Compact In-Line DSP Noise Cancelling Module

Remove noise and interference so you can hear clearly....for a stress-free listening experience!

The bhi Compact In-Line module is a noise cancelling in-line module suitable for anyone struggling with background noise during listening experiences. It fits directly between your radio and headphones or a powered speaker. Its intelligent microprocessor-controlled system can distinguish between speech and interference, dramatically improving audio clarity. Whether you're a radio enthusiast, a listener with hearing challenges, or someone who needs crisp audio in noisy environments, this device offers a solution.

Constructed from tough, impact-resistant black ABS plastic, the module is built for durability and portability. Its intuitive design allows users to quickly adjust noise cancellation levels in real-time using two rotary encoders with push-button functionality. With over 40 hours of battery life and the ability to work with various audio sources, the Compact In-Line DSP noise cancelling module provides an enhanced listening experience that brings clarity and comfort to your audio consumption.

Not sure which of our in-line modules to choose? Read our guide to the different in-line module options.

Who is the Compact In-Line module for?

• Amateur radio
• Shortwave listening
• Covert surveillance/listening

Simple control of all functions

The Compact In-Line functions are microprocessor-controlled by two rotary encoders with pushbuttons. The unit can be adjusted in "real time" to suit your noisy conditions. The “Power/Volume” control switches the unit on and off and adjusts the audio volume. The “Filter Level” control adjusts the filter level in "real time", enabling you to respond quickly to changes in conditions. You can also select between a single mono signal or stereo mode. The Compact In-Line is particularly useful for portable/mobile use as it can be powered by 2 x AA batteries. The unit is suitable for all radios and receivers and software-defined radios (SDR), including Elecraft and FlexRadio products.

Read the excellent article on this unit by Jock Elliott KB2GOM in the SWLing post online

Boost your audio

Why not boost your receive audio further and use one of our EQ20 10W parametric equaliser units with your Compact In-Line? Simply connect the "Phones Out" signal to the input of the EQ20 and connect your passive speaker or headphones to the EQ20 output. You will be able to fine-tune your audio to suit your own hearing. This is especially useful if you suffer from hearing loss.

Shop bundled offers

• Compact In-Line & International Power Supply Bundle
• Compact In-Line & Bypass Switch Bundle

Specification

Power Supply

• External supply: 8 to 16V (nominally 30mA, max 350mA peak)
• Reverse polarity protected
• Internal batteries: Type: AA x 2 (Alkaline or NiMH recommended)
• Reverse polarity protected
• Low battery indication threshold: 2.1V ±0.1V
• Low battery indication: LED colour changes to red.
• End-of-life threshold: <1.5V
• Life: 40 hours typical (Alkaline or 2500mAH NiMh).
• Auto power-off: 60 minutes if input signal < 60mVpk-pk
• Auto power-off can be disabled if desired.

Audio Inputs

• Speaker level in: Stereo or Mono
• Input Impedance: ~7 Ohms
• Max withstand input power: 2 Watts RMS per channel
• Max input amplitude: 3.9Vpk-pk
• Line level in: Stereo or Mono
• Impedance: 6.7k Ohms typical
• Max input amplitude: 1.6Vpk-pk
• Overload indication: LED flashes for at least 3 seconds

Audio Outputs

• Phones out: Stereo or Mono
• Impedance: > 4 Ohms (Can also be used as Line Level output).
• Max power output: 0.2 Watts RMS per channel
• Volume levels: 16 levels in 3dB steps.

DSP Noise Filtering

• Powerful High-performance audio processor
• Modes: Enabled / Disabled (DSP filter off)
• Levels: 8
• Noise suppression: 8 to 40dB
• Tone suppression: Up to 65dB
• Ultra-low latency of 38mS

Size & weight

• Size 125 x 70 x 37mm
• Unit weight 0.125Kg
• Case made from tough, impact-resistant black ABS plastic

Testimonials

"Noticeable increase in clarity in what is sadly a noisy reception area. Great job at reducing QRM" - Mark

"Unit very effective" - Bill GM8RBR

Watch this great video review of the Compact In-Line by Precision Group

FAQs

How do I power the unit?

The module supports two AA batteries (Alkaline or NiMH) with around 40 hours of operation, or use an external 8–16 V DC power supply with the supplied fused DC lead. You can also use the bhi PSU12-2A-WW 12V DC power supply along with the bhi 1.3mm to 2.1mm power adapter (ADAPTER1.3MM). Batteries are bypassed when external power is used.

Is it compatible with both mono and stereo audio sources?

Yes, it handles both mono and stereo input on speaker level or line level, and outputs to stereo headphones or mono/stereo speakers, passive speakers or powered speakers.

How many noise reduction levels does it offer?

There are eight noise cancelling levels ranging from 9 to 40 dB of noise reduction, plus tone suppression up to 65 dB.

Is there any latency from the DSP processing?

There is only very low latency, approximately 32–38 ms, ensuring minimal delay and not noticeable to the human ear.

Can you use a passive speaker or only headphones?

It’s primarily designed for headphones (≥ 4 Ω), but it can also drive a passive 4–8 Ω speaker if needed or powered speakers for more audio output.

Does it have an audio bypass when turned off?

No, there is no power off bypass switch on this unit, but with the filter off (red LED), you effectively have the raw audio signal, which bypasses the DSP filter circuit, albeit amplified. You can use the bhi Bypass Switch with the Compact In-Line to give you a power-off bypass feature for this unit. Turning the unit off with the Bypass Switch connected gives you a power-off bypass feature.

Can this unit be used with any radio or receiver?

The module is compatible with most receivers, transceivers, and SDR radios that provide a standard audio output connection.

Can I use it in both fixed and portable operations?

Yes, it’s compact and lightweight, making it ideal for shack or field operations.