Cubase 12 Upgrade ASIO-Guard Issue

I’d like to just give a shout out to Daniel for starting then curating this discussion so artfully, and to everyone who added really helpful observations and suggestions. This thread did not degenerate into a “C12 sucks!” miasma of unhelpful posturing.

FWIW, although my challenges with C12 share some similarities with Daniel, there is an added dimension: I get random, continual CPU spikes that peg the CPU meter even with very few (sometimes only 1 or 2) plugins instantiated. I noticed this first with Kontakt, but it seems to affect almost everything. ONE time I had no CPU spikes even after leaving a small project looping playback overnight. I also successfully played that same project later with all tracks record enabled. I thought I was in the clear, but the very next project I started, the random CPU spikes returned. (Unfortunately all that I remember about the problem free project is that I was using ONLY VST3 versions of plugins, but I don’t remember the specific plugins I used.)

Changing various buffer and ASIO guard settings have had little real effect during all of this.

Thank you!

iMacPro 10core, 64gb ram, Big Sur 11.6.4, Radeon Pro Vega 56 8 GB


Thanks Matthias, we all appreciate yours and Steinberg’s help and hard work.

However, I have one glaring question: How come none of the beta testers noticed this? It seems like a huge issue that is extremely noticeable at first. Not to keep repeating myself but I had the same question when Cubase 10.5 was released and it had the same type of extreme CPU spikes. How would something like that NOT have gotten noticed or addressed before release?


I have only two plugins with a Multi-Processing option in most of my projects:

  1. Superior Drummer 3
    That is already running with no. of cores set to 1 over here, since Toontracks MP is known to be broken when running inside a Host running on MP as well.

  2. U-He Repro and Diva
    Both of them have their best performance with MP “on”. I know that Urs thinks otherwise and recommends turning it off. But Urs is on Mac, he rarely has experience with PC anymore these days. While turning MP off might be useful on a Mac, it really works VERY well in Cubase on Windows.

Having said that, the plug-in that causes the problem over here is Superior Drummer 3. Activating a MIDI-(not instrument) track going to SD3 as a rack instrument makes the CPU Meter going mad and causes a lot of crackling and noises due to CPU overload.

That does not happen with C11. When I load the very same song in C11, activating that said MIDI-track no such thing as in C12 happens. No crazy CPU Meter spiking, no crackles, no noise. It just works.

What is also strange is the significant delay with muting of audio when switching back from that problematic track to any other track. The CPU Meter goes to Zero and then back. It seems like Cubase is unloading plugins and loading them again.
Again that does NOT happen with C11 in the exact same project.

Another thing, though I don’t know if that is of any use for you:
SD3 is one of the few VST2-plugins I still use. In current projects I also have a couple of VSTs (mainly Soundtoys and UAD), but SD3 is the only VST2 VSTi that I use.

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Thank you George for the kind words! I too, am very pleased and encouraged by everyone’s productive participation. I appreciate you all for sharing your insightful contributions! If this discussion helps improve Cubase, even if just a little, we all benefit in the end!

I think we all share the same goal/wish here - we just want Cubase to work the best it can!

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Regarding the Midi to Instruments track - That’s a very interesting addition to the discussion. Thank you Rainer_Hain for sharing the details.

Let’s see what Matthias reports back to us regarding “multi-processing” currently under investigation.

Video evidence of the issues I’m having. I have no idea how to get past this. It’s rather disappointing. I accept it could be down to even a specific plugin but where do you start with that?
C12 vs C11 performance issues.

Yep I must confirm I’ve had the same issue here - very obvious issues with ASIO Guard and in fact out-of-character CPU spikes in general with VSTis engaged in CB12 … have reverted with current projects to using 11 for now until a fix is released.

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@pkmusic Exactely the same behaviour I have over here.

It’s absolutely possible that a specific plugin or a combination are the culprit(s). But I have no idea where to start looking. Superior Drummer 3 could be it, but I don’t have another drumsampler anymore to try and check my routing with the multiple outputs in 6 groups going in two busses. I believe it could have something to do with multi outputs and a complicated routing together with a specific plugin, but e.g. removing all UAD plugins in those cahnnels and groups didn’t help.

I’m lost with this problem right now.

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I too can confirm Asio Guard spikes here in Cubase 12. Never had this problem in Cubase 11.

It feels like Asio Guard might be overworking itself in order to lighten the load on “realtime” and “peak”? Not sure how it works, but it does kind of feel that way.

I’m noticed the same problem while using the avenger synth

It must be a nightmare to attempt to test software and factor in another 50% worth of foreign add-ons. Perhaps in the changes away from VST2 there is a memory allocation issue. It runs so well with the demo songs. Possibly on Macs this is issue is not as bad? Need a poll there . . .

Hi Matthias,

I’ve checked a couple of projects on Cubase 12, none of the effects plugins used in them had any of their own multi-processing. Yet, the Asio Guard spikes still occur.

As far as VST instruments go, like Kontakt, I’ve tried both on and off for multi-processing. No difference. Asio Guard spikes still occur.

Using Windows 10. Thanks.


Hi all.

Just a quick update.

Apple released a point update to Big Sur this morning. It’s now at 11.6.5. I performed the update. The random CPU spikes and related issues are not happening for me anymore. I’ve tried creating simple projects using VSTs like Padshop, Omnisphere, and Kontakt and I have not hit a random spike yet. Projects that were formerly spiking are not. (I do not use VST based multiprocessing if I can avoid it btw.)

I have no idea whether or not the OS update is related to the lack of issues, but I wanted to flag it for the group. Perhaps someone else can give it a try?

I have run across a different problem with Aggregate devices. It is not germane to this topic so I will post about that separately in the forum.

Cheers all.


What is that? Thanks.

Maybe I’m being thick, but what do you mean by a plugin with ‘Multiprocessing’? Can you give some examples?

Hi @SledDriver ,
Multiprocessing means processing on multiple cores in the same time. When running the plugin or VSTi inside a host application - like, e.g. Cubase - the host is taking care for the multi-core audio processing . If a plugin is doing its own multicore processing, it is likely to compete with the sequencer’s processing threads which can lead to bad performance. That’s why Steinberg recommends to let Cubase take care for handling the processing and let the plugins’ multicore processing disabled - in case they offer to disable it (e.g. Kontakt or Halion have that option).

Aha. Thanks for that. Is there an easy way to see which of your plugs have this? It isn’t indicated in the Plugin Manager. I wonder if there is a list anywhere?

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Having the same. Windows 10 (all current updates), Ryzen 3950X, Cubase 12.

My orchestral template worked fine in Cubase 11, but loading it in Cubase 12 causes huge CPU spikes making it unusable. Have gone back to Cubase 11. Disappointing for an ‘upgrade’ that promised to be faster/sleeker/optimised.

I’ve got Hyperhtreading on, but given it works perfectly at 128sample buffers on Cubase 11, I’m not sure that is the issue.

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An Aggregate Device is a virtual device driver for Mac OS…with an Aggregate Devices it is possible to combine different physical inputs and outputs from different interfaces and treat them like one virtual device. The OS ensures the devices are synced and locked to each other. The DAW just sees and treats it like a single device.

It seems like there is a limit to the number of I/O supported in aggregate devices. The full question is here:

Thanks for asking.


I’m on this thread as I’m finding very uneven core loading/allocation on my 5950x.
I’m a big acoustica aqua user an all their plug-ins are multithreaded with no way of turning off.

It will be interesting to see how this gets resolved.


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