1MoreF

Eurorack filter based on CEM/AS3320 used in modular Synthesizers.

Table of Contents

• Introduction
• Construction Guide
• Calibration
• Technical data
• References
• License

Introduction

This eurorack-modul is designed for modular-synthesizers as substractive filter.
The filter is build around that IC: AS3320, a clone of that old CEM3320.
All parts are common available and DIY-friendly designed.

• Modul Frontpanel

• Modul Backside

There are five 3.5mm jacks available for patching audio- and CV-signals.

Jack-Name	Function	Comment
IN	audio-input	Level adjustable between 0 ... 2
ResCV	CV-input for resonance control	Level adjustable between 0 ... 10 (only positiv voltages are used, negativ voltages are clipped)
Mod.	CV-input for modulation control	Level adjustable between - 0 +
OUT	audio-output for HP/LP/BP mode (12dB/octave)	audio-output attached to switch HP := High pass mode LP := Low pass mode BP := Band pass mode
LP24	audio-output for LP mode only (24dB/octave)	Low pass only audio-output with 24dB/octave (simultaneously usable with 'OUT')

There are six potentiometers with following functions:

Poti-Name	Function	Comment
Frequency	Cut-Off frequency 20Hz to 20kHz	Filter cutoff frequency, range: min := < 20 Hz max := > 20kHz 12 o'clock position := 440Hz
Track	Keyboard-CV tracking potentiom.	Keyboard-CV tracking adjustable 0 := None 1 := 1V/octave
Res.	Resonance potentiometer	Resonance adjustment 0 := None 10 := maximum, self oscillation 12 o'clock position := starting oscillation
IN	Audio input-level attenuator	Level adjustable between 0 ... 2 0 := No audio signal from IN-jack 1 := audio signal Out-level is 1 * IN-level 2 := audio signal Out-level is 2 * IN-level
ResCV	Resonance-CV attenuator	Resonance-CV attenuator 0 := None 10 := maximum
Mod.	Modulation-CV attenuverter	Modulation-CV attenuverter, controlling the amount and polarity of modulation - := negative modulation + := positive modulation 0 := no modulation

Technical data

• size:
  width: 8HP
  depth: 40mm

• power:
  5Volt, 0 mA
  +12Volt, 25mA
  -12Volt, 25mA

• frequency range: 20Hz to 20kHz.

• frequency CV scale: 1V/Oct.

• signal input, AC-coupled signal path.

• modulation inputs, DC-coupled signal path.

• signal input impedance: > 50kOhm.

• signal output impedance: 470 Ohm.

• CV-Input impedance: 100kOhm.

References

• electric druid, Multimode filters Part2
• AN701 Designing Voltage Controlled Filters

License

Hardware:cc by-nc-sa 4.0 (details)