Baffled by a USB data lead problem

[Magnum Valentino]

Trying to make this simple because I'm prone to complicating matters:

I've bought a MIDI keyboard, a wee M-Audio one. It's powered and connected by USB Mini.

The bundled lead (which is too short) enables me to use it as a MIDI controller in Garageband on my late 2014 Mac Mini running Big Sur 11.1 AND on my mid-2012 Macbook Pro running Catalina 10.15.7.

It works perfectly on both. Stable connection and instant response. No issues.

However, the longer lead that I bought (which I made sure listed 'data' in addition to charging) will connect to the newer Mac Mini for full functionality but only for charging (as indicated by the lights coming on) on the Macbook. It doesn't appear in the list of MIDI devices after scanning and won't trigger sounds, but, annoyingly, the computer DOES register that there's an active input of some kind.

So, in summary, one lead works perfectly on two machines, and another lead only works on one machine. But leads don't have software or anything in them that I could reason "oh, that's why it's not working", and there's no easily identifiable variable to target and fix.

Any ideas what's happening?

[touchingcloth]

How long is the new lead? Do you know if there's a difference between the USB ports on the Macs? If it's a particularly long cable and the working Mac is using USB 3 and the non-working one USB 2, then that might explain things.

Do you have any other devices with a female USB mini port which support a data connection? That would help work out whether it's data connections over that lead in general which are affected or something peculiar to the keyboard.

[Sonny_Jim]

USB really isn't made for long distance data transfers, especially the little diddly mini cables, that's why most devices that have leads longer than ~1M ends up using a Type-B plug.

Try putting a powered hub in between the Mac and the keyboard.  Also how long is the cable?

[Magnum Valentino]

How long is the new lead? Do you know if there's a difference between the USB ports on the Macs? If it's a particularly long cable and the working Mac is using USB 3 and the non-working one USB 2, then that might explain things.

Do you have any other devices with a female USB mini port which support a data connection? That would help work out whether it's data connections over that lead in general which are affected or something peculiar to the keyboard.

Bet you that's it. It's 5 meters. I've an even longer one for the e-drums, but it's the different port like mentioned below (the one commonly called the 'printer' connection). I'm not sure I do have any other devices with a female Mini though, it's so uncommon. I'll have a hoke, but I'd say the USB2/USB3 difference could be the issue.

USB really isn't made for long distance data transfers, especially the little diddly mini cables, that's why most devices that have leads longer than ~1M ends up using a Type-B plug.

Try putting a powered hub in between the Mac and the keyboard.  Also how long is the cable?

Another good suggestion, think I have a powered hub going spare somewhere. Thanks both!

[Magnum Valentino]

Seems to be USB 3.0 on both machines, so that shouldn't be the problem. Gonna try and get my hands on a powered hub to see what difference it makes.

[Magnum Valentino]

Solution seems to be running it through a powered hub, as suggested.

I'm annoyed that I don't understand it, but grateful that it works. Thanks to you both for your time :-)

[Sonny_Jim]

I'm annoyed that I don't understand it,

USB is a high speed data thing, high speed stuff definitely does not like noise.  Short distance it's fine, but what you'll find is that thin cable over long distances = shitty data transfer capabilities.  That's why those chunky USB printer cables normally have a braided shield, to keep the noise out over a long run of cable.  The cheap ass mini USB stuff barely has enough copper for charging, let alone shielding and that.

The hub helps as the USB port on the computer may not be supplying enough juice, or it might be that the hub has some better filtering on it.  You can get cheap little USB monitors for about 2 quid from China if you want to investigate more.  They are handy to have when diagnosing weird issues.  If you put the monitor on it and see that it's dropping below 4.7ish volts then you know something fucky is about to happen.

[touchingcloth]

Yes the power attenuation was what I was getting at with the USB 3 versus 2 suggestion really, and how a more powerful port will be more reliable for particularly long cables. It probably stands to reason, ish, that Apple would do something to reduce the voltage on a Macbook versus a Mac Mini on the assumption that it will be running on battery power.

Looking online it seems there are ways to hack your Macbook to increase the default power delivered over the USB ports, but that's probably not a great idea. If having a powered hub is annoying due to it requiring an extra AC socket, then if your Macbook has enough appropriately positioned USB ports then you could look at using a Y-cable instead so that the extra current is being provided by multiple ports from the laptop rather than from the mains.