AM8120 VCF & VCA

OVERVIEW The AM8120 is a replica of the Roland 100M 120 module, a prototype that Roland made in 1978 but without taking it into production. It was a combination of a VCF and a VCA in the same module. The original 120 has been re-imagined by using the filter from the Jupiter 8 and the VCA from the 100M, this ensures a different sound to the 121 dual filter. 

DESCRIPTION The Jupiter 8 style VCF is based on the AS3109 chip with a slide switch to select either 12 and 24dB filter modes. Q compensation has been implemented to ensure there is no signal level drop at higher resonance settings. The filter is trimmed to just touch into self oscillation at the maximum resonance setting.

The VCA circuit is the same as the original, with exponential and linear response modes selected by a slide switch. The output of the VCF is normalised into the first signal input of the VCA.

There are trimmer pots for the audio and CV inputs, slide pots for frequency cutoff and resonance, and a rotary pot for VCA gain. The module is designed to work with audio signals up to 10V p-t-p and CV signals from 0 - 10V. There are green and red LED's on both the VCF and VCA, which represent signal active and signal overload.

CONNECTIONS There are 16x 3.5 mm jack sockets on the base of the front panel:

• 3x VCF audio inputs
• 2x frequency cutoff CV inputs
• 1x resonance CV input
• 3x VCA audio inputs
• 3x VCA CV inputs
• 2x VCF outputs
• 2x VCA outputs

The module comes with a set of M3 mounting screws and washers, and a standard Doepfer power cable.