hmmmm... envelope control of a chorus

[pinkjimiphoton]

just curious, anyone ever try something like this?
my vision is kinda like each attack starting a sweep of modulation, unless ya play legatto and in that case it just sweeps the mod til the next attack.

doable? think is would sound good? i generally hate chorusing, but was thinking this may be kinda cool... wayyyyy above my humble paygrade, but love to see what you smart folks think of this idea.

i mean, should be able to control rate or depth that way and make for a much more expressive effect i'd think... any thoughts?

[Transmogrifox]

From programming/DSP experiments I know that envelope control of depth is really lush sounding.  Also putting a mix between envelope detector and LFO to modulation input is a nice touch.

I think the direct modulation with envelope (replacing LFO with envelope detector) is what you were describing?  Not like the attack triggers an LFO reset, right?  LFO reset on attack would need to be a slow reset so you don't get a discontinuous jump in the delay time.

Anyway, if you have Linux and know how to run real-time FX using JACK I can probably modify my chorus/flanger code to add envelope control and you can mock it up using a digital effect.

Else if you're interested I could wrap the DSP code into a cgi program on my website that works on a sample wav file and produces a processed wav that you can download.  I envision a simple interface where you enter parameters in a field and press "go" and then it processes something like a 20 second wav file with those settings and you can hear it.

Let me know if the DSP mock-up is interesting.  It will probably take me a while to get it done even though I have most of the code laying around...just needs to be all stitched together to make an envelope chorus

Either way I know at least the envelope modulation of chorus sounds really nice and is worthwhile putting it together.  I have some hardware ideas in mind to implement this on (for example) a BBD chorus or THAT other chip.

[pinkjimiphoton]

From programming/DSP experiments I know that envelope control of depth is really lush sounding.  Also putting a mix between envelope detector and LFO to modulation input is a nice touch.

I think the direct modulation with envelope (replacing LFO with envelope detector) is what you were describing?  Not like the attack triggers an LFO reset, right?  LFO reset on attack would need to be a slow reset so you don't get a discontinuous jump in the delay time.

i was thinking each attack starting the cycle, but either way would probably sound pretty cool.  originally i was thinking have the lfo speed up over time to whatever you set the chorus "speed" to. kinda... just thought chorus, flange and phasers would all sound better if they were triggered this way instead of cyclically.

Anyway, if you have Linux and know how to run real-time FX using JACK I can probably modify my chorus/flanger code to add envelope control and you can mock it up using a digital effect.

sadly, i don't know jack

Else if you're interested I could wrap the DSP code into a cgi program on my website that works on a sample wav file and produces a processed wav that you can download.  I envision a simple interface where you enter parameters in a field and press "go" and then it processes something like a 20 second wav file with those settings and you can hear it.

if you are willing and have the time, i would love to hear it, be really curious to see if it's a worthy enough idea to explore, thanks!!

Let me know if the DSP mock-up is interesting.  It will probably take me a while to get it done even though I have most of the code laying around...just needs to be all stitched together to make an envelope chorus

Either way I know at least the envelope modulation of chorus sounds really nice and is worthwhile putting it together.  I have some hardware ideas in mind to implement this on (for example) a BBD chorus or THAT other chip.

i'd love to see what ideas you might have... i just thought it would be a nice way to make over used and generic sounding effects a little more expressive.

i seem to remember having a phaser that reset on each attack decades ago,, by eh maybe? long time ago, but it was a really cool sounding effect.

thanks for the help and advice, i think it could be really a cool thing to develop. i was thinking more analog maybe with a bbd based chorus, but i guess dsp may be the way to go.

[digi2t]

Above my pay grade too, but I'm intrigued...

Could the envelope detection portion from the Mutron III be adapted here, with a vactrol controlling the depth?

I'd be surprised if no one has tried this idea already.

[Transmogrifox]

Hopefully I'll have some time to dig up some code and stitch things together.

I had envisioned a DSP emulation was just a sort of quick easy way to experiment with the idea before you invest the time into wiring stuff together.

