Working with Processing
Posted by Alex Skinner, Last modified by Alex Skinner on 13 February 2018 02:24 PM
Press a fader strip Sel key to select a channel, press the Processing key to display the available processing for the selected channel. This shows a bank overview of 8 channels, the highlighted channel on screen relates to the selected channel. Select a processing block to view the parameters.
For input channels, there are the following processing blocks available:
For output channels, there are the following processing blocks available:
FX return channels have PEQ available only.
The on-board rotaries control some useful parameters for quick access, all other parameters can be changed by touching the value on the screen and adjusted by using the screen rotary.
The preamp section converts a microphone or line level signal into a digital operating level, ready for processing. In this processing block the routing, gain, delay and polarity can be changed to setup your input signal appropriately for the mix.
48v – Press and hold this to turn on 48v power or ‘phantom power’, which is used for condenser microphones and active DI boxes that require power to work.
Pad – When a signal is above the required level with a low gain setting, press the Pad key to attenuate the gain by 20dB.
Gain – Use either the on-board Gain rotary or select the value on screen and adjust using the screen rotary to change the amount of gain being added to an input source. Usually, aiming for the input level to reach 0dB, or ‘unity gain’ is a good place to start, if the level peaks then reduce the gain accordingly.
Use the on-screen trim control to attenuate the signal to a desired volume. The optimal control area on a fader is at 0dB, so if the channel is too loud with the fader at this position, the ‘trim’ can turn the signal down for maximum control on the fader.
Pol – Selecting this button reverses the polarity. A common use would be when there is a microphone pointing at the top of a snare drum where the sound travels away from the microphone when the drum is hit, with a microphone on the bottom of the drum the sound is travelling towards the microphone. This means that one signal is starting with negative energy and the other with a positive energy. Switching the polarity of one of these microphone inputs will mean the two signals work together instead of cancelling each other out.
Adding delay means adding to the amount of time the signal takes to arrive from the input stage to the output stage. This can be used to time align a kick drum in and kick drum out microphone for example, delaying the kick out microphone to a point where it is in line with the kick in microphone will mean the two channels will arrive at the speakers at the same time.
Odd and even channels can be switched into one stereo channel, this combines the processing for the two channels, uses one fader for volume control, and provides further options for the stereo image settings. There is a width control ranging from Stereo to Mono, and multiple modes available:
The gate stops the signal from passing until it reaches a specified level. To activate the Gate, press the In button on screen, or the In button on the surface.
Threshold – Adjust this to specify at what level the gate opens to let signal through. There is a Threshold rotary on the surface as well as on screen.
Depth – When the gate is closed, the depth adjusts how much the signal is reduced by.
Attack – How fast the gate opens.
Hold – How long the gate stays open for.
Release – How long the gate takes to close.
Side chain - Trigger the threshold from itself, or any input or output channel. Press the filter in to activate, a High Pass Filter, Low Pass Filter or Band Pass Filter mode is provided to get a more accurate trigger from the source.
The insert section facilitates routing the audio out of an output and back in to the input channel, for use with external processors in either hardware or software applications or internal FX units. To active the Insert, press the ‘In’ button placed to the bottom right of the screen. The operating level can be changed to suite different hardware and software levels.
To route to hardware equipment, assign the Send to a physical output on the local I/O or Slink I/O. From that output, it is possible to patch into an external compressor for example, then patch from the output of the compressor to a physical input and assign that input as the return.
To route to software on a computer or network processor (Digigrid), assign the send and return to a virtual port on an I/O card or a USB port. The channel can then be processed via a DAW or plugin software such as Waves sound grid.
HPF and PEQ
Adjusting the EQ helps to shape the sound of the signal to sound either as natural as possible, for effect such as making a channel become more prominent in a mix, and prevent feedback. The HPF In button is placed on the surface to the left of the screen with a rotary to change the frequency, and also on screen to the bottom left of the EQ graph. The PEQ controls are all available on the surface and on screen.
HPF – The ‘high pass filter’ or ‘Low Cut’ is used to filter out low frequencies from sources that don’t have low frequency information naturally, such as a vocal or wind instrument.
PEQ - 4 band equalizer with a gain, frequency and width per band. The HF and LF bands have a shelf option which can be accessed by scrolling the width all the way to the left on the screen only. Play around with the settings to find what is needed for each channel, switch the EQ in and out to hear the affects. For live sound, it is recommended to cut frequencies rather than to boost where possible, as this prevents feedback.
A compressor can be used to reduce the amount signal can increase once it has passed a specified level. To activate the Compressor, press the In button on screen, or the In button on the surface.
Ratio – How many dB’s the channel will increase after the threshold. For example, with a 4:1 ratio: every 4 dB after the threshold with only increase by 1dB. Infinite ratio limits the signal at the threshold.
Threshold – Adjust this to specify at which point the compressor will start taking effect on the signal. A physical rotary is available for the threshold on the surface as well as on screen.
Gain – Use this to increase the volume of the compressed signal to boost the level back up. Check this by taking the compressor in and out of the signal chain and making sure the levels are the same.
RMS/Peak – RMS mode looks at the average of a signal, Peak mode looks at the peak of a signal.
Attack – How fast the compressor acts when the signal passes the threshold.
Release – How long it takes for the compressor to stop acting after the signal drops below the threshold.
Soft knee – Changes the ratio so that is compresses the signal smoothly.
Side chain - Trigger the compressor from itself, or any input or output channel. Press the filter in to activate a High Pass Filter, Low Pass Filter or Band Pass Filter mode to get a more accurate trigger from the source.
Parallel Path – This can be used to mix in some of the uncompressed signal with the compressed signal. Press the Parallel Path button to activate.
Mix Ext In
To route an external input straight through to an output bus, assign the source from any source. This allows for coms systems and anything you wouldn’t want to use an input processing channel up for.
This 28-band stereo graphic EQ is a useful tool which can be used to tune PA systems and monitor systems to shape the tone of the speakers to taste, and prevent the possibility of feedback. Each frequency band has a fixed width of 1/3 of an octave, allowing +/- 12dB on frequencies ranging from 31Hz to 16kHz.
When tuning a PA, it is possible to use a reference piece of music that you are familiar with to make the system reproduce the track in a way you expect it to sound. Frequency analysis and measurement software can be used, in conjunction with a reference microphone, to shape the system to a flatter frequency response. It is always best to use your ears for judgement, but in most cases a combination of musical and measurement tuning can give great results.
When a mix is selected, press the GEQ fader flip key to view the GEQ frequencies on the faders. This will show the GEQ frequencies from 31.5Hz to 6.3kHz, press the fader flip key again to view frequencies from 80Hz to 16kHz. To reset a single frequency back to 0dB, press the select key for that frequency. To exit fader flip mode, press the fader flip key again.