ADT Big Blue Mixer VCA Box (BOTTOM 3U)

Cstom Mixer / VCA Control Module

16 stereo input modules and master module
19" x 4U, depth - without knobs on the faceplate and mating connectors, 245 mm = 9.65"

Channel Inputs:

• stereo, unbalanced, on 3.5 mm jacks on the faceplate
• Input impedance > 100 kohms
• max. input level > + 24 dBu = 34 Vss

Channel Direct Outputs:

• stereo, electronically balanced, on 25-pin d-subs on the rear panel of the VCA-box
• post fader - pre CUT
• source impedance < 50 ohms
• min. load resistance >1200 ohms for full headroom
• max. output level + 30 dBu

Input Module
Input Mode:

• 4-position stepper switch for
• standard stereo (ST),
• mono (M) - left and right input are mixed and the mono signal feeds the internal stereo channels in parallel
• left only (L) - only the left input signal feeds both internal stereo channels in parallel
• right only (R) - only the right input signal feeds both internal stereo channels in parallel

Input Gain:

• +/- 20 dB range, calibrated center detent at 0 dB
• range internally adjustable up to ~ 34 dB
• independent adjustment for gain and attenuation

Pan-Pot:

• stereo pan-pot with center click and 0 dB center attenuation
• The output of the pan-pot feeds the stereo mix bus

3-color peak present leds

• separate for left and right, indicates the level post input gain
• 20 dB - green, 0 dB - yellow,
• red indicates that the remaining headroom is 4 dB or less

Aux-Send:

• Stereo aux-send, default post fader, pre cut, pre pan-pot switched to pre fader by central switch in the master module

CV input:

• unbalanced, on 3.5 mm jack on the faceplate
• input impedance > 200 kohms
• input voltage range from DC to 20 kHz, +/- 20 volts negative input voltages are clamped below - 5 volts
• Mode switch with 3-position stepper switch LIN / OFF / LOG:
• default law with ATT/GAIN pot and OFF(set) pot in center position (subject to be modified after testing the sample module):
  • CV / lin gain (as factor) / log gain (in dB)
  • below -5v / off / off
  • -5v / off / off
  • -4v / 0.2 / -80 dB
  • -3v / 0.4 / -60 dB
  • -2v / 0.6 / -40 dB
  • -1v / 0.8 / -20 dB
  • 0v / 1.0 / 0 dB -> No change, equal to CV input OFF or ATT pot all to the left
  • +1v / 1.2 / +4 dB
  • +2v / 1.4 / +8 dB
  • +3v / 1.6 / +12 dB
  • +4v / 1.8 / +16 dB
  • +5v / 2.0 / +20 dB
  • +6v / 2.2 / +24 dB
  • +7v / 2.4 / +28 dB
  • +8v / 2.6 / +32 dB
  • +9v / 2.8 / +36 dB
  • +10v / 3.0 / +40 dB
• Attenuation / Gain pot with calibrated center click at 0 dB / input voltage not changes, control range from 'OFF' to gain of 2 (gain range internally adjusted by trimpots from 'attenuation only' to 'gain > 3')
• Offset pot with calibrated center click at 0 offset, default range +/- 5 volts, internally adjusted by trimpot (range can be extended up to +/- 10 volts or reduced), the offset is added to the cv input post attenuation/gain pot

Master Module
Stereo master:

• Stereo master chain with bus amp
• balanced insert send and return post bus amp, pre VCA, outputs on xlr male, inputs on xlr female, located on the rear panel of the vcabox
• Insert switch
• AFL to Master switch
• stereo vca master fader and electronically balanced stereo master outputs on xlr male located on the rear panel of the vcabox
• overall gain from channel input to insert output and master output with master fader at 0 dB, input gain and channel fader at 0 dB and pan-pot at center: 6 dB

Aux Master:

• Stereo aux master with rotary master fader, Aux-Cut switch and central PRE switch
• max. gain, referred to channel input with channel fader and input gain at 0 dB, Aux faders in the channel and aux master all to the right: 6 dB
• electronically balanced stereo aux master outputs on xlr male located on the rear panel of the vcabox

AFL-Master:

• Stereo AFL master with calibrated direct outputs on XLR male located on the rear panel of the vcabox
• if AFL TO MST is pressed, the AFL master is switched to the input of the master fader post master insert, if one or more AFL switches are pressed.
• all Outputs are electronically balanced,
  output source resistance < 50 ohms
  min. load resistance for max. headroom, > 1200 ohms
  max. output level, + 30 dBu

Meter:

• stereo LED-Meter with 15 leds per channel, range +15 to -30 dB with 2.5 dB steps, reads stereo master output

Overall specs

• Frequency response: 10 Hz to 50 kHz +/- 0.25 dB ; 100 kHz < - 1 dB
• Phase response: 20 Hz to 20 kHz + 10 / - 30 ∞
• Power bandwidth @ + 30 dBu output level 20 Hz to 50 kHz
• Dynamic range, referred to +30 dBu: Channel input to channel output, input gain & fader at 0 dB, at least 120 dB; Master or Aux outputs, all faders down, master at 0 dB, at least 114 dB; all channels faders and input gain pots @ 0 dB, all inputs shorted, at least 110 dB
• Power supply: external power supply unit 19" x 3U x 9.5"
  115 volts / 60 Hz, 500 watts max; Euro power inlet
  connected to the vca-box by 20 ft. cable.