Threshold rec — threshold-initiated sample recording

This is a utility patch I wrote during beta-testing, with the purpose of recording “clean” samples (i.e. samples which started with the audio, rather than a silence that might occur between me pressing the record button and then playing a sound). Recording is armed, first, and then recording begins properly when a minimal audio level threshold is exceeded.

The process is pretty simple:

Adjust the orange Threshold control as you run audio into ZOIA. A mango pixel called Threshold Cross will light up when the audio exceeds the threshold, so you can calibrate accordingly.

Press the white Record Arm button. The button will light up once pressed.

When the incoming audio exceeds the threshold, the red Recording pixel will light up.

To end the recording, press Record Arm again.

The green Play button lets you review the sample.

Personalize it:

If you would rather use a stompswitch or a CV signal to arm recording, connect a momentary stompswitch or CV input to the second page. A stomp or gate/trigger will arm the recording, and a subsequent stomp or gate/trigger will end the recording.

If you would rather use a MIDI signal to initiate the recording, place a MIDI note in module and connect its gate output to the sample and hold input on the second page. Delete the envelope follower on the second page, or the comparator, or both, or disconnect any of those modules from any destination they have — this will disable the audio threshold recording circuit.

If you would rather use a CV signal passing a threshold to initiate recording, connect a CV input to the positive input of the comparator on the second page. Delete the envelope follower, or otherwise disconnect it, for the reasons given above. The Threshold control on the first page will control the CV threshold, just as it did an audio signal, and the pixel will light accordingly when that threshold is crossed.

And that’s it. If you’re copying the circuit to another patch, make sure you get both pages (the “mechanics” are on the second page). Here is a description of the circuit, originally provided as a comment on this post on r/ZOIA:

“Stompswitch/pushbutton (momentary) –> flip flop

This “arms” the recording; after this, the recording will begin once the threshold is passed. When we press the pushbutton or stompswitch, the flip flop goes high, which sets a high value at the sample and hold input.

Flip flop –> sample and hold input

Audio input –> envelope follower
Envelope follower –> positive input of comparator
Bias negative input to set threshold

This sets our threshold. We don’t need to get very fancy with the envelope follower/comparator configuration because we are just looking for the first moment the threshold is crossed, which will essentially produce a trigger.

Comparator –> sample and hold trigger input
Sample and hold –> sampler (or looper; I developed it for the looper module, but it works the same way) record input

So our sample and hold goes high as soon as the threshold is crossed. That sends a record signal to the sampler input. You might want to place a buffer delay before the sampler, to make sure the threshold crossing is aligned with the sampler input signal, but this is a difference of 1.33 ms, so in a lot of cases just fine-tuning the threshold value works for me.

Stompswitch/pushbutton (same as above) –> multiplier input 1
Sample and hold –> multiplier input 2
Multiplier –> sample and hold trigger input

So, this is the part of the circuit that ends the recording. The flip flop goes low, because the stompswitch/pushbutton triggers again, and then, the sample and hold trigger input is triggered only when the sample and hold is high (the multiplier works as an AND gate just fine, but you could use the new logic module to create this part of the circuit, if you wanted to toy around with that); since the flip flop has dropped back to zero, the sample and hold samples zero and the recording ends.”

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  • Category: Sampler Utility
  • Revision: 0.1
  • License: Creative Commons Attribution Share Alike 4.0
  • Modified: 8 months ago
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