What's the best envelope follower (no filter, just the follower itself)

[Taylor]

I'm building a big modular box and I want to have some controllers which can modulate the effects in complex ways. It seems that the Tremulus Lune is the king of LFOs, with all the spacing and waveshaping options. I'm looking for the equivalent "king of envelopes".

Offhand, I can't think of what features an ideal envelope would have. I must confess that I haven't been too into envelope filters, because of their ubiquity in shlocky music, so I haven't paid much attention to envelopes.

I guess I'd be looking for something with up and down envelopes, and some sort of attack and decay controls. Any ideas what effects have the best envelopes to plunder?

[StephenGiles]

When it's finished my Adaptive Space Filter envelope generator should be up there, but unfortunately few folks seem interested further than their fuzz boxes, sad to say. Meanwhile, I gather that the Harry Bissell envelope gnerator is pretty good.

[frequencycentral]

Some god ideas here: http://moosapotamus.net/IDEAS/stompboxology/EnvelopeEffects.htm

[Mark Hammer]

There are two generic kinds of envelopes: that generated by the input signal itself, and that triggered by the input.  In the latter, since it is produced by a function generator, there are many more options for adjusting the rise/attack time, as well as for having a smooth, ripple-free decay (the bane of many envelope-controlled effects).  The shortcoming, of course, is that unless it is a more complex circuit, it is largely unresponsive to a number of qualities about the input signal, such that you can initiate it but can't really control it in real time.

The first kind - a true envelope follower - has some challenges.  One is that it produces its output by integrating signal information over time.  The global result is that one (almost) always has to trade off response time against smoothness.  If you want it smooth, you nearly always have to accept a sluggish attack (not a gradual swell but not whip-crack fast either), and if you want fast you often have to live with the burblyness if a decay contaminated with ripple.  Still, it is something the user controls in real time, and can implement feel more effectively than with something using fixed parameters.

One way to get the best of both worlds is to use an envelope follower set to respond fast in both rise and fall parameters.  Personally, I find that envelope-controlled effects tend to sound more "synth-ey" when the decay time is set fast.  Happily, since the greatest risk of audible ripple is in the dying moments of a strummed note, choking things off early means you never hear it.

Convention/tradition/experience says that "best" envelopes are those produced via full-wave rectification.  I think I wrote enough about that in my "Technology of Envelope-Controlled Filters" document, available on GEOFEX or on my site (http://hammer.ampage.org).

I too would recommend Harry Bissell's envelope follower circuit.  It's more complex than the usual beast, but pays big dividends.  I had the pleasure of playing Harry's all-analog home-brew guitar synth a half-dozen years ago, which uses that circuit, and I have to say it was an extremely responsive instrument.  Very organic-feeling.

Ultimately, though, every circuit used to produce "musical event" information needs to be considered in light of what it is you are trying to use it for.  Some are better suited to some purposes than others.

Some god ideas here: http://moosapotamus.net/IDEAS/stompboxology/EnvelopeEffects.htm

Well, I don't know if Charlie holds himself in that high regard, but yeah, there are some good ideas there.

[frequencycentral]

Some god ideas here: http://moosapotamus.net/IDEAS/stompboxology/EnvelopeEffects.htm

Well, I don't know if Charlie holds himself in that high regard, but yeah, there are some good ideas there.

Hmm, a bit like using a 0.01uf when you should have used a 0.001?

Note to self: try to type with eyes open.

[Mark Hammer]

Do you have any idea how many times I have typed the word "public" in a document and it came out "pubic"?

[anchovie]

Do you have any idea how many times I have typed the word "public" in a document and it came out "pubic"?

I know someone who wrote an email to a French girl that he fancied and wanted to impress her by starting it with "Salut!".

In his excitement, he left out the 'a'.

[earthtonesaudio]

One thing that seems promising is double-full-wave-rectification (as suggested by R.G. once) as a way to get more "smoothness" from the envelope.

[StephenGiles]

Ultimately, though, every circuit used to produce "musical event" information needs to be considered in light of what it is you are trying to use it for.  Some are better suited to some purposes than others.

Perzacerly!

As I often say, to impress the girl that you have lured into your music room - the Adaptive Sweep Generator which follows the guitar peak in attack and cannot ripple in decay is just the job, but in a band I should think something very simple - if you must use it in a band

[StephenGiles]

One thing that seems promising is double-full-wave-rectification (as suggested by R.G. once) as a way to get more "smoothness" from the envelope.

It could be worth foregoing the obligatory 1590 box and trying quadruple full wave rectification or an adaptive comparator, the pulse output of which follows the instantaneous peak output of your guitar, is sampled and used as the start frequency control voltage........................where have I heard that before

[deaconque]

Honestly this stuff is way over my head but would an ADSR type module from a modular synth work for this purpose?  I know modular synths are voltage controlled but it seems like there would be some way of modifying that to this type of situation.

[Taylor]

Well, an ADSR would be fun, but it isn't an envelope follower. It would be possible to derive a trigger from an audio input and use that to start an ADSR, but it won't have any correlation to the instrument's dynamics.

[Taylor]

Ultimately, though, every circuit used to produce "musical event" information needs to be considered in light of what it is you are trying to use it for.  Some are better suited to some purposes than others.

But the hitch here is that I'm building this in the style of a modular synth. I want the envelope as a buillding block so that, down the road, if I feel the need to control delay time, or trem speed, or ring mod frequency with my input envelope, I can patch it up that way. So I'm not able to select the circuit for the purpose.

Can you give me any examples of the latter type you mention - are these at all related to envelope, or really just audio-triggered ADSRs?

[Mark Hammer]

Then consider this one: http://www.synthdiy.com/files/2004/PAIA_2720-11_Env_Follower.gif

It will give you a full-wave rectified envelope signal, plus a trigger output that can be used to initiate envelope generators.  Best of both worlds.

[nelson]

I like the envelope generator in the meatball. It uses standard silicon diodes, has a low parts count and if you want a trigger just change the last buffer stage to a comparator. The attack and decay range are also easily modified.

[StephenGiles]

Then consider this one: http://www.synthdiy.com/files/2004/PAIA_2720-11_Env_Follower.gif

It will give you a full-wave rectified envelope signal, plus a trigger output that can be used to initiate envelope generators.  Best of both worlds.

Could comparator IC4 perhaps be made adaptive so that when the voltage presented to  IC4-pin 3 is sufficient to trigger the comparator, it's peak voltage output is proportional to the aforesaid voltage at pin 3 - I wonder on this beautifully sunny Sunday afternoon?

[puretube]

The neverending thread... 

[Cliff Schecht]

Then consider this one: http://www.synthdiy.com/files/2004/PAIA_2720-11_Env_Follower.gif

It will give you a full-wave rectified envelope signal, plus a trigger output that can be used to initiate envelope generators.  Best of both worlds.

PAiA will be bringing this circuit back in the near future. It's a great little circuit that's well tuned for guitar-type inputs.