AMSynths AM8044 Cascade VCF User manual

AMSynths
AM8044 Cascade VCF & VCA
User Manual
24dB/Octave Low Pass Filter
& Linear Voltage Controlled Amplifier
© AMSynths 2013
Rob Keeble, Owner & Designer
Contact: [e-mail]
Web Site: www.amsynths.co.uk

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Contents
1. Welcome
2. Front Panel
3. Connections & Controls
4. Module Description
5. Configuration
6. Warranty & Support
7. Specifications

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1Welcome
Thank you for purchasing an AMSynths product.
The AM8044 analog filter and amplifier module has been
designed and hand built in the UK to exacting quality
standards. The module uses high quality electronic
components and particular attention has been paid to the
quality of the audio signal path, stability of the control
circuits and the long term life of the product.
This user manual explains the basic functions of the
module, as well the historic background to its development,
how to install the module and the warranty and support.
AMSynths modules are produced in low volumes, with each
module having a unique holographic serial number and a
certificate of ownership. You own a rare and beautiful
analog synthesizer module that will provide many years of
amazing sounds and musical inspiration.
Rob Keeble
Owner & Designer
AMSynths
April 2013

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2Front Panel
AUDIO INPUTS:
InA, InB
CONTROL INPUTS:
CV1, CV2, Env
AUDIO OUTPUTS:
Out
CONTROL POTS:
Signal A (white)
Signal B (white)
Frequency (blue)
Resonance (red)
Key Track (blue)
CV1 (blue)
CV2 (blue)
Gain/Env (yellow)
The serial number is on a small silver holographic sticker
on the inside of the front panel.

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3Module Description
This module is designed around the SSM2044 VCF chip that
appeared in a variety of analog synthesizers in the early
1980’s, including the Korg Poly 6 and PPG Wave 2.2. The
SSM2044 IC was designed by Dave Rossum and Ron Dow
in 1980 as a 24dB low pass filter circuit that emulates the
Moog ladder filter but with improved accuracy and lower
noise, using current mirrors. The design is unique and is
called a Cascade filter.
We have added a VCA after the VCF output, so you can
connect up a dual envelope generator and make
Astounding Sounds!
Audio signals are buffered before and after the SSM2044 by
high quality Op Amps. The VCA is built from the high quality
BA6110 OTA chip, with added diode protection against any
negative voltages. The response is linear, making it ideal for
connecting to exponential ADSR’s.
The SSM2044 was produced in large numbers in the mid
1980’s and there are still many hundreds of NOS chips in
the market, over 30 years after it was invented.
We love the sound of this filter. which we have carefully
crafted into a new EuroRack module using modern
components, we hope you like it as well!

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4Connections & Controls
The two uppermost jack sockets INA and INB are for
connecting audio signals into the input side of the filter,
these signals are mixed together. The level of each audio
signal can be varied from nil to maximum using the front
panel rotary potentiometers Signal A and Signal B.
The next jack socket Env is for connecting a modulation
control voltage to modify the volume of the module.
The middle jack sockets CV1 and CV2 are for connecting
modulation control voltages into the filter. These signals
vary the cut off frequency of the filter, with the front panel
rotary potentiometers adjusting the amount of modulation.
The lowest jack socket marked Out is the audio signal
output of the filter and it is typically connected to a VCA.
The Frequency potentiometer varies the cut off frequency
of the filter. At the minimum setting the filter will cut off all
frequencies with no audio output and at the maximum
setting the filter will pass all frequencies.
The Key Track potentiometer adjusts the amount by which
the keyboard note value control voltage on the internal
Doepfer bus controls frequency cut-off. This enables
brighter sounds as higher notes are played.
The Resonance potentiometer adjusts the resonant peak of
the filter from a minimum setting of no resonance, through
subtle resonance enhancement to a maximum setting when
the filter will break into self oscillation.
The Gain/Env potentiometer adjusts either the VCA gain or
when a jack is inserted into Env socket, it controls the
amount the CV signal varies the level of the VCA.

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5Configuration
The AM8044 module occupies 14HP of EuroRack space and
is fully compatible with various Euro Rack cases, especially
Doepfer. The height of the panel is 128.5 mm and there
are four mounting holes at each corner of the module.
Four 3mm diameter mounting screws and washers are
included with the AM8044 to enable you to securely mount
the module into your rack.
The module should be connected to the 12V Doepfer style
power bus within your case using the included AMSynths
multi-way power cable. Ensure the power is OFF before
connecting the module and BE VERY CAREFUL to ensure
that the power connector to the bus is connected with the
red stripe of the cable lined up with -12V (negative 12V).
This is standard Euro Rack power connection but be VERY
CAREFUL to get this right! Damaged modules will not be
replaced under warranty when the power has been
misconnected. The power socket on the AMSynths module
is keyed so that the cable can only be inserted the correct
way.

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6Warranty & Support
Repairs resulting from a defect of the module or its
construction process are covered by a one year warranty,
with the customer paying transit costs to AMSynths in the
UK.
Damage to the module resulting from incorrect power
supply voltages, backwards power cable connection,
abusive usage, fluid encroachment or out-of specification
voltage input are not covered by the warranty and normal
service rates apply.
AMSynths implies and accepts no responsibility for
undesirable harm to a person or apparatus caused through
operation of this device.
If you have questions regarding the use of this module or
you need technical support please contact AMSynths via
email at [e-mail].

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7Specifications
Power Supply:
+12V, GND and -12V standard Doepfer 10 pin connector
RED stripe on power cable is -12V (NEGATIVE 12V)
Current consumption:
21mA both rails
Dimensions:
128.5mm (Height) x 70.8 mm (Width)
Euro Rack Size:
14HP/TE
Panel:
2mm machined aluminum with colour photographic print.
Frequency
20 Hz to 20 kHz
Resonance
0 to self oscillation
VCA Control Voltage
0 to +10V (minimum to maximum gain)
Output Impedance:
1k ohm
Input Impedance:
100k ohm