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Sonifex RB-MM1

Mix Minus Generator

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For outdoor program feeds or calls via a hybrid or codec, mix-minus feeds are required.

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RB-MM1 $422.00
  • The RB-MM1 is a unit for generating a suitable mix to send to a telephone hybrid or codec.

    Whenever programming originates from outside of the studio, or if listeners/viewers are calling up a phone-in using telephone hybrids or codecs, mix-minus feeds are required. Most telephone lines incur delays which prohibit off-air monitoring, because the caller, or remote talent, would hear their own voice in delay which is very disconcerting. The solution is to feed a mix back to the caller minus his or her own voice. Some mixing desks do not have a dedicated telco channel to generate a clean-feed, or mix minus, so the RB-MM1 can be used.

    A stereo output is taken from a mixer, together with a post fader output from the mono telephone fader on the mixer. The caller audio is removed from the station output so that it can be sent to the telephone line via the hybrid.

    Analogue audio inputs and outputs are via Neutrik XLR connectors. The output level to the TBU can be adjusted using a rear panel pre-set potentiometer. To control the cancellation null, 2 multi-turn potentiometers are provided, one for the LF null and the other for the full-band null. Additionally, a band pass filter can be switched in and out, via a rear panel switch, to condition the signal for the telephone hybrid.

    To use the RB-MM1 unit with full-band ISDN codecs, the band pass filter can be switched out. For stereo codecs, or conference calls, multiple RB-MM1 units can be used.

  • Specifications
      Audio Specification
    Maximum Input Level +28dBu
    Input Impedance >20kohms
    Maximum Output Level   +28dBu
    Output Impedance   <50ohms
    Output Gain Range   Adjustable -15dB to +12dB, ref 0dBu gain via multi-turn pot
    Common Mode Rejection   >60dB
    Band Pass Filter Range   200Hz to 4kHz, 12dB/octave
    LF Null Adjustment   Better than 40dB at 100kHz
    Mix-Minus Null   Better than 40dB at 1kHz
    Frequency Response   20Hz - 22kHz +/-0.1dB  
    Noise (RMS)   <-90dB unity gain, ref +6dBu output
    Distortion   0.01% THD @ 1kHz, ref +8dBu output (C-Message weighted)
    Analogue Inputs from Mixer Output   2 x XLR 3 pin female (balanced)(L and R)
    Analogue Input from Telephone Fader   1 x XLR 3 pin female (balanced)(L and R)
    Analogue Output to TBU   1 x XLR 3 pin male (balanced)(L and R)
    Mains Input   Filtered IEC, switchable 110-120V or 220-240V, fused, 6W max
      Physical Specification
    Weight Nett: 1.0kg Gross: 1.45kg
    Dimensions Raw: 28cm (W) x 10.8cm (D) x 4.2cm (H) (1U) Boxed: 36cm (W) x 20.5cm (D) x 6cm (H)
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