Does CUBASE have a limit on the number of I/O it can handle for aggregate devices?


I have two different aggregate device setups.

The smaller one consists of a MOTU 828MKIII Hybrid and a MOTU 16A. This pairing produces an aggregate device with 64 ins and 62 outs. The MOTU 828 is the clock source, everything is set to 48khz. This device operates without issue in Cubase at a buffer of 256, 32bit float processing, ASIO set to normal, boosted audio priority, and a disk preload of 2 seconds. It also works without issue in my other DAWs (Logic, Studio One, Bitwig, etc.)

The larger aggregate device adds one more interface to the above and consists of the MOTU 828MKIII, the MOTU 16A, and the Expert Sleeper ES8. This creates a device with 76 ins and 78 outs. As before, the MOTU 828 is the clock source, everything is set to 48khz. This device runs fine in my other DAWs, but Cubase will not work with it. If I try to use this device with Cubase, the CPU meter overload indicator is constantly on and cannot be clicked to reset. However, none of the activity meters show any activity.

picture 1

The program GUI is responsive, but no soft synths or wav files will play; there simply is no audio produced by the system when I use the larger aggregate device and and that indicator is active.

However, if I go into Audio Midi Set Up (with Cubase still running) and remove the ES-8 from the aggregate device (making it 64in/62out again), the CPU overload indicator immediately turns off and everything plays normally.

picture 2

This leads me to believe that there is an I/O limit on aggregate devices.

Is there?

Thanks for reading this far!


EDIT: SYSTEM SPECS: iMac Pro 10 core, 64gb, macOS Big Sur 11.6.5, CB Pro 12.0

The I/O limit for Cubase itself is 256 inputs and 256 outputs.

Maybe different ASIO-Guard settings can help?

Thank you for replying!

I should have mentioned that changing the settings for ASIO Guard seems to make no difference. IIRC: I make the change, apply it, the CPU indicator is free/blank for 1 or 2 seconds, then it comes back on and stays on.

Thanks again.

Hi !

Did you find a workaround ?
I have the same issue on Monterey 12.3 .

Hey there.

Nothing yet. I sent in a support request on this and so far radio silence.

I’ve been working with the “smaller” device as well as I can given the ASIO guard issues discussed elsewhere. But that means not using any of my eurorack and tape-based gear (with Cubase at least) which is a bummer.

Thanks for the question.

Hi ! Thanks for the reply .
I have this issue using 2 RME ( UFX & UC ) .
It seems weird because it works for you with 2 MOTU .
By the way I had an ES 8 like you .
I have now an ES 3 & 6 connecting to the UC ADAT .

I really think it’s a limitation on the number of channels from an aggregate device…the smaller configuration is 64in/62out. The larger is 76in/78out. Maybe it’s going over the number 64 for IO that causes the issue.

I think I will create another device that is only 66in and see if there is a problem. I’ll post my findings later.

About the ES8: I have two older MOTU 828MK2s connected via ADAT to give me 8 in/8out on the ES-8’s ADAT ports. Works like a charm! (In other DAWs…)

Also experiencing this issue in Cubase Pro 12.40 on Monterey 12.5. Going to file a ticket. Bitwig handles the aggregate device with 4 devices just fine.