Signal Flow through the Processor List:

The “processor list” is the black box at the top of every Mixbus channel strip. You can imagine the “processor list” as a container for a series of guitar-pedal processors; each processor must be connected to the processor before and after it.

Often, the signal flow is very simple. For example, a mono track will most likely have a series of mono effects applied. In this case, you’ll see a picture like this:

In this example, the signal is processed by the channelstrip EQ, the Compressor, the Fader, and finally a Gate plugin. The signal flow proceeds from top to bottom, and the green “pips” between each plugin show the audio signal connections between each redirect.

But what happens if you want to use a plugin that has stereo I/O? Just like a guitar pedal, you might choose to use only the left-side signal for the mono track. But there are other possibilities as well. The plugin might have 1 input, and create a stereo output (such as an auto-panner, or reverb/delay effect). Or the plugin might have an extra “sidechain” input to trigger a gating or compression effect. Or the plugin might be an instrument that has 16 individual outputs for different drum sounds.

Starting with Mixbus version 3.3, the signal path between redirects is highly flexible, while also using sensible defaults.

Why is this so complicated?

Mixbus tries to do the “right thing” by default. Mono channels will get mono plugins, and stereo channels will get stereo plugins. Virtual instruments will appear with stereo outputs, by default. But if you want to change these settings, there are quite a lot of variables that must be considered.

There are several challenges inherent to the signal flow through a channel using plugins:

  • Plugins may be drag/dropped into any order
  • Some plugins can be fed a “sidechain“signal which should allow the possibility of being sourced from any other track.
  • Often you need to use a plugin in ways that it wasn’t intended (only using one side, for example)

Additionally, each of the Mixbus-supported different plugin formats provide different rules:
1) LV2 and LADSPA plugins typically have fixed I/O such as 1->1, ( 1 input, 1 output ) or 2->2
2) VST plugins typically have a fixed I/O configuration, but can be told that some signals aren’t connected.
3) AudioUnit plugins (Mac) allow the HOST to define how many connections they will have. So Mixbus can request a mono (1->1) or stereo plugin as-needed. But the user also has the option to change the configuration, if they want to do something unusual.

Finally Mixbus can “replicate” plugins. If you try to insert a mono plugin on a stereo strip, Mixbus will automatically create 2 plugins, and send the controls from the first plugin to the second. This allows you to process both sides of the stereo signal using the same settings of an EQ, for example. You can add or remove replicated plugin instances using “Pin Management” ( see below )

Pin Connections

Right-click on a plugin to reveal the “Pin Configuration” dialog:

By clicking on the pin connections, you may drag a connection between the channelstrip signal flow, and the embedded plugin processor. Right-click on a pin to remove all connections to that pin.

One can also bypass plugin instances with a ‘thru’ connection by dragging an input pin directly to an output pin. This connection is latency compensated to match the delay through the plugin.

The “Pin Configuration” dialog provides these additional features:

  • Manual Config : click to enable the configuration buttons, below:
    • Instances : increase/decrease the number of plugin instances inside the processor
    • Audio Out : increase/decrease the number of audio outputs that the plugin can access
    • MIDI Out : increase/decrease the number of MIDI outputs that the plugin can access
  • Output presets ( virtual instruments only ) : click to choose how many outputs the instrument will provide
  • Side Chain : click to enable a sidechain input for the plugin.
    • When Side Chain is enabled, the sidechain source may be managed with the buttons below it.


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