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SOUND 1
Michael Drolet -- 2018

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SOUNDCRAFT SIGNATURE 22 MTK MIXER


           


INTRODUCTION:

There are many terms used to refer to the complicated-looking piece of electronic gear sitting on the table in front of the Sound Booth window:

console, mixer, mixing board, sound board, mixing desk, sound desk.


[I will try to be consistent and to always refer to the mixer.  If  I slip up, you now know the other possible terms.]

In a production studio, the mixer is used to send sound signals from various sources, (microphones, CD players, FX units) to various destinations (usually tape machines, hard disk recorders or FX units). It can also be used to modify the tonal quality (EQ) or relative balance of the sound signals passing through it.

In a performance space, the mixer serves to send the various sound sources (microphones, CD players or FX units) to various loudspeakers on the stage or throughout the house. It allows you to control where the sounds will be heard and how loud they will be.

The same mixer will generally serve for either the production studio or performance space.  One of the mixers we have at John Abbott is a  SOUNDCRAFT SIGNATURE 22 MTK, designed in the great Britain and manufactured in China. It is representative of mixers you will find in many production studios or theatre spaces today. 

SIGNATURE 12

SOUNDCRAFT SIGNATURE 22 MTK MIXER:

In a sound system, a source of sound is referred to as an output.  A destination is referred to as an input.   Building a sound system involves connecting sources to destinations  --   an output to an input to an output to an input.....and so on.

  • The sources could be the outputs of mics. on stage, CD players,  effects units or tracks from a computer.
  • The destinations could be the inputs of the House speaker system, onstage monitors, headphone amps or effects units.

The SOUNDCRAFT SIGNATURE 22 MTK mixer allows you to simultaneously control and send, any (one or more) of twenty-two sound sources  to

  • any of four intermediate destinations; the GROUP outputs, and/or to
  • either of two main destinations; the MASTER outputs, and/or to 
  • one or more of  five auxiliary destinations; the AUX1-5  outputs.

In a sort of technical short-hand, this mixer may referred to as a 22:4:2 mixer (with 5 auxiliaries) to indicate it offers 22 inputs, 4 group outputs, and 2 main outputs (with 5 auxiliaries).

Although the mixer may appear to be complicated, it is in fact, composed of only a few different building blocks, called modules  or strips.  Each type of strip groups together all the controls and internal circuitry to perform similar functions.

On this mixer, there are two kinds of  INPUT strips, 14 MONO and 6 STEREO.  The INPUT strips are grouped together on the left side of the mixer.  The  AUX/GROUP/MASTER strip is on the extreme right.

You will only need to learn the operation of these few strips, 

  • MONO INPUT 
  • STEREO INPUT  (3 variants)  
  • AUX/GROUP/MASTER OUTPUT
in order to "master" (sorry) operation of the entire mixer.

We'll have a look at the front panel controls and the signal flow through each of the modules in turn.



------------------------------------   INPUTS   ---------------------------------- OUTPUTS
MONO STEREO
CHANNELS 1-14  CHANNELS 15-18 CHANNELS 19-20 FX RETURN AUX/GROUP/MASTER
Mono Input STEREO INPUT
STEREO INPUT LINE SIGNATURE 12 FX RTN SIGNATURE 22 MASTER
CHANNELS 1-14 CHANNELS 15-18 CHANNELS 19-22 FX RETURNS AUX/GROUP/MASTER
MONO STEREO
------------------------------------   INPUTS   ---------------------------------- OUTPUTS


MONO INPUT STRIP



MONO inputs are used to connect to sources with a single output -- microphones, guitars.




Audio signal levels can  fall into one of two broad categories.


  • Microphone level signals.  --  Microphones, electric guitars and other electronic instruments generate very low level signals; on the order of a few millivolts -- thousandths of a volt.

  • Line level signals. Tape recorders, CD players, FX units and most other professional studio equipment, all generate much higher signal levels -- several tenths of a volt or more.
There is a difference of 40 or 60 decibels (dB) between microphone level and line level signals.

Microphone level signals connect to the three-pin XLR-type female connectors.

Line level signals connect to the 1/4 inch TRS jacks.


Either type of signal must be connected to the mixer via the appropriate jack or socket, tp avoid undesireably deteriorating the quality of the signal.
  • Connecting a line-level output to a mic-level input will result in distortion.
  • Connecting a mic-level output to a line-level input will result in an unusably low (quiet) signal.
DO NOT connect active signals to both sockets on the same input channel.


SIGNATURE_12_MONO_INPUT_SOCKETS

SIGNATURE_12_MONO_INPUT_GAIN_HIGH_PASS_USB_RTN
GAIN/100 Hz/USB RTN

The GAIN control allows you to adjust the input strip so that you can operate with the white channel fader in its normal range, around -0- on the scale
-- no amplification. This assures that the signal will have the maximum headroom and minimum noise.  (See PFL button below.)

