Multi-Unit Apollo Configurations & Pro Tools 64 Channel I/O Limit


  • This article only applies to multi-unit Apollo configurations using Console 2.0 under Mac OS X where the total number of available inputs and outputs (analog, digital, virtual, etc) exceed 32 channels each. Single Apollo configurations will always have less than 32 inputs and 32 outputs.
  • In UAD v9.0 and later, the "Core Audio" panel is labeled as the "I/O Matrix" panel. The Core Audio panel settings in this article apply to the I/O Matrix panel in UAD v9.0 and later as well. 


Pro Tools limits your total number of inputs and outputs to 32 channels each when using third party non-Avid hardware. If you are using an Apollo 16 or multiple Apollo units in a multi-unit configuration, your total potential number of input and output channels will exceed 32.

How can we work around this?

First, head to the Core Audio panel in the Console Settings window (Console > Settings > Core Audio). You will need to manually reassign the channels you want to access in Pro Tools so that they fall within the first 32 channels in both the input and output columns. Typically, Apollo users will sacrifice either Virtual or Digital (S/PDIF, ADAT, or AES/EBU) inputs and outputs to make sure all of the Apollo's analog inputs and outputs can be used in Pro Tools when using multi-unit configurations.

How do we achieve this?

If you are using an original (silver) Apollo or Apollo 16, you can select one of the I/O presets already available that matches your configuration which will limit your input and output channels to 32 automatically. For example, if you’re using two Apollo (silver) units, select the “Multi-Apollo PT Legacy” preset from the I/O Preset menu. If using two Apollo 16 (silver) units, select “Multi-A16 PT Legacy”. Once you have selected the appropriate I/O preset for your system, proceed to resetting the Pro Tools I/O as described below.

If you're using an Apollo 8, Apollo 8p, or Apollo 16 mkII, you will need to manually configure the Apollo's I/O on the Core Audio panel in Console Settings. First, change both the "# Inputs" and "# Outputs" options to "32 (PT Mode)" using the fields at the top right of the Core Audio page.

Setting "# Inputs" and "# Outputs" to "32 (PT Mode)" on the Core Audio page

Now, if any inputs or outputs that you need to use were cut off by limiting the I/O to 32 channels, you will need to manually reassign those inputs or outputs within the first 32 channels. First, click anywhere on the input channel you want to reassign. Select the device, followed by the channel type, followed by the input (see below). Please note that there is no “done” or “apply” button – simply click the “x” to close the window after making your assignment.

Selecting and reassigning an input channel

If there are multiple channels in a row that you want to reassign in sequence, you can use the Cascade switch to save time. Manually reassign the first channel you want to change, click the Cascade switch, then click, hold, and drag down from that channel. Release on the last channel you want to reassign. All of the channels you just dragged over will be reassigned in sequence starting from the first one you clicked on. Click the Cascade switch again to exit this mode. See the Console Settings chapter in the Apollo Software Manual for details on using the Cascade switch.

Using Cascade to reassign input channels in sequence

 Repeat this process for all input and output channels that you want to reassign.


 Selecting and reassigning an output channel

Using Cascade to reassign input channels in sequence

Once complete, you can save this setup as an I/O Preset for easy recall and switching by clicking the "Save" button at the top of the Core Audio page. If you switch between DAWs, you will probably want to have an alternate setup saved that uses all possible inputs and outputs for when you are not using Pro Tools (most DAWs do not limit you to 32 channels of I/O as Pro Tools does). 

The last step is to reset your Pro Tools I/O to reflect any changes you made on the Core Audio page. Follow the directions below to reset your Pro Tools I/O:

  1. You will first need to make sure that the Apollo is selected as your Playback Engine within Pro Tools. To do this, open Pro Tools and navigate to Setup > Playback Engine and make sure 'Universal Audio Apollo' is selected.

  2. Next, navigate to Setup > I/O and click on the 'Input' tab when the I/O Settings window appears.

  3. On the 'Input' tab, select all paths shown and click 'Delete Path'. Delete all paths on this tab so it is completely empty.

  4. Once all paths are deleted, click the 'Default' button. This will re-populate the tab with the correct paths.

  5. Repeat these steps for the 'Output', 'Bus' and 'Insert' tabs as well.


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