Alesis IO Dock: Power through MIDI cable

[FEF]

I'm seriously thinking about getting the Rolls MidiBuddy. It's made such that it can get power from the MIDI cable. The manual says pin 3 is 9v-15v, and pin 1 is the ground.

The IO Dock has an input of 6v. That's a problem because even if I put power from the jack to pins 3 and 1, I'm still 3 volts short. I suspect that one of the reasons it's only 6 volts is because anything more through the USB port would fry what's plugged into it.

Here's where it gets interesting, though. The IO Dock has phantom power. That means its got 12v-48v somewhere, but it may not have the current from the step-up transformer that's providing the the phantom voltage. I split the case of the dock and didn't find any small transformers. This leads me to think that I can't find the voltage I need in the IO Dock.

It looks like I have 2 options: 1) use the extra space in the dock to try and get 9v to the 2 pins of the midi out. 2) make a short MIDI cable that splices in 9v from another wall wart.

Anyone have any other thoughts?

 

[Crater]

So, you're trying to power the MIDI buddy via the MIDI port on the Alesis I/O dock? Sounds like a bad idea to me...unless you're really skilled at working on SMT circuit boards.

A simpler solution would be to make a MIDI power injector in a small stompbox type enclosure. 2 MIDI jacks and a jack for the MIDI buddy's power supply. Similar gizmos are used to supply phantom power to mics when a mixer or other device doesn't supply phantom power natively. It would be fairly simple and cheap to build a power injector, and you won't have to modify your I/O dock. Yes, there's an extra box and cable, but still just the single MIDI cable going to your foot controller.

Also, you should be aware that the standard MIDI spec states that pin 1 is "N.C." or not connected, so it's possible that a MIDI cable won't even have 5 or 6 conductors and that there won't be electrical continuity from pin 1 to the pin 1 of the other connector. Check with an ohm meter, worst case you may have to make your own special MIDI cable.

No doubt the phantom power from the I/O dock is supplied by a charge pump. It uses AC current and a ladder type circuit of diodes and capacitors to multiply the voltage. It's very low current though, so I wouldn't try to tap it to power the MIDI buddy.

 

[FEF]

So, you're trying to power the MIDI buddy via the MIDI port on the Alesis I/O dock? Sounds like a bad idea to me...unless you're really skilled at working on SMT circuit boards.

I have the skill to solder leads to the pins as they come out of the circuit board, assuming they don't have traces that go somewhere non-conventional. For me, that's the easy part, but there's no value in it. I'd need a different power source, or run two power supplies to the IO Dock. It can be done, but other options are easier and less invasive.

A simpler solution would be to make a MIDI power injector in a small stompbox type enclosure. 2 MIDI jacks and a jack for the MIDI buddy's power supply. Similar gizmos are used to supply phantom power to mics when a mixer or other device doesn't supply phantom power natively. It would be fairly simple and cheap to build a power injector, and you won't have to modify your I/O dock. Yes, there's an extra box and cable, but still just the single MIDI cable going to your foot controller.

I hadn't thought of that. Couldn't tell you why, because I've dealt with them quite a lot. It's true that a small project box with 2 5-pin connectors, a connector for power, and a bit of wire, could be made fairly easily. This is why I have to ask the sometimes silly question.

Also, you should be aware that the standard MIDI spec states that pin 1 is "N.C." or not connected, so it's possible that a MIDI cable won't even have 5 or 6 conductors and that there won't be electrical continuity from pin 1 to the pin 1 of the other connector. Check with an ohm meter, worst case you may have to make your own special MIDI cable.

Yes, a MIDI cable could not be used, as I've not seen a 5 conductor cable sold as a MIDI cable. I'd make one.

No doubt the phantom power from the I/O dock is supplied by a charge pump. It uses AC current and a ladder type circuit of diodes and capacitors to multiply the voltage. It's very low current though, so I wouldn't try to tap it to power the MIDI buddy.

Right. Had I seen a small transformer, I might have stood a chance, but it's just not in the math. Thanks for confirming my thinking.

Looks like the breakout project box, or the dongle idea are the ones to run with.

Sometimes I think I'm the only one the world with odd problems like this.