How do I connect MIDI keyboard to C12 (Mac) w/Thunderbolt audio interface?

Hi – after running stone age equipment for a longtime (last version of Cubase was 7), I completely upgraded to a new MacPro with the silicon M2 chip and Cubase 12.

I’m trying to get everything working and catching up to 2023! HELP!

I bought a Presonus Quantum audio interface which works primarily with its Thunderbolt ports, although the unit does have a MIDI In and MIDI Out. The Quantum’s driver has been successfully installed and the unit and my MacPro are reading each other.

I have a Studiologic SL-880 MIDI controller keyboard which has two MIDI outs.

Here are my questions:

  1. Do I connect my MIDI keyboard using either A) a MIDI cable to the Quantum’s MIDI In or B) a MIO Y cable (which has MIDI In and MIDI Out cords both leading into a Thunderbolt cord) and plug that right into my MacPro’s Thunderbolt inputs?

  2. Whichever is the best way, do I need to go into my Mac’s MIDI Setup Utility or not?

Right now, I have hooked my MIDI keyboard up via the Y cable/Thunderbolt ports. Mac’s MIDI Utility is reading all of them, but I don’t even know if I am supposed to use it with Thunderbolt at all anyway. Needless to say, I am NOT getting any kind of MIDI signal from my keyboard via the Y-cable/Thunderbolt.

In Cubase 12, in Studio Setup, I do see Quantum is listed as the audio system with everything active.

In MIDI Port Setup, Quantum is listed as “active” both In and Out and for some reason, so is my MIO Y-cable!

Still, no MIDI signals are happening.



I would go for 5DIN MIDI to the Audio Device in this case. Make sure you connect the IN to OUT and vice versa.

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Dear Martin:

You’re suggesting to connect from the MIDI Out of the MIDI keyboard to the MIDI IN of the Quantum audio interface and then a cable from the MIDI Out of the audio interface to the hardware music modules I own? Somewhere else? My MIDI keyboard only has MIDI Out ports.

How does that send MIDI data to my Mac?


Then it’s just the midi out of the keyboard to midi in. Out means it is sending midi so that’s how it gets there. The quantum midi ports should show up in Cubase.

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This is done in Cubase. Set the Input of the MIDI track to All MIDI Inputs. And the Output to the Quantum MIDI Out.

Martin and Mark:

Thank you for your guidance.

If I am setting this up as you say: via the audio interface’s MIDI In port (from my MIDI keyboard) and then the audio interface’s MIDI Out to my rack-mounted instrument modules, do I need to set this up in Apple’s MIDI Utility as well?



No, you don’t.

OK. I think we finally got this going. Especially with the VST instruments. Thank you so much for helping me with this setup. It has been MANY years between MacPro’s and version of Cubase.

FOLLOW-UP to this topic:

Now that I have everything set up with my Quantum interface, I am experiencing unexpected bursts of MIDI notes after I play anywhere from a few minutes to several. The MIDI notes just keep coming, actually, and I do not know what triggers them.

I unplug the MIDI OUT from my MIDI keyboard, but that doesn’t stop it.

I press “Reset” under MIDI and that does nothing either.

I have to literally shut down Cubase for it to stop.

Just to see if this is happening in another DAW, I set up Garage Band to use Quantum as the input/output and no problems. Obviously, they use AU plug-ins.

I am wondering if there is a setup adjustment I am overlooking that I need to make in Cubase to stop these bursts from happening?

It happens whether I am playing Kontakt, Halion, or other VST instruments. I am genuinely mystified.

Thank you in advance – Drew


To me, it sounds like a MIDI loopback issue. Do you use any virtual MIDI cable software? Do you use MIDI In and Out, or also MIDI Thru with your hardware?

Hi Martin. Sorry for the delay – I was out of the country for one week.

I do not use any virtual MIDI in my set up. I have exactly one MIDI cable that goes from the MIDI Out of my MIDI keyboard to the MIDI In of my Quantum audio interface. As of now, I am only using VST instruments.

I am wondering if this is a buffer issue?


I have shot a 23-second video of the sudden MIDI bursts taking place. It does not take long. You’ll see the bars go highly active and the keyboard on Halion reflecting those random bursts of notes.

As noted, as a test, I opened Garage Band and no issues at all. Even when I opened non-Apple instrument (yes, I know these are AU files, not VSTs).

Maybe the video can help detect what the problem is?

FYI – The buffer size is current 512. As I mentioned, this is a one MIDI cable connection. I used Thunderbolt cables to connect the Quantum audio interface to my MacPro.

Thank you.


I’m sorry, but to me, it looks more and more like any kind of MIDI loopback.

What MIDI Input do you use? Do you use All MIDI Inspus? If this is the case, could you try to switch the inputs of the track and test, which MIDI Input produces this, please?

Do you use any MIDI Remote Device?

I am sure you are right about a loop.

I have a Mackie Control, but it is not connected to the system at all.

On a MIDI track, I have three choices for input – All MIDI Inputs, Chord Pads, and Quantum (which is the audio interface).

I have now discovered two things, as per your suggestion:

  1. Whether I set the input to either All MIDI Inputs or Quantum, MIDI is received only on Channel 1.

  2. When these sudden MIDI bursts appear, it is only on MIDI channel 1.

ALSO: for whatever it is worth, I went into Apple’s Audio MIDI Setup and noticed there are three devices: IAC Driver, Quantum (Presonus audio interface that has MIDI In and Out ports) and something called UCNET MIDI that has no ports. None of these devices are attached in any way.

Thanks – Drew


These ports might be the source of your issue. Remove them, please.

Hi Martin:

Unfortunately, Audio MIDI Setup will not let me remove any of these three devices. They must be an integral part of Presonus’ Quantum drivers. Perhaps there is something in their Universal Control software that needs adjustment – I will launch it and find out

One additional thing I noticed: when I opened Garage Band, and launched an instance of the AU version of Halion SE, the MIDI bursts appeared, as if I was playing them in Cubase.

Just so you know, I am trying to get Presonus’ customer service to help with this too. Somehow I think this problem is related to Presonus. Have issues like this been reported with Presonus units?

I can not get this to work, I am going to have to return this Presonus interface and buy one that I know is compatible with Cubase. I may need a recommendation!

Thanks — Drew

Seems we have reached a dead end with these problems.

Perhaps there is a way to test for a MIDI Loop? I understand one exists.




Have you tried to use MIDI Monitor and observe incoming data on the specific MIDI Ports? Maybe even 3rd party external MIDI Monitor to observe output ports?