ALM Busy Circuits MUM M8

‘MUM M8’ is an 8hp Eurorack low pass filter building on the filter design used in the classic Akai S950 12 bit sampler with the addition of resonance, voltage control, clipped saturation and a dedicated VCA.

The low pass filter gives the recognisable super smooth vacuum like tone sucking sound which works magic on complex sources. The addition of clipped overdrive and intentionally aggressive self oscillating resonance compliment the smooth filter core by juxtaposing it into more wasp like territory with acidic squeals and a more gritty sound.
Mum M8 features dual voltage control with attenuation (and inversion) of filter cut off and voltage control of resonance together with dual audio inputs - one of which includes a VCA to with the capability to aid overdriving signals into the filter core.

The filter core is a 6th Order Butterworth switched capacitor type design featuring an analog core but controlled by a high speed digital clock. This produces the characteristic smooth sounding filter but, as with the original S950, has a relatively high minimum cut off as to avoid ‘clock bleed’ into the filter output from the digital control. This minimum cut of point (and introduction of bleed if required) can be controlled via trimmers on the rear of the module (see calibration chapter). It is not unusual for there still to be some low level artefacts from the clock present, particularly during filter sweeps - these add to the filters character.

The motivation for the module came from discussing filters in classic samplers with the artist Jack Adams - aka Mumdance. Jack suggested investigating the S950’s filter well known as for it use in classic use in early jungle and hardcore. From that point onward Jack provided inspiration, help and feedback in the development of the filter. Big up Mumdance.