Sunday, 25 October 2009

Mixing Desks

Definition Of The Mixing Desk; The mixing desk brings multiple sound source's/signals together to be mixed.

There are a few different types of mixing desks, Inline, Live, Split, Broadcast, and Matrix.
We shall take a look at each different type of mixing desk.

Inline Desk;

Inputs/Outputs and Monitor section are all in line (All in one channel strip).

In Record mode the channel fader receives mic or line input, and the monitor section receives the tape returns.

In Mixdown mode the channel fader receives the tape returns, and the monitor section receives mic or line input. Basically vice-versa of the Record Mode situation.

Here are a few things that can be found in each specific section of an inline mixing desk.

Input Section;
Pan, Phantom power, Attenuate Switch, EQ, Unity Gain, Mic/Line Switch, Phase Reverse, etc.

Output Section;
Channel fader, Multitrack Assign, L+R Assign, etc.

Monitor Section;
Pan, Solo, Mute, EQ, L+R Assign, Output to Tape, Tape Return signal (Lets you monitor what is coming from tape), Monitor Source Select, Monitor fader, etc.

Master Section;
Master Source Select (Level of what you are listening to), Headphone source, Control room level, Auxiliary master level, Separate headphone level, Oscillator (Generates a tone to calibrate external devices such as a tape deck meter, compact disc meter, DAT machine meter, etc.) Master Fader (Controls the level going to the 2 track mastering device/s), Talkback microphone (For Communication to the live room, etc.), Auxiliary Master 1+2/3+4.

Benefits and Use's;
Can come in a wide variety of sizes from big to small, they are very versatile, and are mostly used in professional and home built studio's.

Behringer MX-9000, Behringer MX3242X Eurodesk, Soundtracs JADE

Live Desk;

A Live desk has no monitoring section or no tape return's.
It has got an input section, an output section, an auxiliary section and has group faders.
It only has one mode so record mode is the same as mix. So basically what you would be hearing live is what you would be recording.
Benefits and Use's;

A live desk is exactly that, it allows you to record exactly what you are mixing/hearing, it is used for live PA's at festivals, live gigs and concerts, etc.
They are usually pretty basic, and straight forward to use.


Samson L2400, Allen and Heath G4800-824B, Mackie Onyx 32.4

Split Desk;

On a Split Desk the monitor section receives the Mic and Line feeds (Returns).

In Mixdown mode the channel inputs will be receiving the tape returns.

On a split desk the inputs/outputs on the monitor section are separate with the inputs on the left and the outputs and the monitor section on the right.

Benefits and Use's;

More complex than an inline mixing desk, also a lot bigger than an Inline mixing desk and are mostly used in the more professional studio's. They are also very expensive to buy.


Studiomaster Mixdown Classic 8

Broadcast Desk;

Is very similar to a DJ's mixing desk, and it is very basic and easy to use.
Benefits and Use's;

Usually lightweight, very basic and easy to use. They are mostly used in Television studio's, Night clubs, etc.


ADT-Audio BC3, ADT-Audio 5MT,

Matrix Desk;

Designed basically to give individual monitoring on stage, So that each musician can be provided with there own monitor mix.
Benefits and Use's;

Mostly used for live PA's at festivals, concerts and gigs, etc.


Behringer MINIMON MON800, Samson C-control, TOA M-900

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Signal Flow

The following tries to demonstrate how the signal flows from the sound source, e.g. Synthesizer into the mixing desk, through the mixing desk via EQ, etc, to the tape machine, and back again.

Mixing Desk

Input - e.g. Synthesizers, Drum Machines, Microphones, etc. Get plugged into the input section.
Insert Point - e.g. Send & Return for dynamic effects units such as compressor's, noise gates, etc.
EQ Section - e.g. Changes the harmonics and the tone of the signal. At the EQ section.
Solo Channel - eg. Overrides' all other functions and listen's to the signal at this point on the desk.
Auxiliary Channel Send - e.g. Sends the signal to the auxiliary master.
Channel Fader - e.g. Controls the channels level going to tape.
Tape Assign Section - e.g. Assigns specific channels on the desk to specific channels on the tape machine.

Tape Machine
Tape In - e.g. Signal going into the tape machine.
Tape Out - e.g. Signal coming out of the tape machine.

Mixing Desk
Tape Return Button - e.g. Visually monitor the signal coming back from the tape machine.
Monitor EQ - e.g. EQ the signal in the monitor section, for monitoring purposes, etc.
Monitor Fader - e.g. Monitor the signal coming back from the tape machine.
Left & Right Main - e.g. Controls the overall level going to the 2 track mastering device.

*The insert point allows a dynamic signal processor directly into the channel.

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Setting Unity Gain

Unity gain simply means that the gain stage is neither boosting nor attenuating the signal. It is, in effect, multiplying by one, unity. As a concept, unity gain represents the right philosophy for making the best use of dynamic range (avoiding noise at low levels, but avoiding distortion at high levels), but the equipment designers have to share this philosophy and layout the equipment and label all the faders and pots and sliders accordingly.

The key is to read the manual and figure out the settings necessary for your particular piece of equipment to be at unity gain. Then, if a 0.775 volt signal goes in, it will be 0.775 volts going out.

Here is a brief run through, of how to go about achieving unity gain on an inline mixing desk.

1) Select mic or line level.

2) Solo the channel.

3) Set unity gain by adjusting the gain pot to;

-4dB to 0dB, if you are using Volume Unit Meters (VU).

0dB to +3dB, if you are using Peak Program Meters (PPMs).

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