Belt Pack Headphone Amplifier with Limiter & Loudspeaker.
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. A low-battery warning LED flashes when the 9V battery has depleted to 6V, giving ‘plenty of notice to swap the battery’. There are holes provide for lanyards or fixings and a belt-clip on the rear. Block diagrams are printed, helpfully, on the rear.
CM-BHA – Two-wire – Limiter and loudspeaker
The CM-BHA is for use in ‘live applications such as in-the-field news reports’. It has a ‘wide signal range capability’, applying gain of up to +20dB to the incoming signal. The volume control ‘simultaneously modifies the output volume and the input gain’, allowing input signals in excess of +24dBu to be ‘reproduced without distortion’. There is an adjustable limiter to ‘protect the listener from excessive levels’, indicated by a blue LED.
The limiter is only enabled when an earpiece or headphones are used, and when it is activated by a toggle switch on the side of the case. It is disabled when no jack is inserted, 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.
Input: +28dBu maximum, 200k ohms, electronically balanced. Input limiter threshold: -14dBu to 0dBu, adjustable, Input gain/volume: -70dB to +20dB, adjustable. Response: 20Hz to 20kHz, +/-0.5, 0dBu, 1kHz. Noise: -75dBu, A-weighted, at 0dB gain. Distortion: 0.015%, with +8dBu input, 0dB gain,10k ohms load. Output: +16dBu / +12dBu maximum, with 9V / 6V battery voltage, 1% THD, 2k ohms load. Minimum headphone impedance: 32 ohms. Maximum speaker level: +12dBu / +6dBu, 9V / 6V battery voltage, 1% THD. Dimensions: 125 (W) x 67 (D) x 48 (w x d x h)mm. Weight: 0.3kg.
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