Sonifex RB-MM1 User Manual

AUDIO INTERFACES

Redbox - General Interfaces

RB-MM1 Mix-Minus Generator

61 Station Road, Irthlingborogh, Northants, NN9 5QE, United Kingdom Tel: [phone] Fax: [phone] Email: [e-mail] Internet: www.sonifex.co.uk

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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.

The RB-MM1 is a unit for generating a
suitable mix to send to a telephone
hybrid or codec. 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 full­band ISDN codecs, the band pass filter can
be switched out. For stereo codecs, or
conference calls, multiple RB-MM1 units
can be used.

“

A unit for generating a suitable
mix to send to a telephone hybrid
or codec.

”

Audio Specification For RB-MM1

Maximum
Input Level: +28dBu

Input
Impedance: >20kΩ

Maximum
Output Level: +28dBu

Output
Impedance: <50Ω

Output Gain Adjustable -15dB to +12dB, ref 0dBu
Range: gain via a multi-turn pot

Common
Mode Rejection: >60dB

Band Pass
Filter Range: 200Hz to 4kHz, 12dB/octave

LF Null
Adjustment: Better than 40dB at 100Hz

Mix-Minus Null: Better than 40dB at 1kHz

Frequency
Response: 20Hz - 22kHz ± 0.1dB

Distortion: 0.01% THD @ 1kHz, ref +8dBu output

(C-Message weighted)

Noise: -90dBu unity gain +6dBu

Connections

Analogue 2 x XLR 3 pin female
Inputs From (balanced) (L & R)
Mixer Output:

Analogue 1 x XLR 3 pin female (balanced) (L & R)
Input From
Telephone Fader:

Analogue
Output To TBU: 1 x XLR 3 pin male (balanced) (L & R)

Mains Input: Filtered IEC, switchable 110-120V,

or 220-240V, fused, 6W max.

Equipment Type

RB-MM1: Mix-minus generator

Physical Specification

Weight: Nett: 1.1kg Gross: 1.5kg

Dimensions
(Raw): 28cm (W) x 10.8cm (D) x 4.3cm (H)
(Boxed): 36cm (W) x 20.5cm (D) x 6cm (H)