MBI 24 Owners Group
M01

M01 Mono line/microphone channel (images)


Version with EQ designated M02.
P version with group selection.
B version without group selection.

Connections


  • XLR - Mic input
  • XLR - Mono line input


  • Type B jack - insert points - optional. The insertion points are balanced, with tip hot, ring cold, sleeve ground. The return socket is normalled to the send signal.



Jumpers and settings


Switches on rear


  • Mic/Line - to select whether the mono line input or mic input are conntected
  • Phantom power - which switched on, 48VDC phantom power from the main power supply is supplied to the mic socket (pin 1 is ground, pins 2 and 3 are +48VDC each via a 6k8 resistor)
  • Mute mode - distant/off/local - selects which mute buss is pulled to ground for muting - normally local


Jumpers on board


Image showing location of jumpers here
  • P1 - line mute mode - normally "open" so that there is no muting when the channel is in line mode (so muting is only performed in mic mode), but can be jumpered closed to provide muting for mono line inputs


  • P2 -Connection where optional EQ is connected (in M02 channels). In M01 channels, the terminal pins may not be present, and there'll just be a series of holes in the PCB.

    Pin 1 is to the bottom of the above image, and the connections are: 1 NC, 2 Gnd, 3 mono output to EQ cut switch, 4 -16V, 5 NC, 6 +16V, 7 mono input from V12 (post insertion point).

  • P3 - Pre-fade stereo option for aux 3 and 4, where aux 3 becomes left and aux 4 becomes right, instead of two mono feeds from IC5b. Shown in stereo mode below.
  • P4 - Post-fade stereo option for aux 3 and 4, where aux 3 becomes left and aux 4 becomes right, instead of two mono feeds from IC5a. Shown in stereo mode below.


Controls


  • Fine/coarse gain

    Fine control is the top of the dual knob (RV1b, 10k linear), Coarse control is the lower ring part of the dual knob (RV1a, 47k reverse log).

  • EQ (M02 only)
    • High end shelf at 10kHz
    • Tunable peak between 400Hz and 6kHz
    • Low end shelf at 100Hz

    Lo filter is present in all models, and attenuates to -3dB at 100Hz, with a slope of 12dB per octave when selected.
    EQ cut bypasses the EQ option when selected.

  • Pan - RV6 is a 10k linear pot bridging the inputs of the left and right pan amps (IC3) to ground.

    The pan amps' gain can be preset via RV2 and RV3 (located near P2 on the PCB), although these are unlikely to require much adjustment.


  • Aux outputs


  • Ducking controls


  • PFL