Sometimes the interaction between a modular system and other musical instruments (electronic or acoustic) is needed. With an envelope follower circuit we can achieve a direct control of the amplitude of the signal.

It will produce a control voltage proportional to the amplitude, allowing real communication between our system and the external sound source.

Befaco's Instrument Interface DIY module has the following blocks:

“PREAMP”
With two audio inputs (6.5 jack and Minijack/banana), input apmlification is controlled with the “GAIN” pot, controlling the amplitude of the envelopes that will be generated.  The minimum signal required to generate the maximum envelope is 200mV peak and allows up to 5V input.

“BPF”
The signal will pass thru a band pass filter with cutoff frequency and band width control via “FREQ” and “WIDTH” pots, allowing you to select the frequency range that will generate your control signal.  After this stage the signal will be output at modular synth level via “AUDIO OUT”.

“ENV.FOLLOWER”
After filtering the signal it will feed the “RESPONSE” stage, determining the envelope follower response velocity. It features a “HIGH”, “MEDIUM” and “lOW” selector switch to get an optimal envelope for different kind of signals. “FOLLO OUT” will output the extracted envelope and show us its level via a LED. Green: Medium level, Orange: High level and Red: Max. Level.

“ENV.REGENERATOR”
“REGE OUT” is a re-generated envelope that will allow controlling the rise of the evelope with “ATTACK” and the fall with “DECAY”, making them longer or shorter.
It features a LED indicator for the regenerated evelope level. Green: Medium level, Orange: High level, Red: Max. Level.

“TRIG.EXTRACTOR”
With the “THRESHOLD” pot we control the level of a comparator that determines when “GATE OUT” and “TRIGG OUT outputs will be activated. “GATE OUT” will be at high level while the envelope is over the threshold we set, while TRIGG OUT is present just when the threshold is passed.  Indication LEDS will show when the outputs are active.