Saturday, February 25, 2012

MTA 980 Console!

Assessments and more assessments. Yeah, here we go!


First, let's start with Impedance. There are 2 kinds of impedance: High and Low. Impedance is the resistance to the flow of current and is measured in ohms. High impedance has high resistance from 10,000 to 20,000 ohms. Low impedance has low resistance about 150 to 1000 ohms. The best way to understand impedance is to think of a water hose. A lot of water being sprayed out of a small garden hose into a drain pipe will have no resistance and the small, high impedance hose is spraying into a big, low impedance drain causing distortion. The other way around causes low signal. 

Here are some typical equipment levels:

  • Microphone - about 0.002 volts to 1 volt depending on the mic.
  • Instrument - about 0.1 volt to 1 volt for passive acoustic guitar pickup and to 1.75 volts for active.
  • Semi-pro, or consumer Line - -10 dBV, or 0.316 volts.
  • Pro Line - +4 dBV, or 1.23 volts. 
To connect a high-impedance instrument to a low-impedance amplifier, you use a direct box, or a line matching transformer, impedance matching transformer, or DI Box (direct injection box).

Before the signal reaches the EQ's, it can toggle between mic and line level, but mic level is at line level due to the mic preamps.

The mic preamp is a small amplifier circuit normally at the top of the channel strip. The preamp level controls how much of the incoming signal is amplified. Other names for the mic preamp are mic gain trim, input preamp, trim, preamp, or gain.

The signal passes through the microphone before it hits the mic preamp. When it does hit the preamp, the signal must be at mic level, or the level that the microphone "hears", which is about 30 to 60 db. Then, the preamp can boost the signal to line level. Because mixers work at line level, the mic level must pass through, and be amplified by the mic preamp before the signal can continue on its course.

Though the mic level must be amplified through the mic preamp, we want to use as little mic pre-amplification as possible to reduce the noise it makes when it feeds the signal back into itself. This noise is also amplified--amplified self-noise.

Frequency ranges within each level of the EQ:

<-------- The High Frequencies range from 1,000 hz to 15,000 hz

<-------- The High Mid Frequencies range from 700 hz to 10,000 hz

<-------- The Low Mid Frequencies range from 150 hz to 2,000 hz

<-------- The Low Frequencies range from 40 hz to 650 hz

<-------- Boost or cut EACH by 15db with the right lower knobs

<-------- High Pass Filter at 50 hz
<-------- Pushbutton allows the EQ to be switched in or out of the circuit

Next, the signal hits the Inserts. Something crucial to understanding the difference between Inserts and Sends is that inserts are NOT variable, there is NO percentage of signal sent to them, they are either ON or OFF, 100% or 0%. This is called dynamic processing which includes:

  • Gates
  • Limiters
  • Expanders
  • Compressors
Next, the signal hits the phase option (little hollow circle with slanted line through it). 

Then, to the Auxiliary Sends all the way down to Aux 1, Aux 2, Aux 3, Aux 4 (Mono), Aux 5-6, and Aux 7-8 (Stereo). 

Next, comes the PFL, or Pre-Fader Listen. The name is pretty explanatory. Then, the Fader - The linear, variable, volume knob on the bottom of the channel strip. 

And on to the Mutes and the Solos. 

To the Direct Out. 

To the Pan rotary knobs. 

Then, to the pointless AFL, After-Fader Listen. Whatever that means. 

On the Post Channel Strip, the signal can go through the Group Bus, the Remix (Mix Output), the Solo Bus, Auxiliary Bus, PFL/AFL, and Auto-Mute Bus. 

This is the Monitor Module. The EQ's are the same as the input modules without the 50 hz HPF. 

<-------------- 4 of the possible 8 Auxiliary Busses are available. Aux 1 and Aux 2 are mono and Aux 5-6 is Stereo. 

<--------------- Monitor Level and Pan are here with a rotary level control and a center detention pan pot routes the modules output to the monitors OR through the remix groups when the MIX button is pushed in. 

The Echo Returns are the same except for the bottom half with the Return Level, Pan, Solo, and Mute. 

The Auxiliary Master Module is a little different from the Monitor and Echo Returns Modules.

Studio playback sends monitored signal (Aux 5-6/Aux 7-8) to studio ------->
Solo Master - Rotary potentiometer adjusts the control room monitor level of the stereo PFL/AFL solo signal ------------------------------------------------------>

Alternative Speaker Switch ----------------------------------------------------------->

<-------------- 8 Auxiliary Master Level controllers, each with solo and master mute.
Control room master functions with 4 stereo sources to the control room speakers, MIX - switches the control room speakers from monitoring to 24 multitrack groups to the stereo remix outputs, DIM - attenuates by 20db, and MUTE - kills the control room monitor signal ------------------------------------>
The Auto-Mutes masters that can be pre-selected on the input modules ----->

Talkback - built-in electret mic and level control to route your voice to the mono Aux 1 or 2, or the stereo Aux 5-6 or 7-8 ------------------------------------>
<-------------- Down at the bottom, there is an oscillator with the options 50 hz, 100 hz, 1,000 hz, and 10,000 hz. 

Here is the layout from the MTA Console of the signal flow for each input module. 

The Assessment on this is going to be hard :( Hopefully, I am grasping this because you never know what is going to go through your head come test time. 

Anyways, I am getting a lot of really great experience working with Kory on some of his Capstone Project and singing for the baseball games!

1 comment:

  1. Nice to see the MTA 980 get some love. I built and tested these with Malcolm back in the 90's. Good times :)