Befaco ‘I² – ‘Instrument Interface’ – Panel / PCB Set

£30.00 (Excl. VAT)

A versatile instrument input module with Preamp, Envelope Generator, Trig extractor and more.

This a Panel / PCB set only – for a full kit go here

Befaco Parts available here 

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SKU: PP_Befaco_Instrument_Interface Categories: , , Brand:


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 a real communication between our system and the external sound source.

The Instrument interface module has the following blocks:

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

The signal will pass thru a band pass filter with cutoff frequency and band width control via “FREQ” and “WIDTH” pots.
Like this we will select the frequency range that will generate our control signal.
After this stage the signal will be outputed with synth level via “AUDIO OUT”.

After filtering the signal it will feed “RESPONSE” stage, that will determine 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 otput the envelope extracted and show us it’s level via a LED. Green: Medium level, Orange: High level and Red: Max. Level.

“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.

With “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.


  • Compatible Eurorack
  • Power supply:  +/-12V.
  • Current: +12V: 40mA -12V: 35mA.
  • 11 HP.  45 mm depth.

Assembly manual | Schematics PDF 

Additional information

Weight 0.0741 kg
HP Size

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