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AM2110 Module - Eµ High Pass VCF
Overview This module is an exact replica of the 24dB High Pass Filter in the Eµ Systems Modular system. Dave Rossum originally designed the high pass filter with discrete components
in 1974. However 4 years later in 1978 the filter was redesigned to make use of the legendary SSM2040 chip.
It's a warm and smooth sounding high pass filter, well worth having alongside the more popular and traditional low pass
filters. The same circuit also appeared in the Eµ Audity and SSM Voice Card.
AM2100 Circuit
The filter design follows the original design, although with some minor upgrades to the Op Amps. The SSM2040 filter chip is the core of the circuit, configured in high pass mode with four 2000pF polystyrene capacitors.
The CV's
are summed by a 741 Op Amp, and a TL082 dual Op Amp to bring the signal down and then back up to normal modular signal path voltages. The AM module uses precision Op Amps, the OP177G for CV summing and the OPA134 for the audio path.
There is no requirement for temperature compensation as the filter will not oscillate. There is no feedback circuit for resonance. This is typical of most HPF's.
Front Panel
The front panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eµ Modular. There are 3 variable signal inputs to enable mixing of various audio sources, coarse and fine frequency controls, resonance and full, variable + and variable - CV controls. A 2 position centre-off toggle switch selects whether the keyboard or seqeuncer CV is brought in as a control voltage.
Build History The schematic was transferred into Eagle CAD in late 2004, and a 80mmx100mm board laided out around the same time. The prototype module was built in July 2005, and it was operational immediately with no bugs.
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 Resources
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 * AM FAQ's more »
* Hard to find Parts more »
* Eµ Modular Catalog more »
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 * AM2110 Project Notes
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 * AM2110 PCB layout
Zipped .BRD Eagle CAD
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 * AM2110 front panel
Zipped .FPD Front Panel
Designer file
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Front Panel |
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AM2110 front panel with 3 signal pots on the left, coarse and fine frequency
control, resonance and 2 CV pots. The toggle switch selects whether CV's from the MIDI converter or an external CV seqeuncer are used.
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PCB - populated |
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AM2110 PCB populated and mounted to the front panel. The PCB is designed to be
mounted vertically but the panel error meant it had to go this way round.
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