Auxilliary sends are simple processors in a bus or track channel strip. They tap the signal at a specific point in the signal flow (pre-fader, post-fader, before or after EQs and other plugins, etc.) and send a copy of that signal to a bus, without affecting the normal signal flow downwards to the channel fader.
Aux sends from several tracks are collectively sent to a bus in Ardour, to create a monitor mix for a musician, or to feed an effect unit. A bus used in this way is considered an auxilliary bus or Aux bus even though it is the same as any other bus. The output of such a bus might be routed to separate hardware outputs (in the case of headphone or monitor wedge mixes), or returned to the main mix (in the case of an effect).
Aux sends are not JACK ports, External Sends should be used to send audio to Jack ports. External Sends can send the tapped signal somewhere else directly, which is not usually possible on hardware mixers.
Adding a new aux bus
New busses can be created using the Session > Add Track, Bus or VCA… menu, and selecting Audio Busses in the Template/Type selector on the left of the Add Track/Bus/VCA dialog.
Adding a send to an aux bus
Context-clicking on the processor box for the track to send to the bus, and choosing New Aux Send … shows a submenu, listing the busses. Choosing one bus will add a send (which will be visible in the processor box). Note that if the only existing bus is the Master Bus, the menu will be grayed out.
Pre-fader and Post-fader Aux Sends
Depending on whether the context-click happened above or below the fader in the processor box, the new aux send can be placed before or after the fader in the channel strip.
- Post-fader aux sends are typically used when using an aux for shared signal processing (FX), so that the amount of effect is always proportional to the main mix fader.
- Pre-fader sends ensure that the level sent to the bus is controlled only by the send, not the main fader—this is typical when constructing headphone and monitor wedge mixes.
The color of the processor will reflect this pre/post position (red for Pre, green for Post). Dragging and dropping the send inside the processor box before or after the Fader processor changes the type of fader accordingly.
Adding a new aux bus and sending a Track Group to it
All members of a group can be sent to a new aux bus at once with a single click. After creating the track group (and adding tracks to it), context-clicking on the group tab allows to choose either Add New Aux Bus (pre-fader) or Add New Aux Bus (post-fader). A new aux bus will be created, and a new aux send added to every member of the track group that connects to this aux bus.
Altering Send Levels
The amount of the signal received by a send that it delivers to the bus it connects to can be altered in two ways:
Using the Send Fader
Every send processor has a small horizontal fader that can be adjusted in the usual way. It is not very big and so this can be a little unsatisfactory if you a very fine control over the send level is required.
Map Aux Sends To Main Faders
In Mixer mode, pressing the button marked Aux on a aux bus will alter the channel strip for every track or bus that feeds the aux bus. Many aspects of the strip will become insensitive and/or change their visual appearance. More importantly, the main fader of the affected channel strips will now control the send level and not the track gain. This gives a larger, more configurable control to alter the level. Clicking the Aux button of the aux bus again reverts the channel strips to their normal use.
Clicking on the small LED in the send display in the processor box of the channel strip will enable/disable the send. When disabled, only silence will be delivered to the aux bus by this track. When enabled, the signal arriving at the send will be delivered to the aux bus.
Send panners can be configured to either be independent of the main panner, or to follow it. The latter could be useful for Reverb effects, or for in-ear monitor mixes delivered in stereo.