UK Sales: 0191 418 1122         International: +44 191 418 1133


14 July 2024
  • Next day delivery
  • Free standard UK delivery
    on all orders over £100
  • Industry leading
    customer service
  • Free technical support
    from our team of experts


3 items

These are portable, battery powered units for use in a variety of broadcast applications including location reporting as well as both location and studio cueing and talkback systems. All units use low-power circuitry for headphone amplifiers, and in the case of the four-wire and IFB models microphone amplifiers suitable for dynamic microphones. Both a headphone amplifier, with a loudspeaker muted by the headphone jack, and headset communication units are offered.

The belt-packs have line level connectors on the lower surface, with headphone/headset connections on the upper surface, together with controls. A battery holder on one side has a drawer for a single PP9 battery. There are holes provide for lanyards or fixings and a belt-clip on the rear. Block diagrams are printed, helpfully, on the rear.


Sonifex CM-BHA is for use in 'live applications such as in-the-field news reports', and provides audio monitoring via built-in speaker or headphones. It has a 'wide signal range capability', applying gain of up to +30dB to the incoming signal. The volume control 'simultaneously modifies the output volume and the input gain', allowing input signals in excess of +18dBu to be 'reproduced without distortion'. Line input is by way of balanced 3-pin XLR connector, and loop through output - for use with daisy-chaining; is also by way of 3-pin XLR connection.

An inbuilt limiter can be enabled to prevent high outputs damaging the user's ears. The limiter is activated manually by way of a toggle switch on the side of the case, and operation is identified via a blue LED. It is disabled when only the inbuilt speaker is active, allowing a higher volume to be passed to the speaker for 'squawk mode' use. The low power circuitry gives up to 200 hours use from a single alkaline 9V PP3 battery, and a 3mm red LED indicates low battery warning when the inserted battery cell falls below 6V.

Line input impedance: 200k ohms, balanced. Input limiter threshold: -6dBu to +6dBu, adjustable. Maximum input level: +18dBu. Input gain: -60dB to +30dB, adjustable. Frequency response: +/-0.5dB, reference 0dBu 1kHz. Distortion: Less than 0.015%, reference +8dBu input, 0dB gain, 10k ohm load. Maximum headphone output level: +16dBu, 9V battery voltage; +12dBu, 6V battery voltage. Minimum headphone impedance: 32ohms. Maximum speaker level: +12dBu, 9V battery; +6dBu, 6V battery. Dimensions (WxDxH): 12.5 x 6.7 x 4.8cm. Weight: 0.3kg.

CM-BH4W - Four-wire, 6.35mm jack headset socket

A 'four-wire' communication unit for use 'in a multitude of TV and radio broadcasting applications', including talkback/cue, IFB and commentary, the CM-BH4W uses audio transformers at its input and output, providing galvanic isolation from outside interference, ensuring communications are 'loud and clear, every time'. It has a 3-pole, 6.35mm jack socket for connecting a headset and female and male, 3-pin, XLR connectors for line-level input and output, respectively. There is a rotary, combined, on/off and volume control and a press-to-talk button. A switch on the side selects IFB or four-wire mode.

In four-wire mode, the unit acts as a two-way intercom, with input audio routed to the headset earpiece, and microphone audio is routed to the output upon pressing the talk button. The output level is maintained at +2dBu peak level by a built-in AGC. In IFB mode, the input audio is routed to the output, and is interrupted by the microphone signal when the talk switch is pressed. The talk switch can easily be converted from momentary to latching operation to suit your application.

CM-BH4W automatically switches off when the headset jack is removed, and single alkaline 9V PP3 battery gives up to 150 hours use.

Microphone input: 1.5k ohms, unbalanced for 200ohm dynamic microphone. Limiter input threshold: -60dBu. Line output level: +2dBu. Line output impedance: 150ohms, transformer balanced. Line input: +24dBu, maximum, 10k ohms, transformer balanced. Input gain/volume: Off to +10dB, adjustable. Headphone output: +7dBu maximum, 9V battery voltage, 1% THD, 100 ohm load. Headphones: 100 ohms minimum impedance. Dimensions (WxDxH): 12.5 x 6.7 x 4.8cm. Weight: 0.3kg.

CM-BH4WX - Four-wire, 4-pin XLR headset socket

Sonifex CM-BH4WX is a version of CM-BH4W with a 4-pin, male XLR, balanced headset connection instead of a stereo jack connector. In all other respects it is the same as the CM-BH4W.

  Description Price £
ex. VAT
Add to basket
SONIFEX CM-BHA BELT PACK Headphone amplifier with loudspeaker, loop thru output Stock code: 95-7667
Ordered on demand, available in 4‑6 weeks. Need it sooner? Call us
SONIFEX CM-BH4W BELT PACK Talkback, IFB, commentary, 4-wire headset amplifier, 6.35mm jack Stock code: 95-7668
Ordered on demand, cancellations may incur charges, available in 4‑6 weeks. Need it sooner? Call us
SONIFEX CM-BH4WX BELT PACK Talkback, IFB, commentary, 4-wire headset amplifier, XLR4 headset socket Stock code: 95-7669
Ordered on demand, cancellations may incur charges, available in 3‑5 working days. Need it sooner? Call us