Something like digi2t mentioned chaining a Mutron envelope detector to one of the pots on a BBD chorus would be a good start.  Of course to sync the LFO you would probably need a trigger to discharge an LFO cap or something to restart it at zero.  It may be an ADSR circuit from an analog synth is the thing to use here.

It could really grow into a monstrous modulation machine

[armdnrdy]

Do a search for the "Multiflanger" from the Japanese effector book.

This circuit includes envelope in it's design.....and just about everything else!

[garcho]

how about an envelope detector-controlled VCA blend? when you strum the initial attack is clean, then fades out to deep chorusing, or whatever chorus you like, but deep and/or quick would be more dynamic. wouldn't be hard with an OTA.

or you could use an LDR in series with the LFO rate, so it modulates quickly and then slows down as the signal fades. or the other way around.

or you could control the depth of something like the Little Angel with a LDR in series. again, up or down, depending on how you orient the LED driver circuit.

a tap-tempo LFO would be externally syncable.

[Mark Hammer]

I incorporated an envelope follower in a Phase 90.  Since speed is set by a variable 500k resistance, I simply paralleled an LDR with the speed pot.  The rectifier section driving the LED that shines on the LDR is tapped from the input stage (i.e., first op-amp).  The envelope follower is just an inverting stage pushing the LED on its output.  Nuthin fancy.

The trick is nailing down the "right" attack and decay parameters so that the increase in speed as you dig in feels right, and the modulation rate settles back down in a musical manner.  But once you get it right, it's heaps of fun to play with.  Instead of the modulation being just something going on in the background, you get to "work it", the way you'd work an auto-wah or a wah.

Probably the only thing I'd want to envelope control in a chorus is the rate.  With phasers and flangers you can also modulate the feedback/emphasis to give a little more bite when you pick harder.

There've been numerous threads here over the years about envelope-controlled tremolos.  I have a Tonecore Tap Tremolo, and it has envelope control of speed.  Very nice feature.

[Ben Lyman]

how about a regular old fuzz pedal with ldr controlling the gain? play hard with your guitar volume all the way up for max fuzz, turn down your volume and pick soft the gain pot "automatically" turns itself down.
Delay would be cool, infinite repeat-feedback-cricket-wars-in-space until you stop playing.
For a chorus, I think I would want the depth to vary with the volume of the notes

[anotherjim]

It can sound interesting. I did one containing it noted here.
http://www.diystompboxes.com/smfforum/index.php?topic=110748.msg1017026#msg1017026
That used micro-controller behaving like a BBD, so any BBD Chorus or Flanger with a VCO for the clock should be easy to work. The Hollis designs using the CD4046 as clock for instance (Zombie Chorus?). Mix the envelope follower output with the LFO by resistors or blend pot.
You would need an amp to feed the envelope since BBD circuits don't give a lot, if any, gain from their input amp/buffer.
Find the sound clips with "envelope" in the title here...
https://soundcloud.com/ashdalestudio/sets/avr-8bit-delay-multi-fx
Should mention...
Unlike pure LFO modulation which is obviously cyclic, envelope control, being slow and mostly one way, can give a bending out-of-tune effect in some settings. It shows on some of those clips (at least, I don't think it's all my playing to blame!)

[pinkjimiphoton]

Above my pay grade too, but I'm intrigued...

Could the envelope detection portion from the Mutron III be adapted here, with a vactrol controlling the depth?

I'd be surprised if no one has tried this idea already.

that was one of the things i wondered too, maybe even something stupid like one of tim escobdo's phunqgnosis or something.... so you can control the speed of the chorusing  with your technique.. seems it would be a real expressive way to get freaky right quick.

[pinkjimiphoton]

I incorporated an envelope follower in a Phase 90.  Since speed is set by a variable 500k resistance, I simply paralleled an LDR with the speed pot.  The rectifier section driving the LED that shines on the LDR is tapped from the input stage (i.e., first op-amp).  The envelope follower is just an inverting stage pushing the LED on its output.  Nuthin fancy.

