Sonifex RB-MM1 Mix-Minus Generator

Sonifex RB-MM1 Mix-Minus Generator

Mix-minus feeds are necessary if programming comes from outside the studio or when viewers or listeners use telephone hybrids or codecs to call in. Due to the very unsettling experience of the caller, or remote talent, hearing their voice in delay, most telephone connections have delays that make off-air monitoring impossible. Refeeding the caller a mix without their voice is the solution. The RB-MM1 can be utilized in mixing desks that lack a dedicated telco channel for producing a clean feed, or mix minus.

A machine called the RB-MM1 is used to create an appropriate mix that is sent to a phone hybrid or codec. A mixer's stereo output is obtained along with a post-fader output derived from the mixer's mono telephone fader. For the caller audio to be transferred to the phone line via the hybrid, it is taken out of the station output. Neutrik XLR connectors are used for both analog audio inputs and outputs. A pre-set potentiometer on the back panel can be used to change the output level to the TBU. To regulate the cancellation null—that is, the portion of the telephone channel deducted from the mixer output signal—two multi-turn potentiometers are included: one for the full-band null and one for the LF null. To further condition the signal for the telephone hybrid, a back panel button allows you to turn on and off a band pass filter. It is possible to utilize the RB-MM1 unit with full-band ISDN codecs by swapping out the band pass filter. Several RB-MM1 units can be utilized for conference calls or stereo codecs.