Envelope follower infrasound trigger trick

Elektron Gear Analog Heat
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There has been multiple threads about more or less successful attempts to trigger LFO restarts via envelope follower or via MIDI CC.

There is another way to do it - with INFRASOUND - sub-20 Hz sinewave pings that are mixed into the incoming audio signal to trigger the ENVELOPE FOLLOWER, that has been set to BASE = infra ping base frequency and WIDTH = 0.

This infrasound sinewave ping is inaudible / filtered high-passed in most audio environments, so it’s technically inaudible, while reliably triggering the envelope follower.

UNFORTUNATELLY, it also inevitably enters the whole audio processing chain inside the AH+FX and beyond and might ultimately cause some nasty issues.

There is currently no FX inside AH+FX that would have cleanly high-passed the incoming audio and got rid of the infrasound while keeping the sub-bass intact. The two options are:

  1. BASS FOCUS - this one allows complete elimination of the infrasound with its LP LEV, unfortunately the lowest XFREQ it goes to is 50 Hz, so its eating your sub-bass as well.

  2. WARBLE - this one has classic Elektron “BASE WIDTH” filter, BASE values above 25 will
    start having meaningful gain reduction impact on 10 Hz wave, however to push it down by 30-40 dB, you would have to go up to 60-90 BASE territory.

FORTUNATELLY, these issues can be easily overcome thanks to the high gain input and high resolution trigger level of the ENVELOPE FOLLOWER!

So the cookbook recipe is as follows:

  1. Make your INFRASOUND sample trigger low volume - around -30 dB on AH+FX input is more than enough.
  2. Set TRIG LEVEL to 100.
  3. Set ENVELOPE FOLLOWER to BASE = frequency of your infra ping (i.e. 5 or 10 Hz) and WIDTH = 0.
  4. Push follower input gain ENV MODE encoder to max. Then turn it down a couple of steps so your input is peaking above the middle on the TRIG LEVEL range but also not yet triggering the envelope.
  5. Add the actual music signal to the input mix. Tweak the settings if necessary so that the music signal without the infrasound is safely below the TRIG LEVEL while the addition of the infrasound to the music signal safely triggers the envelope.

Bon triggérit!

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