Guys, sorry for the ignorance, but I really don't have any knowledge about the situation that follows, and that's why I'm asking for your help:

I have a MIDI controller (Ableton Push 2) that requires a 12V AC 1.25A power supply to function properly. (It does work when plugged into the computer's USB port, but the device's lights are almost completely off without the power supply, and that's exactly the problem I want to avoid with the cable I bought.)

Anyway, I like to create music and camp, and I'm often in places without electrical power. With that in mind, I bought this USB-C input to 12V output cable so instead of powering the device with the 12V power supply, I could do it by plugging the cable directly into my MacBook.

The problem is that everywhere I've looked for information says these cables need to be connected to a power adapter, not directly to the computer.

I'm unsure whether I should plug the cable into the computer, fearing that something bad might happen to both the MacBook and the Midi controller.

Another important detail: The manufacturer of the cable says it delivers 12V with 3A. However, the MIDI controller requires 1.25A. I'm also concerned that this difference might cause some issues.

Thank you very much for your help.

 

Welcome to AAC.

The photo doesn't provide enough information to authoritatively answer your question, can you provide a link to the product?

In the absence of more information my answer can only be surmise, but with a bit of SWAG energy, here's my take on it:

First, I'll restate the problem in case I've got that wrong.

Your Problem:
You have a device that needs 12V@1.25A and you are trying to avoid an additional power supply by using a MacBook Type-C port as a source. (Plugged in directly, the device "works" but weakly—that is, the LEDs do not light fully)

Your solution:
You've purchased a cable with a Type-C connector on one end and a male 5.1mm plug on the other. The cable (in some way yet to be clarified) provides 12V@5A when one or the other end (the crux of the issue) is plugged into an appropriate source.

You are hoping that if you plug the Type-C connector side into the MacBook, 12V@5A will be available from the coaxial connector side.

My psychic reading:
The cable you have purchased must be one of two things:

1. a PD Trigger* whereby electronics hidden under the overloading on the Type-C connector talks to the MacBook and negotiates 12V@5A and so that power appears on the other end, or;
   
   
2. a PD provider (or just a cable!) whereby 12V on the male end will produce 12V on the Type-C end.

The second case seems unlikely for a couple of reasons. First male coaxial plugs are generally used for output not input. Second, the complications of such an arrangement are too many to contemplate and while some odd things are, in fact, manufactured, the probabilities do not favor it.
*a PD Trigger is device that negotiates a specific current and voltage from a PD provider, there are dedicated ICs for this purpose.

PD (Power Delivery) is the standard that uses Type-C connectors to offer power at various fixed voltages, and even continuously variable ones) based on negotiation between source and sink. The capabilities of PD provider sources varies very widely. They will have maximum voltages which may not be sufficient for a sink (power user), maximum currents, and maximum total power (that is, voltage multiplied by amperage which results in a power rating in Watts).

Apple's Type-C ports are actually either Thunderbolt 3 or 4 ports—each is a superset of the Type-C specification and does offer PD output up to 15W. This means, at least in theory, the device you want to power at 12V and 1.2A (14.4W) should be able to be powered by your Mac's PD. But, this depends on negotiation. If plugging it in directly doesn't seem to be working, there is less hope that using a cable with a PD trigger would make any difference.

I can't do it right now, but I can check my 2023 MacBook Pro 16" ports for what they offer. It is surprisingly hard to find out just what they can do (outside the 15W maximum power) on line.

Is is safe?
Maybe. Well, "yes", but since this is based on a mythical ability (psychic reading) I can't take responsibility for saying so without hedging. On the other hand, look at it this way:

If the cable is equipped with a PD Trigger, but your Mac rejects its flirtations, nothing will happen except that it won't work. On the other hand, in the unlikely case the cable expects to provide power from the Type-C end, and receive it with the barrel connector then nothing is going to happen since your device doesn't supply power from it's power input connection.

So, it seems, this either works or doesn't—but there is no obvious way this could do any damage to the MB, for the two reasons above, and for the additional reason that the MB will protect itself against weirdness and will expect voltages well in excess of 12V for legitimate purposes. The MB can be charged via its Type-C port at (depending on model) up to 100W so even if that cable somehow pushed 5A or 12V into the port, the 60W won't do anything except—charge the laptop.

 

The cable almost certainly has a PD trigger inside of it.

If the MacBook is a USB-C PD source, it may provide 12 volts. I say may because 12 volt operation has been deprecated from the USB-C PD standard. Many chargers still include 12 volts but some do not.

