AM4012 Low Pass Filter

OVERVIEW This 12HP module is a re-imagining of the ARP 4012 low-pass filter constructed around a traditional “Moog” transistor ladder. It has a wide cutoff range between 0 - 35kHz and goes into slef oscillation across the frequency range. The 4012 module first appeared in the ARP 2600 synthesizer in 1971, and it is a refinement of the 1006 filter in the 2500 Modular synthesizer.

DESCRIPTION The AM4012 has been engineered with additional features to provide the best ARP  style voltage controlled filter in Euorack. Additional features include:

• Voltage controlled resonance 
• Q compensation
• Keyboard percussion, called PING

External voltage control of resonance enables more control over the sound of the filter in realtime, whilst the Q compensation averts the drop out of the audio signal at high Q settings. The PING feature enables keyboard percussive sound to be created from a gate signal when the filter is self oscillating.

CONNECTIONS There are three 3.5 mm jack sockets on the base of the anodised aluminium front panel:

• SIGN IN 1 & 2 - Audio inputs with individual level control
• KYBD - 1/V octave CV input for filter cutoff, designed for keyboard pitch input
• FMOD - CV input for frequency ciutoff modulation
• QMOD - CV input for resonance modulation
• PING - Eurorack Gate signal for "pinging" the filter resonance
• OUTPUT - Audio signal output

There are slide potentiometers for adjusting frequency and resonance modulation and rotary potentiometers for adjusting frequency cutoff and resonance. A trimmer pot adjusts the final resonance of the PING feature/

The module comes with a set of M3 mounting screws and washers, and a standard 10 to 16-way Doepfer power cable.

PRODUCTION STATUS: IN DEVELOPMENT