Preamp

The Preamp page provides access to the Input Channel source patching, socket Preamp settings, and channel Trim and HPF.

Touch a control box to highlight a parameter then turn the screen Rotary to adjust its value.

Socket Source – Open the drop-down menu to choose which source to patch to the channel. Touch Apply to accept or Cancel to leave unchanged.

Source patching options:

• Unassigned
• An AudioRack input (via dSNAKE)
• A GLD rear panel input
• An I/O Port input
• The USB stereo playback
• One of the built-in effects (Rack FX)
• The Signal Generator (as a test source)
• Any Group, Aux, Mains, Matrix mix output

To provide a simple starting point the Template Show default is one-to-one mapping between input sockets and channels. For example, Socket 1 to Channel 1, Socket 2 to Channel 2 and so on.

Socket Preamp – If the patched source is a Mic/Line XLR input then its Preamp controls are shown. These provide remote control of the input preamp circuit located at the socket.

Gain – Touch to highlight the Gain value box. Turn the screen Rotary to adjust.

Phantom power - Touch and hold the 48V button for 1 second. This is to prevent accidental operation.

Pad switches in a 20dB input attenuator. The combined Gain+Pad value is shown in the Gain box.

Preamp Safe – Touch this button to make Preamp Gain Pad and 48V settings safe from Scene recall. This can be useful when splitting the same mic preamp to two or more channels.

Note Making a channel Safe using the surface Safe key also makes the associated Preamp safe from Scene recall. Turning off Safe using the surface key also unsafes the Preamp.

Trim can provide +/-24dB ‘gain’ control when the source does not have a preamp, for example input from GLD surface RCA line inputs, the I/O Port or USB playback. Trim is part of the channel, not the preamp.
When working with mic preamps it is typical to leave Trim set to 0dB unless you are gain sharing and want to adjust local level independent of preamp Gain.

Polarity toggles normal and reverse (+/- balanced input pins swapped). Use to compensate for reverse wired cables, or when double miking sources such as a snare drum with ‘top’ and ‘bottom’ mics, or kick drum with ‘in’ and ‘out’ mics. Polarity is part of the channel, not the preamp.

HPF – The High Pass Filter cuts low frequencies, for example to reduce pops or wind noise on microphones or tune out unwanted low end on acoustic instruments.

The HPF cut-off frequency can be adjusted from 20Hz to 2kHz. There is an option to set its slope can be set to one of 4 settings:

• 12dB/Octave Butterworth
• 18dB/Octave Butterworth (Reset default)
• 24dB/Octave Butterworth
• 18dB/Octave Bessel

The Bessel filter has minimal phase distortion and optimised transient response at the cost of relaxed roll-off in the knee of the slope.

The filter can be switched in or out of circuit. A good starting point for vocal mics is to switch the HPF in and set to around 120Hz.

The HPF can also be viewed and adjusted in the PEQ page.

Screen Sel buttons – These do the same as their related surface Processing Strip Sel keys:

• Hold to listen to (PFL) the signal at that point
• Use with the Copy/Paste/Reset keys

The Preamp Option lets you choose whether the Processing Strip Gain rotary controls the Preamp Gain or channel Trim.

• Preamp on Surface – The surface Preamp rotary adjusts Preamp Gain. This is the default for normal single console operation.
• Trim on Surface – The surface Preamp rotary now adjusts Channel Trim. Consider using this in situations where you are sharing the same Preamp between channels or FOH and Monitor consoles.

OPTIONS pull-up window

Provides a global setting for Preamp or Trim on Surface. This affects all input channels.

Touch the pull-up tab and swipe your finger upwards to open its window.

A note about Gain Sharing

Any Preamp can be patched to any Channel. The same Preamp can be patched to more than one channel. For example:

• One set of channels within the GLD allocated to the FOH mix and another split from the same mic inputs for important channels feeding the monitor mixes.
• Mic preamps split between dedicated FOH and Monitor consoles using a digital snake connected to the GLD I/O Port.

In the above cases the Preamp is shared by two channels. The ‘Master’ console has control of the preamps and mic Gain. The ‘Slave’ console gets its inputs from the digital split. Its surface Preamp rotary becomes Channel Trim as it does not have mic preamps. However, it will be affected by preamp Gain changes made at the Master.

A solution is to set the Preamp Gain during sound check and for both engineers to use the Trim rather than Gain controls during the show. This means setting the ‘Trim on Surface’ option on the ‘Master’ console.