Glossary - Mixer terms
The Access Send/Receive connections are connected to the Patchbay. They are normalized (connected) and looped back to the Receive connections at the patchbay.
 
They are a tap into the input module strip before the signal gets sent on to the EQ, Aux Outputs and Output Fader sections.
 
It can be used as a separate injection point for an external device like an effect unit, EQ, compressor, etc. This is also know as an INSERT point since you can insert an external piece of equipment at this point, in series with the signal path.
AUX A and B Send
In addition to being able to assign a selected input signal to eight different busses (found below - Output Buss Selector) which feed the tape recorders, there are two effects busses labeled AUX A and AUX B for additional routing to external processing equipment.

   See Aux Send Detail.  
The Equalizer section of the M50 mixer has three semi-parametric controls. Hi-shelving, MID and Low-shelving.
 
Each of the three EQs actually consists of a set of concentric controls; one for Gain/Attenuation and one for frequency selection. The semi-parametric designation is due to the lack of a "Q" control; a bandwidth control found on many EQ systems.
 
Below these controls is a red LED (Light Emitting Diode) to indicate whether the EQ is engaged or not. This is actually indicated as a "Bypass" switch on the schematic. When the EQ is muted (bypassed), the LED is on.
 
The Input Selector Switches (one external, one internal) is used to select the source of the signal that will be used through the input strip.
The MIC position is used only in input strips 1 & 2 at the moment since they are the only two that are connected to microphones. There is also an associated Phase switch used to reverse the phase of the microphone signal.
 
The LINE position is used for all the samplers, computer audio, FX returns, etc; everything except the tape recorder returns.
 
The RMX (remix) or TAPE position on the selector switch selects only tape recorders. These inputs are also know as the tape recorder returns; these are the 8 track recorders (1-8), DAT A is 2 trk A (9 & 10), and 2 trk B (11 & 12) may be either another DAT deck or a 1/2 track analog recorder.

 

 
There is a line trim pot for these inputs, separate from that used for mic trim of microphone levels.
 
Notice the selector switch's positions. Trace the path the signal takes through the line trim pot to the input selector switch.
1) Microphone
2) Line
3) Remix (RMX) Tape Decks
The switch is also internally connected to another switch (indicated by the dashed line).
This allows for a separate trim (gain/attenuation) for the mic and line inputs; the RMX is a Line input.
Input Trim
The input signal level is further adjusted using this input trim.
It consists of two concentric rotary pots.
The outside ring is for adjusting the microphone primary input level,
and the inside knob is for primary line and tape input level.
 
This trim should be adjusted with the input fader slider and Buss Master faders positioned in the gray shaded area of the fader indicator.
 
This will give the best signal quality through to your recording medium. Physically this means that the majority of your mixing, movement of the faders below the gray, will be some form of attenuation; an attenuation of noise, hiss and other unwanted signals.
 
Typically, line and tape remix levels are set with the inner knob at about the 1:00 to 3:00 position.
Level is the final output level of the input signal as it goes to the mixer matrix. This is also the volume control for the Direct Out connection from each input strip. This output is fundamental to the sound projection system for the ÉuCuE concert Series.
 
Line Input connectors are used for audio level inputs such as effects units, synthesizer outputs and tape recorder outs. In this latter case though, there are separate Tape Inputs normalized at the patchbay for the tape recorders in the studio.
 
Browse through the Fostex Patchbay Stack for more information and a diagram about the patchbay normalized Line Input connections.
The Line Trim pot adjusts the initial input level coming into the input module from either the Tape returns (RMX) or the Line input.
Set the average level to 0 VU when the input fader is set in the gray shaded area.
This is a separate trim from the mic input trim.
Microphone Attenuation is sometimes necessary to avoid input stage distortion. This occurs when the audio source volume is greater than the ability of the trim attenuator to bring it down to reasonable levels.
 
This attenuator is a 30 dB PAD (P) or resistance. An example of it's use would be when miking a drum set where the amplitude of the snare is too loud even with the trim set at 0.
The Microphone Inputs on the mixer are of an XLR or "Cannon" type connector and are found at the rear of the mixer. This is the only place for a microphone level signal to go into the mixer.
 
Microphone signals need amplification and/or attenuation depending on the signal strength coming from the microphone and the kind of microphone.
 
NOTE: Remember that if a microphone source is taken through the mic inputs of a tape recorder, this signal is no longer at the mic level and should therefore be patched as a line level signal; a normal tape out in this case.
The Mic Trim pot (potentiometer) is used to give fine adjustment to the input gain of a microphone signal.
 
The Mic Trim should be adjusted to give an average signal strength of 0 VU when the input fader is set in the shaded area of the fader slider.
see SHADED area.
 
The Mute switches for the AUX A and B sends are ON when the red light is ON. They turn off the Aux send function for that module. Leave these ON (Red ON) so that no stray signals (ie inadvertant) get nto the effects send pathway.
 
The Output Buss Selector is where the real mixing function of a mixer takes place. Each of the inputs may be mixed to any of the outputs by assigning the output through these switches. The M50 has 8 output lines or Busses. There are 8 selector buttons which correspond to these 8 busses. Any combination of one or more outputs may be selected.
 
The selector buttons are arranged in odd/even rows. This facilitates panning between these pairings. More information on Buss Outputs.
 
The Overload light indicates that the signal input strength is near or at distortion levels. It is set by the manufacturer to light when the signal is too high for the input module electronics. If this light just blinks occasionally, use it as a warning that you are at the threshold of distoring the input system. A steady light indicates some level of distortion is occuring.
Panning is accomplished by a 'Pan Pot", a Panoramic Potentiometer, found below the Output Buss Selector. It adjusts the relative audio signal strength being sent to odd/even output pairs.
 
Phantom Power is used for condenser microphones such as the AKG 451 and 414.
 
The "condenser" element of this type of microphone operates only when a voltage is applied. This voltage is most often supplied by an external source, thus the "phantom" designation.
 
The Phantom switch on mixer input #1 is always left ON. It is found at the rear of the M50 mixer and is not accessible to studio users.
 
Phantom power should be disengaged for "dynamic" type microphones to avoid damage when the phantom voltage is applied to the dynamic coil element.
The Phase switch is used to invert the signal phase of a microphone input.
 
It is used if a cancellation of frequencies is perceived between two or more mic inputs. This "phasiness" can be caused by faulty wiring or poor placement of two or more mics with respect to each other. A loss of low frequency when "mono"ing a mix is often a sign of an out-of-phase signal in the mix.
 
This switch is infrequently used in the Electroacoustic studio as more than one mic is seldom used.
The Pre OUT connector for each input module of the M50 is connected to the Fostex Patchbay.
 
This output is a tap out of the input module before the signal gets to the EQ (pre-EQ), Aux Outputs and Output Fader sections.
 
It can be used as a separate feed to an external device.
Tape Inputs also know as RMX (remix) inputs are usually designated for use of incoming tape recorder signals. The studios are set in this manner.
 
You may also insert any Line Level signal into these inputs and visa versa. They are provided for extra ease of access to studio equipment.