ALM MUM M8 User manual

ALM-018 - ‘MUM M8’
ALM-018
‘MUM M8’
- Operation Manual -
(V0.1)

Introduction 3............................................................................................
Technical Specifications 4
Core Operation 5.......................................................................................
Panel Layout 5
General Usage 6
Calibration 7...............................................................................................
Limited Warranty 8.....................................................................................
Support 9...................................................................................................
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ALM-018 - ‘MUM M8’
Introduction
‘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.
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ALM-018 - ‘MUM M8’
Technical Specifications
•Supply: +/-12V
•Current Draw: +12v 40ma / -12v 40ma
•Size: 8 HP
•Depth: 32mm (including power header)
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ALM-018 - ‘MUM M8’
Core Operation
Panel Layout
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Freq
Freq
+
-
In
In
VCA
Res Out
Clip Cut off
Resonance
MUM M8
Frequency cut off offset control
Resonance offset control.
Resonance CV offset attention
Filter output
2nd CV input for cut off control
(No attenuation)
Clipping indication
VCA level & attneutaion control
VCA CV input
Audio Input with VCA
Audio input
Attenuverter for lower
main CV input cut off control

ALM-018 - ‘MUM M8’
General Usage
An audio signal is patched into either ‘In’ input. The upper input is controlled by a
VCA which can amplify signals into the the filter core. (and thus aid clipped distortion/
saturation to occur). With nothing patched into the VCA input, the thumb control will
control the audio input level - when patched in it acts as at attenuation control. The
audio signals will then be mixed and pass through the filter core output on the ‘Out’
jack on the bottom right of the module.
The filter core has both a controllable cut off frequency and resonance. The cut off
frequency offset can be controlled manually via the large white knob and by means of
voltage control through the the two ‘freq’ inputs. The bottom ‘freq' input has an
attenuversion control allowing both attenuation and inversion of the control signal. All
CV inputs and knob offset are combined together to set the final filter frequency cut
off. Resonance is controlled manually via the smaller knob control and via the ‘Res’
input and associated attenuator. The resonance can get particularly aggressive going
into self oscillation with the control past 12 o’clock.
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ALM-018 - ‘MUM M8’
Calibration
There are two trimmers on the rear on the module which can be used to adjust the
minimum cut off frequency for the filter. Because of the filters architecture, too low a
cut off frequency will introduce high pitched noise into the audio signal (from the
filters controlling clock signal).
The top trimmer (marked ‘FREQ OFF ADJ’ ) sets the ‘base’ cut off frequency - i.e the
cut off will effect the main control knob on front of module turned full counter
clockwise and no CV inputs patched. The lower trimmer (marked ‘FREQ MIN ADJ’) hard
limits the minimum frequency of the filter (from knob or cv input). The trimmers are
adjusted with a small flat head screwdriver.
To calibrate;
1. Turn filter knob full counter clock wise (CCW), Resonance knob full CW - so filter
is in self oscillation.
2. Turn top ‘FREQ OFF ADJ’ trimmer full CCW. Turn lower ‘FREQ MIN ADJ’ trimmer
full CW. You should now hear no resonance but the clock noise.
3. Turn ‘FREQ OFF ADJ’ CW until you can hear just resonance and so that the clock
noise has subsided (approx 1/4 to 1/3 of a turn)
4. Turn ‘FREQ MIN ADJ’ CCW to just before the point it affects the resonance
frequency.
Note the module is pre calibrated at the factory but by all means adjust to taste!!
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ALM-018 - ‘MUM M8’
Limited Warranty
From the date of manufacture this device is guaranteed for a period of 2 years
against any manufacturing or material defects. Any such defects will be repaired or
replaced at the discretion of ALM. This does not apply to;
•Physical damage arising for mistreating (i,e dropping, submerging etc).
•Damage caused by incorrect power connections.
•Overexposure to heat or direct sunlight.
•Damage caused by inappropriate or misuse.
•Use of incorrect or non official firmware
No responsibility is implied or accepted for harm to person or apparatus caused
through operation of this product.
By using this product you agree to these terms.
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ALM-018 - ‘MUM M8’
Support
For the latest news, additional info, downloads and firmware updates please visit
the ALM website at http://busycircuits.com and follow @busycircuits on twitter.
Please send any questions or comments to [e-mail]
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