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 Forum index » DIY Hardware and Software
DIY Envelope Follower
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julianw



Joined: Jul 30, 2007
Posts: 78
Location: UK

PostPosted: Wed Feb 20, 2008 6:07 am    Post subject: DIY Envelope Follower
Subject description: For Moog Moogerfooger/Mutronics Mutator/Daft Punk style filter modulation
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Hello All,

Could anyone here help me out with a suggestion for a DIY envelope follower circuit, where audio signals could be fed through it to produce CV outs (+ inverted outs?) to control cutoff and resonance of filters (or whatever Smile )

I'm trying to process filtered drum/sampled loops through my modular, this stuff is dead easy to do in software, but modular sounds a zillion times better, I'm sure there is a really simple solution which evades me.

Thanks In Advance,
Julian
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RF



Joined: Mar 23, 2007
Posts: 1490
Location: Northern Minnesota, USA
Audio files: 28

PostPosted: Wed Feb 20, 2008 7:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Julian
I built this one....
Add an inverting output and you are good to go.
[EDIT ]
I don't recall which op-amps I used - probably TL072 or TL082....
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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
Location: NYC

PostPosted: Wed Feb 20, 2008 9:16 am    Post subject: Reply with quote  Mark this post and the followings unread

There is the Digisound 80 Envelope Follower, also, which is probably very similar to the polyfusion (but also has a PCB layout):

http://www.digisound80.co.uk/digisound/modules/80-13/80-13.htm
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synth_ollie



Joined: Sep 11, 2006
Posts: 149
Location: sweden

PostPosted: Wed Feb 20, 2008 11:25 am    Post subject: Reply with quote  Mark this post and the followings unread

here´s the paia 2700 series env foll,

simple, but I dont know if it s any good....


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numbernone



Joined: Aug 16, 2006
Posts: 477
Location: new york city

PostPosted: Sun Feb 24, 2008 7:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Anybody have any insight into the type of switch specified in the polyfusion design (ST2-6). Is this similar to the mythical C&K 7211?
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RF



Joined: Mar 23, 2007
Posts: 1490
Location: Northern Minnesota, USA
Audio files: 28

PostPosted: Sun Feb 24, 2008 9:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbernone wrote:
Anybody have any insight into the type of switch specified in the polyfusion design (ST2-6). Is this similar to the mythical C&K 7211?


Use any Double Pole Double Throw Center off toggle switch. Wiring it the way shown gives you three positions of 'on'.
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Thomas Henry



Joined: Mar 25, 2007
Posts: 298
Location: Southern Minnesota
Audio files: 2

PostPosted: Sun Feb 24, 2008 10:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ever considered the NE570? Use both sections in series for double-rectification, and then you can raise the smoothing filter cutoff for faster response.

Thomas Henry
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RF



Joined: Mar 23, 2007
Posts: 1490
Location: Northern Minnesota, USA
Audio files: 28

PostPosted: Mon Feb 25, 2008 5:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Thomas Henry wrote:
Ever considered the NE570? Use both sections in series for double-rectification, and then you can raise the smoothing filter cutoff for faster response.

Thomas Henry


Could you expound a bit on this Thomas?

Thanks,

bruce
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Tim Servo



Joined: Jul 16, 2006
Posts: 924
Location: Silicon Valley
Audio files: 11

PostPosted: Mon Feb 25, 2008 10:09 am    Post subject: DIY Envelope Follower Reply with quote  Mark this post and the followings unread

Of course, if you want the ULTIMATE envelope follower, there's a design by Harry Bissell that uses three similar sections to acheive fast response time AND low ripple on the output:
http://www.edn.com/article/CA265499.html

Harry's quite big on guitar synths, so my guess is that this design is part of his rig. Looks interesting, although I've never heard any build results. Also, it contains no BBDs. Wink


Tim (also has low ripple) Servo
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sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Tue Mar 29, 2011 3:54 am    Post subject: Reply with quote  Mark this post and the followings unread

A friend of mine asked me about what it would sound like to run a voice through an envelope follower controlling a synth. I didn't have one so I built the simple Digisound one from this thread last night.


Thoughts about this schematic:

- It works OK... there's a lot of AC bleed-through as higher input levels (ripple?)

- I think it would be good to implement the Polyfusion's switchable response time.

- The voltage output was low so instead of using a 51K resistor for R14, I put in a 120K. With 120K, When I use my Blacet uLFO to generate a 587Hz (D5) 2.86v p/p triangle wave at the AC input, the output of the envelope follower is 5V.