Headroom is the level difference available between normal level and the point of distortion.

Noise is the background hiss you hear when you turn the gain or volume up too much.
The GAIN control is the most important  setting on the console.  
  • Set it correctly, you have the best possible chance of getting good sound. 
  • Set it incorrectly, and nothing you do to the signal later in the audio path will fix it.

The 100Hz (High Pass --  Low Cut Filter) button allows you to remove unwanted low-frequency noise from the input signal.
  • It cuts sharply (@18dB/octave) below 100Hz
  • It can be used to cut traffic or air conditioning rumble
  • Don't use this filter on bass guitars or tubas.
The USB RTN (Universal Serial Bus Return) allows you to choose between the analog channel input and the digital signal from a computer.
LIMITER

The LIMITER button will engage a simple automatic gain control on the channel.  The brightness of the LED indicates the amount of gain reduction being applied.

The LIMITER function is only availble on MONO Input Channels 1-8.
SIGNATURE_12_MONO_LIMITER
HI-Z
The HI-Z  button causes the LINE TRS jack to appear electrically similar to the input jack  on a guitar amplifier.  This can allow you to record an instrument like an electric guitar by conneting it directly to the console.

The HI-Z  function is only availble on MONO Input Channels 7-10.
SIGNATURE_12_MONO_HI_Z
EQUALISER
The EQ (EQualiser) section of the input strip allows you to adjust the tonal qualities of the input signal.  The EQ is to sound, what coloured "gels" are to lighting.
High EQ HF: (High Frequency) 
 Shelving
  • boost or cut 15dB @ 12kHz
SIGNATURE_12_MONO_EQ
MID EQ HMF: (High Mid Frequency)
  • boost or cut 15dB
  • variable  centre frequency from 400 Hz to  8.0  kHz
MID EQ LMF: (Low Mid Frequency)
  • boost or cut 15dB
  • variable  centre frequency from 80 Hz to  2.0  kHz
SIGNATURE_12_MONO_LOW_EQ

LF: (Low Frequency)

 Shelving
  • boost or cut 15dB @ 60Hz
AUXILLIARY SENDS 1-5
 

The controls labeled AUX (AUXilliary) allow you to send a part of the signal from any input channel strip to any of three additional outputs. These outputs can be used to feed a separate mix to program sound, monitors onstage, headphones in the studio, or to the sound processing and effects devices in the control room.

AUX sends can be taken before or after the channel fader.  We call these feeds PRE fader or POST fader. 

POST fader sends are used to feed reverb devices where you would want the strength of the reverb effect to follow the level as controlled by the channel fader. 

PRE fader sends are used to feed headphones or stage monitors. You wouldn't necessarily want the mix in the headphones to change as you adjust  the recording or house levels.

On the SIGNATURE 22 MTK:
AUX 1-5  sends can be switched to be either PRE or POST and used to feed external equipment.  (see AUX MASTER below.)

AUX 4 and 5 sends are used to feed the internal Effects Processors, POST fader, as well..


SIGNATURE_12_MONO_AUX_SEND
 
PAN/MUTE/PFL/CHANNEL FADER

The PAN control (short for panoramic potentiometer) allows you to send the signal  anywhere in the sound field between the selected left and right outputs.
The MUTE button cuts-off (mutes) the input signal from the selected outputs.
The PFL (Pre-Fade Listen) button sends the input signal directly to the left/right LED meters and the headphones.  A red LED (AFL/PFL ACTIVE), just below the meters indicates that at least one PFL button is pressed.

With PFL pressed on one input channel, start with the GAIN control fully counter-clockwise.  As someone talks into the microphone or while you play the loudest cut of your show CD;  rotate GAIN  until the meters are just reaching  the -0- dB point.  They should never go higher than +6

Don't forget to release the PFL button afterwards! 
If you press the MST (MaSTer) button and pan fully left; the signal will go only to  the left MASTER output.  Panning right will assign the signal to only the right MASTER output. Midway between left and right will assign the signal somewhere between.

Odd numbered inputs and outputs are arbitrarily considered as left and the even numbered ones as right.

If you press the 1-2(GROUP 1-2) button and pan fully left; the signal will go only to  the GROUP 1 output.  Panning right will assign the signal to only the right GROUP 2 output. Midway between left and right will assign the signal somewhere between.


The sliding control with the white marker is the input channel fader. This is your operational control over the signal level during a recording or performance. It allows you to smoothly fade an individual sound in or out.

At the -0- setting of the channel fader, there is still 10 dB of gain available, should the input signal drop in level. We say that there is 10 dB of gain-in-hand. This gives you room to maneuver should the input signal change.

Working at -0- on the channel fader also allows for smooth fades in or out.


SIGNATURE_12_MONO_ROUTING


STEREO INPUT STRIPS


On the SIGNATURE 22 MTK, input channels 15/16 17/18, 19/20 and 21/22 are STEREO input channels.