If 12 volts isn't available, the trigger may supply the next lower standard voltage, which is 9 volts; whether the PD trigger supports this depends on how it's configured.

At any rate, it either works at 9 or 12 volts if the MacBook supports USB-C PD charging, or the cable will supply 5 volts. No harm will come to the MacBook if it does not.

You might check the documentation for your model of MacBook to see if it supports USB-C PD and the voltages it can supply if so.

 

The cable almost certainly has a PD trigger inside of it.

If the MacBook is a USB-C PD source, it may provide 12 volts. I say may because 12 volt operation has been deprecated from the USB-C PD standard. Many chargers still include 12 volts but some do not.

If 12 volts isn't available, the trigger may supply the next lower standard voltage, which is 9 volts; whether the PD trigger supports this depends on how it's configured.

I think it is a trigger as well, and the idea it is falling back to 9V is consistent with the symptom of weak indicators. I just don't know if the MBP's ports do 12V, as you point out, but they can do at least 15W, so in theory, a boost converter might just...

 

Welcome to AAC.

The photo doesn't provide enough information to authoritatively answer your question, can you provide a link to the product?

In the absence of more information my answer can only be surmise, but with a bit of SWAG energy, here's my take on it:

First, I'll restate the problem in case I've got that wrong.

Your Problem:
You have a device that needs 12V@1.25A and you are trying to avoid an additional power supply by using a MacBook Type-C port as a source. (Plugged in directly, the device "works" but weakly—that is, the LEDs do not light fully)

Your solution:
You've purchased a cable with a Type-C connector on one end and a male 5.1mm plug on the other. The cable (in some way yet to be clarified) provides 12V@5A when one or the other end (the crux of the issue) is plugged into an appropriate source.

You are hoping that if you plug the Type-C connector side into the MacBook, 12V@5A will be available from the coaxial connector side.

My psychic reading:
The cable you have purchased must be one of two things:

1. a PD Trigger* whereby electronics hidden under the overloading on the Type-C connector talks to the MacBook and negotiates 12V@5A and so that power appears on the other end, or;
   
   
2. a PD provider (or just a cable!) whereby 12V on the male end will produce 12V on the Type-C end.

The second case seems unlikely for a couple of reasons. First male coaxial plugs are generally used for output not input. Second, the complications of such an arrangement are too many to contemplate and while some odd things are, in fact, manufactured, the probabilities do not favor it.
*a PD Trigger is device that negotiates a specific current and voltage from a PD provider, there are dedicated ICs for this purpose.

PD (Power Delivery) is the standard that uses Type-C connectors to offer power at various fixed voltages, and even continuously variable ones) based on negotiation between source and sink. The capabilities of PD provider sources varies very widely. They will have maximum voltages which may not be sufficient for a sink (power user), maximum currents, and maximum total power (that is, voltage multiplied by amperage which results in a power rating in Watts).

Apple's Type-C ports are actually either Thunderbolt 3 or 4 ports—each is a superset of the Type-C specification and does offer PD output up to 15W. This means, at least in theory, the device you want to power at 12V and 1.2A (14.4W) should be able to be powered by your Mac's PD. But, this depends on negotiation. If plugging it in directly doesn't seem to be working, there is less hope that using a cable with a PD trigger would make any difference.

I can't do it right now, but I can check my 2023 MacBook Pro 16" ports for what they offer. It is surprisingly hard to find out just what they can do (outside the 15W maximum power) on line.

Is is safe?
Maybe. Well, "yes", but since this is based on a mythical ability (psychic reading) I can't take responsibility for saying so without hedging. On the other hand, look at it this way:

If the cable is equipped with a PD Trigger, but your Mac rejects its flirtations, nothing will happen except that it won't work. On the other hand, in the unlikely case the cable expects to provide power from the Type-C end, and receive it with the barrel connector then nothing is going to happen since your device doesn't supply power from it's power input connection.

So, it seems, this either works or doesn't—but there is no obvious way this could do any damage to the MB, for the two reasons above, and for the additional reason that the MB will protect itself against weirdness and will expect voltages well in excess of 12V for legitimate purposes. The MB can be charged via its Type-C port at (depending on model) up to 100W so even if that cable somehow pushed 5A or 12V into the port, the 60W won't do anything except—charge the laptop.

Hello, and thank you very much for the detailed response!

I am sending you the link from the manufacturer where I bought the cable.

https://www.aliexpress.com/item/100..._main.105.96a6caa4RBx2fW&gatewayAdapt=glo2bra

And the MacBook I will use to connect it is an M3 Pro, just like yours.

I hope that with this information we can have more certainty about the case.