Eurorack Dual Filter using the public CEM3320/AS3320 chip.
Table of Contents
This eurorack-modul is designed for modular-synthesizers as substractive filter.
The dual-filter is build around two IC's: AS3320, a clone of that old CEM3320.
All parts are common available and DIY-friendly designed, most parts are SMD's.
- Modul Frontpanel
- Modul Backside
There are eleven 3.5mm jacks available for patching audio- and CV-signals. This descriptions are valid for part (1) {left side} and part (2) {right side} of the dual-filter.
| Jack-Name | Function | Comment | Detail |
|---|---|---|---|
| IN (1) | audio-input 1 | Level adjustable between 0 ... 2 | |
| IN (2) | audio-input 2 | Level adjustable between 0 ... 2 | Switchable input. Parallel with IN (1) or serial from OUT (1) 1||2 or 1 > 2 |
| ResCV (1) | CV-input 1 for resonance control | Level adjustable between 0 ... 10 positiv and negative voltages are supported |
|
| ResCV (2) | CV-input 2 for resonance control | Level adjustable between 0 ... 10 positiv and negative voltages are supported |
ResCV Input 2 is normalised to ResCV (1) |
| Mod. (1) | CV-input 1 for modulation control | Level adjustable between: - 0 + |
|
| Mod. (2) | CV-input 2 for modulation control | Level adjustable between: - 0 + |
Mod. Input 2 is normalised to Mod. (1) |
| OUT (1) | audio-output 1 for HP/LP/BP mode (12dB/octave) |
audio-output 1 attached to switch (1) HP := High pass mode LP := Low pass mode BP := Band pass mode |
OUT (1) is normalised to OUT (2) |
| OUT (2) | audio-output 2 for HP/LP/BP mode (12dB/octave) |
audio-output 2 attached to switch (2) HP := High pass mode LP := Low pass mode BP := Band pass mode |
summed OUT (2) and OUT (1), if no patch-cabel is plugged into OUT (1) |
| LP24 (1) | audio-output 1 for LP mode only (24dB/octave) |
Low pass only audio-output with 24dB/octave (simultaneously usable with 'OUT (1)') |
LP24 (1) is normalised to LP24 (2) |
| LP24 (2) | audio-output 2 for LP mode only (24dB/octave) |
Low pass only audio-output with 24dB/octave (simultaneously usable with 'OUT (2)') |
summed LP24 (2) and LP24 (1), if no patch-cabel is plugged into LP24 (1) |
| 1V/Oct. | CV-input for 1Voltage/Octave frequency-control | Both filter-parts (1 and 2) are controlled with this voltage | The Track-poti can reduce the CV-input voltage This CV-input is normalised to Eurorack-Bus pitch-CV if no patch-cable is plugged into the jack |
There are eleven potentiometers with following functions:
| Poti-Name | Function | Comment | Detail |
|---|---|---|---|
| Frequency (1) | Cut-Off frequency 20Hz to 20kHz | Filter cutoff frequency 1 for part 1 (left filter) range: min := < 20 Hz max := > 20kHz 12 o'clock position := 440Hz |
|
| Frequency (2) | Cut-Off frequency 20Hz to 20kHz | Filter cutoff frequency 2 for part 2 (right filter) range: min := < 20 Hz max := > 20kHz 12 o'clock position := 440Hz |
Switchable to slave-mode locked to Frequency (1) FSync := Slavemode On, else Off |
| Track | Keyboard-CV tracking potentiom. | Keyboard-CV tracking adjustable 0 := None 1 := 1V/octave |
This CV-voltage is assigned to both parts of the dual-filter |
| Res. (1) | Resonance potentiometer 1 | Resonance adjustment for part 1 (left filter) 0 := None 10 := maximum, self oscillation 12 o'clock position := starting oscillation |
|
| Res. (2) | Resonance potentiometer 2 | Resonance adjustment for part 2 (right filter) 0 := None 10 := maximum, self oscillation 12 o'clock position := starting oscillation |
|
| IN (1) | Audio input-level attenuator 1 | Level adjustable between 0 ... 2 for part 1 (left filter) 0 := No audio signal from IN-jack 1 := IN-level amplified 0dB 2 := IN-level amplified 6dB |
|
| IN (2) | Audio input-level attenuator 2 | Level adjustable between 0 ... 2 for part 2 (right filter) 0 := No audio signal from IN-jack 1 := IN-level amplified 0dB 2 := IN-level amplified 6dB |
|
| ResCV (1) | Resonance-CV attenuator 1 | Resonance-CV attenuator for part 1 (left filter) 0 := None 10 := maximum |
|
| ResCV (2) | Resonance-CV attenuator 2 | Resonance-CV attenuator for part 2 (right filter) 0 := None 10 := maximum |
|
| Mod. (1) | Modulation-CV attenuverter 1 | Modulation-CV attenuverter 1 for part 1 (left filter) controlling the amount and polarity of modulation - := negative modulation + := positive modulation 0 := no modulation |
|
| Mod. (2) | Modulation-CV attenuverter 2 | Modulation-CV attenuverter 2 for part 2 (right filter) controlling the amount and polarity of modulation - := negative modulation + := positive modulation 0 := no modulation |
There are four switches to control the behaviour of signals.
| Switch | Function | Comment |
|---|---|---|
| HP/LP/BP (1) | switch (1) attached to OUT (1) HP := High pass mode LP := Low pass mode BP := Band pass mode |
|
| HP/LP/BP (2) | switch (2) attached to OUT (2) HP := High pass mode LP := Low pass mode BP := Band pass mode |
|
| 1||2 or 1>2 | switch is controlling the input-signal on IN (2) 1||2 := parallel mode: IN (2) get the signal from IN (1) 1>2 := serial mode: IN (2) get the signal from OUT (1) left filter OUTput |
Only available in normalised mode (no patch-cable on IN (2)). |
| FSync or Off | switch to control the frequency-cutoff on the right filter FSync := Slave-mode on the right filter (2). The left frequency-cutoff (1) is the master-control and the right frequency-cutoff (2) controls the offset on the right filter Off := Normal-mode for frequency-cutoff (2) on the right filter |
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size:
width: 16HP
depth: 45mm -
power:
5Volt, 0 mA
+12Volt, 50mA
-12Volt, 50mA -
frequency range: 20Hz to 20kHz.
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frequency CV scale: 1V/Oct, adjustable with poti: 'Track'.
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cutoff-frequency 2 (right filter) switchable to slave-mode to be controlled by cutoff-frequency 1.
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signal input, AC-coupled signal path, level adjustable with potis: 'IN(1)' & 'IN(2)'.
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signal input 2 (right filter) switchable to modes: 'parallel' input 1 or 'serial' OUTput1.
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modulation inputs, DC-coupled signal path, amount adjustable with potis: 'Mod.(1)' & 'Mod.(2)'.
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resonance inputs, DC-coupled signal path, amount adjustable with potis: 'ResCV(1)' & 'ResCV(2)'.
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signal input impedance: > 50kOhm.
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signal output impedance: 470 Ohm.
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CV-Input impedance: 100kOhm.
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expandable with second '2MoreF'filter to get four filters in parallel.
Hardware:cc by-nc-sa 4.0 (details)