AM1008 Env Amp

12 HP Module | AM1008 Env Amp | User Manual (PDF) | Modular Grid | You Tube

OVERVIEW This 12HP wide module marries a high quality VCA and an ADSR envelope generator in the style of the ARP 2500 dual modules (Filt Amp, Mod Amp). The design makes use of 1980's synth chips to create a simple but elegant design that pairs well with the AMSynths range of 2500 style modules or any Eurorack system. 

The VCA is followed by a "tanh" overdrive circuit to create warm soft clipping, which can be adjusted from nil to a maximum with over 1.5 times signal level boosting.

DESCRIPTION An AS3381 chip is used to create a linear VCA, with the gain controlled by a large rotary 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 envelope stage times between 1ms and 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 push button, or the gate and trigger jack sockets can be used with a keyboard or sequencer to activate the envelope.

The VCA is preceded by a soft clipping overdrive circuit that waveshapes by adding curves to the input waveforms. 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 at over x1.5. The input level controls can be used to dial back the gain but still introduce soft clipping. The drive can be dialled down to a low setting with no clipping present.

CONNECTIONS There are eight 3.5 mm jack sockets on the front panel: 

Voltage Controlled Amplifier

• INA - audio input with level potentiometer
• INB - audio input with level potentiometer
• CV1 - control voltage inputs for amplitude control (with attenuation)
• CV2 - control voltage inputs for amplitude control (with attenuation)
  
• OUTPUT - audio signal output
  
  

Envelope Generator

• GATE - Eurorack compliant +5V gate signal input
• TRIG - Eurorack compliant +5V trigger signal input
• OUT - envelope output (0 to +10V)

There are high quality Alpha rotary potentiometers for adjusting amplifier gain, overdrive and the three input levels. The Envelope Genartor has four 20mm slide potentiometers with subtle red LED's for adjusting the ATTACK, DECAY, SUSTAIN and RELEASE settings of the envelope. A manual red push button activates the envelope, with gate status shown on a red LED.

A second red LED is used to illustrate the output signal level of the VCA. It will glow bright red when the signal is more than 10V p-t-p.

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

PRODUCT STATUS: PRODUCTION