Posts Tagged ‘ Sends ’

Effects on a send

Sends are an interesting component of mixer topologies. They allow a combination of mixing and parallel processing. When several channels have non-zero gain applied to a send, they are mixed together, sent through whatever processing is assigned to the send, and then returned on a new channel. The processing on the send ‘hears’ a mix of all the channels being sent to it. As the output of the processing is returned on a separate channel, it does not affect the original source channels. It also means this return channel can be managed separately to the other channels in the mixer.

The most common uses for sends is to add ambience to a mix using delay and reverb. This works particularly well for two reasons:

  1. The ambience is added ‘behind’ the sound, so that the original sound doesn’t need to be altered. This takes advantage of the parallel processing aspect of using sends.
  2. Reverb and delay are usually gain-linear, meaning they do not change their sound with different input levels.  Sending a quiet signal to a reverb will produce the same reverb sound as sending a loud signal to it (the only difference being the output level). Additionally, sending two different sounds to a reverb simultaneously has the same result as sending each sound on its own. This takes advantage of the mixing aspect of using sends.

Of course, reverb and delay aren’t the only types of processing that can be used with sends. Modulation effects such as choruses, flangers or phasers are also common. They work because they also take advantage of the characteristics of sends – they work by adding a sound to the original sound, and they are gain-linear – they work the same way regardless of what the input level is.

Increasingly, it is becoming more common to hear of people using non-traditional types of processing with sends. Interesting things happen when using processing like compression and saturation on a send, because these processes are fundamentally different to additive, gain-linear processes like reverbs, delays or modulation.

The first thing that happens when using compression or saturation on a send is that the processed audio is mixed in with the unprocessed audio. In the case of compression, this will get you parallel compression – which usually requires two duplicate tracks or a specially-designed compressor with a wet/dry control. In the case of saturation, this adds some saturated sound to the original without significatly damaging the integrity of the audio.

The other thing that happens is that you have an opportunity to use the send as a kind of parallel bus. That is, you can send audio from several channels to a single compressor or saturator (which is then brought back into the mix in parallel with the original sounds). It’s important to remember that it is a bus. For example, you might set up a compressor on a send, and send some kick and bass to it. Unlike a gain-linear process such as reverb, the compressor will respond differently to the kick and bass playing together than it would to the kick or the bass separately. The other thing to watch is that the compressor will respond differently depending on how much of the audio is sent to the compressor. Typically, the audio will be more compressed if more of it is sent to the compressor. Similarly, the audio will be more compressed when there are more active audio channels being sent to the compressor because the overall level sent to the compressor is higher. This can make mixing rather complex.


Pre-fader versus post-fader

Without going too deep into mixer topologies, the channel fader sets the gain (you might also think of it as the level or volume, though it’s not quite the same thing) of the sound going into the mix bus (also called the 2-bus or the master channel). Placing effects before the fader (pre-fader) mean that those effects will “hear” the same level, no matter what the fader is set to. Placing effects after the fader (post-fader) will mean that thsoe effects will “hear” a level depending on what the fader is set to. This is particularly noticeable with effects such as compression, which respond differently depending on the level of the sound. If you set up yoru compressor pre-fader, then it will behave the same no matter what the fader is set to. On the other hand, if you set up your comrpessor post-fader, then higher fader gain will result in more compression and lower fader gain will result in less comprssion. In effect, you will use the fader to simultaneously set the audible volume of the sound in the mix AND “drive” the compression. Normally this is not such a good idea beacuse it makes it more difficult to fine-tune the mix (changing the volume changes the compression too).

Post-fader effects are typically not used often, except for sends (also called “aux sends” or “FX sends”). The “send” effectively duplicates the sound and sends one copy to the send channel (the other copy is sent through the original channel as normal). If a wet reverb is applied to the send channel, you’ll have two channels making sound – the original “dry” (no reverb) channel, and the “wet” (reverb) send channel. If the send is post-fader, then the sound level that is sent to the reverb depends on the fader setting. This way, if you adjust the fader (to fine tune the mix, or perhaps automate a fade in or out) the RELATIVE level of the reverb stays the same. On the other hand, if the send it pre-fader, the absolute level of the reverb stays the same (so if you turn the fader all the way down, you’ll still hear some reverb, and if you turn the fader all the way up, you’ll hear less reverb relative to the original sound).