you. I do understand it sounds comfortable to not have to use another PSU.

But as i said : It might work. You are free to say that it works for you . My point was only - and i really don’t understand, what part i didn’t communicate clear enough - that it suddenly might not work anymore. And I think those products cannot be recommended without clearly mentioning the potential problems they can bring.

I personally have no problems with those boxes, as i don’t use them. But i understand that products that are not conform with tech specs might cause issues. It’s very simple… you take some amount of power from a part that requires it. What do you expect will happen to that part if it doesn’t get enough power anymore?

The problems that can occur are typically partially/fully not transmitted midi-data and/or ground-hum.
The problem with that is, that it might not be obvious until it gets too much or adds up.

You’re correct that the midi latency (if that were an issue) might take a lot of poking around to determine if the thru / merger was the source, but for my understanding unless your power source is from a battery there is only a voltage cap on the power that comes through midi - what I mean is the old protocol was 5v, new midi protocol only passes 3.3v - so unless there is a failure in the first device in line (passing the power over midi) then the only thing to stop the midi power delivery would be a bad cable. However, a bad cable will create a problem regardless of any splitting or merging of signals, also a problem within the midi throughput of the first device (the one to pass midi) won’t receive any compensation in the degradation of signal simply because the split is optoisolated and provides it’s own power.

I understand conceptually, just midi alone can have problems from the conditions you’re stating, even with no peripherals attached. By that logic any parasitic loss can amplify the issues, that much is clear, but it would be just as likely for the problem to be present with or without the midi solutions product. The biggest issue using the products from a functional standpoint would be if the center pin is not grounded to the power return pin in which case no power would pass at all, or if the signal were not powerful enough to power the older midi solutions product - one of my thru boxes is like this, it requires the 5v midi (4v in actuality to function) so I got a newer multivoltage and it works well for newer protocol gear. Kenton makes fine product, I have no issue with that but I’m trying to understand where you have experienced an issue with midi solutions or even any midi powered products? Older M audio (midiman) had some gear that used the same principal, so this isn’t a new technology to take power over midi. I also understand you aren’t saying you have a personal agenda against the type of parasitic power, you’re stating as a precaution - but as a precaution, should someone say for every power supply unit driven product that if the power supply has a bad transformer and a surge of power is sent through the device it can be fried, or at a minimum the large capacitor which regulates throughput power before any voltage is delivered to your equipment may pop and then it will develop signal path noise or possibly failure of equipment? There is a possibility for this to happen. It seemed like you must have had an issue with the type of midi powered product because there are possible issues even with standard transformer regulated power supplies, my point about XLR is that it is an industry standard package for delivering power over line with signal included. Or that 5 pin din was used to power computer keyboards (just with the pins rearranged a bit) aside from it’s use in midi powered gear - 5 pin din would be the issue then, not midi din specifically. Midi is most similar in voltage and practice to USB power which is used very commonly in this era, in fact it is far less likely to encounter noise than USB powered products but USB is just as likely - actually more likely to fail in my experience as I’ve never had bad 5 pin din cables but I’ve had USB cables go bad (possibly due to small gauge wires?).

So if it’s a problem with 5 pin din, should all USB powered devices also have dedicated power supplies? I mean maybe the answer is yes, I don’t know. I have no problem with extra power supplies, but it seems less likely to me the 5 pin din powering the thru / merger box will cause an issue than it is the source of the 5 pin power will develop an issue, at which point the power source of the box in question will become irrelevant. I had hoped there was a simpler way to say this but in order to be illustrative I figured I would just express fully what I was thinking.

USB is made to (also) deliver power to attached devices - within the specs of the USB-protocol version.
Midi not.

a proper midi-thru doesn’t create any latency (nothing worth beeing discussed) - unless it’s some sort of software switch/router

What part of USB differs from midi? Signal is sent at a low voltage, but the power delivery is at the same level - 3.3v to 5v maximum. You say it’s made to also deliver power but it’s like saying a pie is made to be eaten but a carrot is not. There is nothing superior about the internal parts of a USB cable, believe me, I’ve cut open and spliced enough of them to know that for a fact.

There was no implication that a midi thru, proper or improper, would create latency. Your hypothesis was that since the power is only there for the optocouplers, then it is no good for anything else, therefore the signal may become compromised and if it is unable to deliver consistent power or sufficient power the signal degradation will potentially cause an issue. The issue, if not complete failure of the signal chain, will be a resulting latency. You say I don’t understand, but I’m only following your logic on this.

So whether or not midi latency is expected out of a functional thru device is not something which is being questioned or expected, my statement was that in a case where something is failing but has not prevented the device from working in full, the result will manifest in either missing /misaligned data delivery or in something more benign such as a latency in the signal.

There is nothing in this world which is guaranteed to work 100% of the time all the time, but there’s nothing to say that a device which is powered by usb is any more reliable than a device which is powered by 5 pin din. I still have keyboards from my computers in the 1990’s which have 5 pin din that passed power from the PC to the keyboard, it’s not just midi, it’s 5 pin din which you’re contesting. There’s no reason for 5 pin din to have any less reliable voltage than the source at which the voltage originates from. Certainly no less reliable than power which is passed over usb - they use the same grounded shield and grounded pin with power and signal passed on other pins, the form factor is simply square vs round.

USB is no more made for power delivery than 5 pin din. This is something you’ve been sold by the industry that is selling you USB as the standard.

I leave you to it. I said what i have to say about it.