Logic Won't Release CPU on Aux's Issue - Logic Pro X


New Member
Made a video of the issue - I forgot to show my OS and software versions - I will list at the bottom of this post.

When audio passes through a plugin on a bus - the plugin begins to use CPU - when audio stops feeding the bus the CPU usage should drop after a few moments. _ It does not. And to compound the issue Logic does not even release the cpu until a section of the song is played without audio.
I hope there is a button or setting for this - but there doesn't seem to be.

If this users error... smack me around and let me know.... I really can't solve this one.

In text form -
In my tests - the Dynamic plugin allocation - is broken in Logic - Once a plugin uses the CPU in an Aux track the program never releases it as it does with audio tracks.
I did not test with Instrument tracks. So I don't know what goes on with virtual Instruments.
I have spent a total of two days with Logic, so it very well could be user error -
but that seems unlikely - since the dynamic plugin allocation works absolutely perfectly on audio tracks.

My test was easily reproducible. So if someone could verify it is not a "just me" issue that would be ultra kind and much appreciated.

  • Set up 25 audio tracks with any audio clip on them
  • Set up 25 or more Aux tracks.
  • Set the input on all the Aux's to the same bus. Unorthodox I know - but this is only a test - If you want to later set up individual feeds per Aux.
  • Place a CPU intensive plugin across all the Aux's - So you can watch the "Performance meter" - The more plugins the better - up to about 25-90% max cpu usage make for an easy visual.
  • Audio tracks should have a send to feed the aux's input(s)
  • Play the audio watch the CPU usage and hit stop.

Now bypass the Aux's plugins and add the exact same plugins to the audio track directly and you will notice the CPU get used when audio is playing through the plugin - and when there is a gap or no audio the CPU usage drops off.

Logic seems to be treating the Aux's as audio tracks with the input monitor button selected. As if once it detects audio it does not know if more audio is on the way so it just keeps all plugins on and ready.

My specs I didn't mention in the video.
Logic Pro X 10.5.1
OS 10.14.6
2017 iMac 4.2Ghz i7
40Gb Ram