Samples:

For these two samples, the envelope follower is going to a VCA, the Exponential-FM input of the VCO and the frequency input of my Blacet Filthy Filtre.

Here's what it sounds like with my voice on the input signal:

http://sneak-thief.com/modular/test-envelope-follower-voice.wav

Same thing except with a drum loop instead of my voice:
http://sneak-thief.com/modular/test-envelope-follower-drums.wav

Don't mind the ground loop hum - this module isn't properly grounded yet Wink

Here's the ugly little thing that I cobbled together quickly using whatever spare parts I had lying around:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

I had to try out a few different resistor combinations after everything was already soldered in, hence the funny layout and willy-nilly resistor placement. Also, the leads from the caps aren't soldered to a switch so I could twist them together on the fly to test out different response times.

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LFLab



Joined: Dec 17, 2009
Posts: 178
Location: Rosmalen, Netherlands

PostPosted: Wed Apr 06, 2011 5:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Haven't checked out the samples (at work now), but I've built the Digisound envelope follower as well (on the original huge layout).
Not very happy with it, and since finishing it I've also bought a Analogue Systems RS30 which has a envelope follower which I am also not thrilled about.

Beginning to suspect the following of envelopes is not exactly a trivial matter.

Maybe it just has to be VERY slow (for bassguitar at least) and is that the reason vactrols are often used.

The Bissell one is quite "involved" it sort of a sampler, with three rectifiers being scanned using a 4017 counter. Do want to try that one sometimes, but I suspect that's also too clean and too fast (again for bassguitar).

as for other options, there's the Buchla 230A schematic, which is apparently very fast and has a lot of bleedthrough. And the ARP follower.
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sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Wed Apr 06, 2011 5:17 am    Post subject: Reply with quote  Mark this post and the followings unread

It's slow because you didn't try smaller cap values like in the polyfusion schematic. Even the digisound schematics mention using smaller cap values for faster times.

I highly recommend this mod - it's quite easy and only requires a DPDT on-off-on switch.

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LFLab



Joined: Dec 17, 2009
Posts: 178
Location: Rosmalen, Netherlands

PostPosted: Wed Apr 06, 2011 5:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Actually started with a smaller cap and wanted to use a center off switch to switch additional caps in parallel.
Didn't like it with the small cap, and not a lot with bigger caps.
I did use "modern" opamps, maybe that's the problem.
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sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Wed Apr 06, 2011 5:26 am    Post subject: Reply with quote  Mark this post and the followings unread

JarnoBassplayer wrote:
Actually started with a smaller cap and wanted to use a center off switch to switch additional caps in parallel.
Didn't like it with the small cap, and not a lot with bigger caps.
I did use "modern" opamps, maybe that's the problem.


Do you remember how small? The Polyfusion goes down to .015uF.

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sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Sat Apr 30, 2011 4:37 am    Post subject: Reply with quote  Mark this post and the followings unread

RF wrote:
numbernone wrote:
Anybody have any insight into the type of switch specified in the polyfusion design (ST2-6). Is this similar to the mythical C&K 7211?


Use any Double Pole Double Throw Center off toggle switch. Wiring it the way shown gives you three positions of 'on'.


No, that wiring doesn't make any sense for an on-off-on switch.

An ST2-6 is an on-on-on switch: http://www.apem.com/pdf/ST-series.pdf

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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
Location: NYC

PostPosted: Sun May 01, 2011 8:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

I can completely relate to what you're saying about envelope followers with bass guitars. I find that it's very difficult to get a powerful response from the follower without turning the gain up so high that bass starts to distort.

By far the best, and really the only great envelope follower that i've found for bass and keys is the MuTron III. It's what Bootsy Collins and Stevie Wonder used, and was probably the first EF/VCF pedal device. I don't know if it's the EF (which uses vactrols) or the filter, or probably a combination of the two, but something about it makes this circuit work way better than just about any other-- and I've tried many of them-- Boss, Ibenez, EH, Moog, many modular circuits, etc. I've read that the EH Q-Tron was designed by the Mutron engineer, Mike Bengal; It doesn't sound the same to me.

There's a MuTron clone on the web called the "Neuton" using the same vactrol circuit. Ive been meaning to build one for ages, but haven't gotten to it yet.


