Simple Envelope Follower Circuit

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BummBummSteffen
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Simple Envelope Follower Circuit

Post by BummBummSteffen »

Hi guys, I created a simple circuit for an envelope follower. I want to use it for side chain compressing (ducking) in the world of modular based techno. The readings on the oscilloscope and the resulting sound are satisfying. I tested it on breadboard with two different inputs: Kick drum audio and an envelope generator.

Do you have any comments on this approach? E.g. something that I should consider in terms of stability or possible interference with other modules?
Schematic_Envelope Follower_2021-12-08-Rev1.png
Thank you!
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BummBummSteffen
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Re: Simple Envelope Follower Circuit

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Re: Simple Envelope Follower Circuit

Post by guest »

looks like you might have your inputs swapped on the first opamp. also, are you using 1M pots throughout to save on different parts? the large resistors add a bit of noise.
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BummBummSteffen
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Re: Simple Envelope Follower Circuit

Post by BummBummSteffen »

inputs swapped on the first opampx
True, thank you! Here's the updated version:
Schematic_Envelope Follower_2021-12-08-Rev1.png
using 1M pots throughout to save on different parts
Tried different values (1k, 100k) and combinations for the fixed resistors and potis. As shown worked best regarding the results on the oscilloscope, they actually gave the smoothest output envelope.
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Re: Simple Envelope Follower Circuit

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definitely R2 should change the envelope performance, but the rest can be scaled if you want. swapping RV2 with R4 might give a nicer response on the pot. the input resistor would have to drop to 10k or so, depending upon what you want for max gain. right now its going from 1 to infinity with a 1/x response, so it wont change much for the first half of travel, and then its going to rocket up at the end.
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notmiserlouagain
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Re: Simple Envelope Follower Circuit

Post by notmiserlouagain »

For gating a Threshold function is needed.
While you have one, via the diode voltage drop, this is fixed at ca. +0.6V.
Imo it would be better to have a level control/gain amp before that point, to vary the threshold...

Correct me if I´m wrong, but R2 looks like the "release" resistor, but cannot really be varied this way. Why not make IC 1.2 a noniverting buffer and R2 to GND, so you can have a variable release, pot or switch?

Out of curiosity, is this an offspring of the Nicolas Collins circuit using CMOS? :tu:
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Re: Simple Envelope Follower Circuit

Post by flashheart »

I'm puzzled. Surely you need to rectify (with the diode) before any smoothing - the Damper part of you're circuit? Or essentially you're just filtering the incoming audio. Or maybe I'm just misunderstanding how RV1, the diode and C2 interact. :despair:
I'm not buying a maths though, not my idea of fun...
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Re: Simple Envelope Follower Circuit

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guest wrote: Wed Dec 08, 2021 12:45 am definitely R2 should change the envelope performance, but the rest can be scaled if you want. swapping RV2 with R4 might give a nicer response on the pot. the input resistor would have to drop to 10k or so, depending upon what you want for max gain. right now its going from 1 to infinity with a 1/x response, so it wont change much for the first half of travel, and then its going to rocket up at the end.
I will try that, thank you!
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BummBummSteffen
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Re: Simple Envelope Follower Circuit

Post by BummBummSteffen »

notmiserlouagain wrote: Wed Dec 08, 2021 2:51 am For gating a Threshold function is needed.
Thank you! I decided to not add a gating function in this design. Want to fit it in 2hp, and my side chaining needs have prio.
notmiserlouagain wrote: Wed Dec 08, 2021 2:51 am Correct me if I´m wrong, but R2 looks like the "release" resistor, but cannot really be varied this way. Why not make IC 1.2 a noniverting buffer and R2 to GND, so you can have a variable release, pot or switch?
I will try that!
notmiserlouagain wrote: Wed Dec 08, 2021 2:51 am Out of curiosity, is this an offspring of the Nicolas Collins circuit using CMOS? :tu:
Nopi, haven't seen those, but will have look :)
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Re: Simple Envelope Follower Circuit

Post by BummBummSteffen »

flashheart wrote: Wed Dec 08, 2021 10:27 am Surely you need to rectify (with the diode) before any smoothing - the Damper part of you're circuit?
Thank you! I came to this design mostly by educated trial and error. I'll try to swap the blocks as you mentioned to see what happens.
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Re: Simple Envelope Follower Circuit

Post by guest »

since those parts are in series, the order does not matter.
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