AM1008 Env Amp

The 12HP wide AM1008 is a completely new module that marries a VCA and ADSR envelope generator in the style of ARP 2500 dual modules (e.g. Filt Amp, Mod Amp). The design makes use of 1980’s synth chips to create a simple but elegant design that works well with the AMSynths range of 2500 style modules. The VCA is followed by a “Tanh” overdrive circuit to create warm soft clipping.

AM1008 circuit The AS3381 chip is used to create a linear VCA with the gain controlled by a rotary GAIN control and two CV inputs. The first CV input is attenuated by a rotary potentiometer (CV1 AMT), whilst the second input is normalised to the Envelope Output.

The AS3310 chip is used to create a traditional ADSR envelope generator with the Attack, Decay and Release variable from 1ms to 20 seconds. The envelope stages are controlled by 20mm slide potentiometers with subtle red LED’s. The ADSR can be manually gated ON/OFF with a red push button, or the gate and trigger jack sockets can be used with a keyboard or sequencer to activate the envelope.

The VCA is followed by a soft clipping overdrive circuit that shapes the input signal by adding curves to the waveform. It works best with sine, triangle or sawtooth waveforms, as square waves are already “clipped”. A rotary potentiometer controls the amount of overdrive, which produces gain up to x1.5 times. The input level controls can be used to dial back the gain but still introduce soft clipping. The drive can be dialed down to a low setting with no clipping present.