Today we are going to have a more in-depth look at the Send and Sub Group parts of the mixer and how they work.
Send Buses:
The Send dials on each channel, on a mixer, are used to send audio to three different types of external equipment. The three types of external equipment include Effect Units, Monitors, and Sub-Woofers. The Send Bus may also be referred to as an aux (Post-Fader) or Fx (Pre-Fader) Bus.
Each channel has a set of send dials which pass audio from the channel to one of the Send Buses. On some mixers send dials can be switched into Pre-Fader or Post-Fader mode and on others they are locked in either Pre or Post Fader mode or have combinations of both.
"Pre" and "Post" Fader refer to where the audio travels before it is sent to the Send Bus. Pre-Fader means that the audio being sent to the Send Bus does not travel through the channels' fader before being sent to a Send Bus. This effectively means that if you change the position of the fader it does not change the amount of sound being sent to the Send Bus. Post-Fader means that both the channels fader and send dial will affect how much audio is being sent to the Send Bus.
The overall output volume of each Send Bus is also then controlled by a separate fader or dial. Note that the channel dials labelled "send 1" will send audio to number one Send Bus from that channel, the "send 2" will send audio to number two Send Bus from that channel and so on and so forth.
Now most of the time Pre-Fader mode is used to when attaching the output of the sub buss to monitors. Post-Fader mode is normally used for attaching the output from a Send Bus to an Effect Unit.
Sub Groups:
Sub Groups are used when you have sent several channels and want to increase or decrease them volume wise without changing the mix. For example: when you have mic'd up a drum kit and have a good mix with your drums and then you add guitars to the mix you find that the drums are too overpowering. Instead of shifting the five channel faders that the drum kit is assigned to, you can assign those faders to a Sub Group and control the overall volume of the drum mix with one fader.
Note that in my "analogue mixers: 101" article I described the Sub Groups working much the same as how the Sends do. This is however incorrect and you don't assign a channel to a Sub Group by a dial but by a set of little buttons beside or above the channel fader. Not every mixer has Sub Groups.
The channel fader then controls how much audio is sent to the Sub Bus. The Sub Bus is then sent either directly to the master out sockets on the back of the mixer or through the Master Fader then to the master out sockets depending on the internal wiring of the mixer.
Appendix:
Monitors – Also called Foldbacks are speakers set on stage for musicians, singers or speakers to hear themselves. In some venues monitor speakers also known as monitor wedges are not used and are instead replaced with IEMs (In Ear Monitors) which are not going to be covered in this series.
Bus - a route audio can travel.
Zach Radloff lives on the Gold Coast and is studying IT and Multimedia at university and is also a qualified Live Production, Theatre and Events Technical Operations Technician.
Zach Radloff's previous articles may be viewed at www.pressserviceinternational.org/zach-radloff.html