STEREO inputs are used for sources with a left and a right output -- CD or DVD players, keyboards, effects processors or computer audio outputs.  A single fader controls the level of both left and right  channels of the source.

STEREO channels 15/16 and 17/18 have a 3-pin XLR connector to accept the output of a microphone.  The  microphone signal is sent to both left and right inputs.  They have a pair (left/right) of TRS sockets to accept a left and right line level source.







SIGNATURE_12_STEREO_INPUT_SOCKETS
STEREO channel 19/20 has no microphone level input, and the line level input is on a pair of TRS sockets.

Alternatively, the input could be from USB RTN channels 19/20.
SIGNATURE_22_STEREO_TRS_SOCKETS
STEREO channel 21/22 has no microphone level input, and the analog line level input is on a pair of RCA sockets.

Alternatively, the input could be from USB RTN channels 21/22.

SIGNATURE_12_STEREO_RCA_SOCKETS
On the SIGNATURE 22 MTK, what you might think would be input channels 23/24 and 25/26 get their signal from the internal effects processors, and are labelled FX RETURN 1 and 2.

Because the source is internal to the console, there are no input sockets.

Most of the other controls on a STEREO Input strip are identical to those on a  MONO Strip.  Two exceptions --

  • the PAN control on a STEREO channel is called BAL (BALance) but serves the same function.
  • the EQ on a stereo channel  is simpler, having only one parametric band, not two.


AUX/GROUP/MASTER OUTPUTS
SIGNATURE_22_MASTER SIGNATURE_22_OUTPUT_CONNECTORS
AUX MASTER STRIP
The AUX1-5 MST (MaSTer) controls set  the level of signals sent to the AUX1-5  SEND busses and to the AUX 1-5  TRS output connectors.

The  PRE/POST button allows AUX SEND to be sent either PRE or POST (fader).

The AFL (After Fader Listen)  button allows you to SOLO any of the AUX SEND busses.

.
SIGNATURE_22_AUX_SEND_MASTERS SIGNATURE_22_AUX_SEND_MASTER_OUTPUTS
GROUP MASTER STRIP

The GROUP 1-2 faders set the level of signals sent to the GROUP 1  and GROUP 2 busses, and to the GRP1 and to the GRP2 TRS output connectors.

If you want to use the GROUP 1-2 faders as SUBGROUPS (or Sub Masters), pressing the corresponding MST button, will send the signals on to the Master buss.

The MONO button will cause the
GROUP 1  and GROUP 2 buss signals to be mixed to mono before being fed to the Master bus.
SIGNATURE_22_GROUP_FADER
SIGNATURE_22_GROUP_OUTPUTS
MASTER STRIP

The MASTER fader sets the level of signals sent to the Master  buss, and to the MST L and to the MST R XLR output connectors.

The INTERVAL MUTE  button will mute all input channels except STEREO Input channel 21/22.
SIGNATURE_22_MASTER_FADER SIGNATURE_12_MASTER_OUTPUTS
METERS

The meters on the Signature 12MTK show Master Left/Right output level in normal operation.

If a SOLO (PFL or AFL) button is activated then the meters will display Solo bus levels.
When any SOLO button on the console is depressed, the "AFL/PFL" will light to indicate this condition.

Check this LED if the headphone/monitoring output is not as expected.
SIGNATURE_12_METERS
HEADPHONES
The headphone signal is always the Master Stereo Output unless a Solo (PFL or AFL) is activated.

In that case, the headphone output is switched to the Solo Bus.
SIGNATURE_12_HEADPHONE_LEVEL SIGNATURE_12_HEADPHONE_JACK
USB POWER
This USB Type-A socket is for attaching a USB-powered LED lamp - NOT for recharging your phone.
SIGNATURE_12_USB_POWER
GLOBAL PHANTOM POWER

Some condenser or electret type microphones can be powered externally, eliminating the need for batteries. The power required can be supplied by the mixer via the same cable used to carry the microphone signal to the mixer. This system is called phantom powering.

The  "48V" LED indicates that 48 volt PHANTOM POWER has been applied to all of the microphone sockets by the "PHANTOM POWER" button.

In certain cases, supplying 48 volt power to a microphone or instrument not requiring it , may result in noise or hum (at best) or damage to the microphone or instrument (at worst).

Phantom powering should only be activated if you know you need it for a given device.

SIGNATURE_12_PHANTOM_POWER


ADDITIONAL LINKS



Soundcraft Signature -- Lexicon Effects --  Notes on the Soundcraft Signature built-in FX Processor

Soundcraft Signature 12 MTK -- Owner's Manual -- Read this attentively to really understand the mixer's operation.

Soundcraft Signature
 MTK --  Recording Guide -- How to use the USB sound device on both Signature 12 MTK and 22 MTK consoles.