cumbria designs





Minifilter 2


A DSP Audio Module with adjustable bandpass filtering, Auto-notch, variable Denoiser, Binaural output and dual 1W AF Power Amplifiers


The Minifilter 2 kit assembles into a compact versatile audio processor with many applications. It can be used as a stand alone unit, built into a loudpseaker enclosure tomake an amplifier DSP speaker unit or embedded in exisitng equipment as an enhancement. Its compact size and simple control interface make it a flexible solution to many audio filtering problems. This latest version includes a new control interface using two rotary encoders, a signal LED and many new features such as binaural audio, Morse announcements and an adjustable denoiser.

Minifilter Kit

The Minifilter is supplied as a kit and comprises of a single PCB populated with standard through hole parts and 4 SMD SOIC format ICs. Thanks to a high quality double sided PCB with solder mask, the kit is easily assembled by anyone experienced in soldering and able to follow written instructions.

A unique feature of the Minifilter 2 is that it can store up to 5 entire operating configurations. These comprise of filter settings, denoiser level, autonotch, binaural and volume level. By setting and saving your preferred configuration you can recall it easily or make it the power on default.

Control of the Minifilter 2 is by two rotary encoders (included) and an intuitive Morse menu system. A dual colour LED provides a visible indication of input signal level allowing the input gain to be set for optimum. An AC coupled, reduced level stereo output may be used to drive low impedance (<40 Ohms) headphones. The BTL loudspeaker outputs are suitable for driving 4 to 8 Ohm speakers. For mono applications simply leave one speaker output disconnected and adjust the balance accordingly.

The Minifilter 2 may be used as a stand alone unit or built into exisitng equipment as an upgrade. Where space is at a premium, simply omit the headers and wire direct to the pads to reduce vertical height.

With an operating voltage of +5v to +12v finding a supply source within exisitng equipment is not difficult. In cases where only higher voltages are available simple use a suitable regulator (e.g. 7808) to provide a suitable supply for the Minifilter 2.


  • Adjustable band pass filter, upper and lower skirts moveable in 50Hz steps
  • Morse menu system
  • Effective LMS Auto-notch
  • LMS Denoiser with 10 levels of denoising
  • Binaural output with spatial adjustment
  • Dual colour Signal LED
  • 5 operating configurations may be stored and recalled
  • Dual rotary encoders (included) to control all functions
  • Dual 1W BTL AF power Amplifiers
  • Digital volume control (1dB steps over 40dB range)
  • Use in mono or dual output modes
  • Headphone output
  • Install inside exisitng equipment or use as a stand alone unit
  • Operating voltage +5V to +12V,  for higher supply voltages use with a voltage regulator, e.g. 7808
  • Rotary encoders, LED, header shells and pins included


  • Size L61mm, W49mm,  H15mm
  • Supply +5v to +12v
  • 110mA typical current, dual speakers, room volume
  • High quality double sided silk screened PCB

Price 52.00 Inclusive of VAT at 20%

(Outside of the EC? Ex VAT price 43.33)