JarnoBassplayer wrote:
Actually started with a smaller cap and wanted to use a center off switch to switch additional caps in parallel.
Didn't like it with the small cap, and not a lot with bigger caps.
I did use "modern" opamps, maybe that's the problem.
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LFLab



Joined: Dec 17, 2009
Posts: 178
Location: Rosmalen, Netherlands

PostPosted: Mon May 02, 2011 1:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Couldn't get my Neutron to work, been meaning to have a look at it yet again (one of my first stompbox projects). An other one to look out for is the McMeat, a work-a-like of the Lovetone Meatball pedal, more options than you can shake a stick at.
All of these use a vactrol, maybe that's the key to a great envelope follower for bass. Don't like the Q-tron too much either, and it doesn't use a vactrol, adding further evidence?
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jordroid



Joined: Jan 17, 2010
Posts: 193
Location: ithaca, new york

PostPosted: Tue May 10, 2011 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

I really like the mu-tron III type envelope filters as well, i had an old one forever and sold it after i finally got a neutron working nicely. It was a bit tricky to get it sounding nice, i tried a bunch of things for the LDR part, settling on a home rolled LED + LDR in shrink tubing. What i found was that i needed a much larger current limiting resistor than RG specifies, probably because the LED i used was brighter than what he tested it with, i'm pretty sure i ended up putting a trim pot in for the limiting resistor. I eventually became very happy with how it sounded, but it took a lot of tweaking. I never got anything good to come out of the H11F3s or CLM6000s i tried.

One thing i don't love about the mu-tron III is how the "gain" pot controls both the gain to the envelope follower AND the audio signal. For the neutron i made i built two separate inverting gain stages, identical to U1a in the neutron schematic, and used one for the envelope follower and one for the audio path, with a pot for both. I like it a lot better that way.

The McMeat is basically a mu-tron III with a bazillion options added, i sort of prefer the simpler mu-tron approach but some of the options could be cool.

Another good stand alone envelope follower that is very simple to build is the one from the MFOS envelope follower project (just U1), it works well with a bipolar supply, and it's easy to add an "attack" pot by changing R1 to a pot wired as a variable resistor and resistor in series, i think i did a 1 meg pot and a 1K resistor and liked it. With the "attack" pot set for a fast sweep a good bit of ripple gets through, which sometimes you want. I also replaced R2 with a pot + resistor in series for a "sensitivity" control, i think i used a 500K pot and 1K resistor, and if i remember correctly i used a 270K resistor for R5. You need to add one more opamp to get an inverted version, but that's no biggie. I've been using this envelope follower to drive a mu-tron II type phasor clone(ish) just now, and it's pretty fun.

jordan
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LFLab



Joined: Dec 17, 2009
Posts: 178
Location: Rosmalen, Netherlands

PostPosted: Wed May 11, 2011 2:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good tips Jordan!

I actually had the dual vactrol in my neutron build RG Keen advises, the Hamamatsu one. But I couldn't find a proper value for Rx.
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StephenGiles



Joined: Apr 17, 2006
Posts: 479
Location: England

PostPosted: Thu May 12, 2011 3:02 am    Post subject: Reply with quote  Mark this post and the followings unread

I used Craig Anderton's Bi-Filter Follower for some years and found it to be excellent, especially on slow sweeps - I dislike the sick duck auto wah sound perhaps more than any other sound!!
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JoeMorris



Joined: Apr 26, 2009
Posts: 160
Location: Brighton

PostPosted: Fri May 13, 2011 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

My Oakley Deluxe EFG seems to work very well.
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JoeMorris



Joined: Apr 26, 2009
Posts: 160
Location: Brighton

PostPosted: Fri May 13, 2011 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

My Oakley Deluxe EFG seems to work very well.
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a_guy_called_tom



Joined: Jun 21, 2008
Posts: 31
Location: mountains

PostPosted: Mon May 16, 2011 12:54 am    Post subject: Reply with quote  Mark this post and the followings unread

i built a eurorack filter/envelopefollower combo based on the neutron design. The envelope follower is not very flexible but it works very well and certainly makes the module as a whole much more interesting than a simple filter. Works very well with perkin elmer vactrols, i used two vtl 5c3/2.


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jnuaury



Joined: Feb 28, 2008
Posts: 162
Location: chicago
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PostPosted: Thu Jun 09, 2011 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Haven't tried this design yet, but will soon as its real compact and simple

http://members.cox.net/synthfred/h_enf121.htm

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