IK Multimedia Tape 24 Plugin STRANGE ISSUES on busses only

I’m have a strange issue that I’m hoping someone can shed some light on. Using the IKM Tape 24 plugin, I can place an instance on every track in a session, no problem. The issue comes when I attempt to place the plugin on my bus tracks.

Typically I only place this plugin on the busses and I usually have the following busses: Drums Bus, Bass Bus, Guitar Bus, Keys Bus and Vocals Bus. When I place the plugin on theses busses Cubase throws a CPU overload warning and Cubase runs like crap. Playing audio intermittently and starting and stopping a lot.

What I can’t understand is why I can place this plugin on all my tracks (except busses) without issues, but if I place the plugin on my busses and only my busses, it breaks Cubase.

Cubase Pro 12 v12.0.70
Windows 11 Home v22H2
AMD Ryzen 9 5900X 12-Core Processor
AMD Radeon RX 6600
32 GB RAM

Any ideas?

This could be because one of your CPU cores gets saturated and just cannot keep up with the workload, and that depends on how Cubase schedules channels and buses on the different cores, and that can actually depend on your routing setup. Very broadly speaking, the plugins of one channel need to be scheduled on one CPU, and if that channel has many resource-hungry plugins, it can overload your system, even if all other cores are basically sleeping.

How exactly the scheduling works is rather complicated and can be fully answered probably only be the developers. It also can change quite dramatically from version to version, C12 e.g. behaves imho quite differently than C11.

Now that doesn’t fully explain what happens in your project, but I can imagine that you ran into a constellation with your plugin setup and routing where too many CPU hungry plugins get scheduled on one core, and the IK tape, which is really demanding anyway, gives it the rest.

Do you have any other plugins on your buses?

I ran tests without any other plugins on the busses or tracks feeding the busses.

Have you tried a completely empty project?
I did a test here, with 4 channels of audio, each having one instance of Tape Machine 80, going into one group with no plugins. That results in pretty much the same ASIOGuard Usage as 4 tracks of audio with no plugins each going into a group with one instance of Tape 80.
So it has nothing to do with the plugin or whether it is on a bus or audio channel. Somewhere in your project something stacks up in a way that overloads at least one core if you put the plugins on your buses. Maybe something on your Master bus?

Did some more testing. The only processing taking place were instances of Tape 24. I topped out at 26 instances @ 96kHz before running into issues. Which is to be expected. When I have more time tonight I’ll be able to give this the attention it needs to determine the issue.