The trick is nailing down the "right" attack and decay parameters so that the increase in speed as you dig in feels right, and the modulation rate settles back down in a musical manner.  But once you get it right, it's heaps of fun to play with.  Instead of the modulation being just something going on in the background, you get to "work it", the way you'd work an auto-wah or a wah.

Probably the only thing I'd want to envelope control in a chorus is the rate.  With phasers and flangers you can also modulate the feedback/emphasis to give a little more bite when you pick harder.

There've been numerous threads here over the years about envelope-controlled tremolos.  I have a Tonecore Tap Tremolo, and it has envelope control of speed.  Very nice feature.

mark it's stuff like this that makes us all love and respect you so much. nice!!!

[Mark Hammer]

Thanks, Sir James.  Much appreciated.

[garcho]

thanks Jimi, wasn't even on my radar, and it's getting in the way of 4 other builds, but what can you do, i already started this on my breadboard with a revamped little angel. i think i'm going to implement 2 envelope mods with a Q&D envelope follower and see how they work, the obvious ones - depth and rate.
my immediate reaction to the sound of guitar through chorus is usually somewhere between gag and projectile vomit, which is sad, because it is easy to use a chorus tastefully. i've really been digging medium-ish distortion into a stuck wah into chorus with the rate low to medium and the depth up for a rock-y improv group i've been playing in recently. this will do nicely...

[midwayfair]

I did an analog chorus running on a charge pump based on my Blue Warbler and the microchorus with a vibe switch. I even have a PCB for it that fit in a 1590B (!). Unfortunately, I screwed up the LFO and did a few other things wrong regarding the current draw, and I never got another set of prototype PCBs to actually verify it. It worked on the breadboard, though.

Jimi, if you want the schematic and board files, PM me.

[Mark Hammer]

thanks Jimi, wasn't even on my radar, and it's getting in the way of 4 other builds, but what can you do, i already started this on my breadboard with a revamped little angel. i think i'm going to implement 2 envelope mods with a Q&D envelope follower and see how they work, the obvious ones - depth and rate.
my immediate reaction to the sound of guitar through chorus is usually somewhere between gag and projectile vomit, which is sad, because it is easy to use a chorus tastefully. i've really been digging medium-ish distortion into a stuck wah into chorus with the rate low to medium and the depth up for a rock-y improv group i've been playing in recently. this will do nicely...

Personally, I am pleased to see the presence of "mix" controls on more and more choruses these days.  Not just for being able to dial in vibrato sounds, but for also being able to dial in subtler chorus effects.  Much of what evokes the "between gag and vomit" response to chorus is the superthick sounds that make one feel like they are imprisoned or constrained by the effect, rather than being allowed to be more expressive via it.  Another part of what makes choruses less overbearing is trimming the bass and lower midrange, such that the delay path is mostly stuff above, say 500hz.  Between the bass cut and the lower mix level, it allows choruses to yield more swirl and less annoying wobble.

[garcho]

mine is at 75% wet, usually. but can go from 33% to 100% depending on band/song. i wouldn't want a chorus without wet/dry blend control. i love subtle chorus, like depth at half, rate so low it's not there, and about 66% wet. maybe a little skosh of extra delay time. or really quick rate but almost no depth, maybe 50% wet. a bit of shimmer. i'm excited about having an envelope chorus that goes from clean to very wet after a medium-rate delay. king tubby would be proud of us

[Mark Hammer]

Here's a demo of what envelope control can do for a chorus.  I wasn't aware of this pedal until today.

[Transmogrifox]

Very nice, mark.  Something worth trying some time.

FYI, I am working on some code.  Just an update on progress I have it reading/writing wav file and for kicks does a tremolo just as proof of concept. This is pretty much the backbone of the function and most of the new code, so it should be pretty straightforward to implement the rest.

Now I just need to stitch in some chorus code and envelope control.  Probably the time consuming/tedious part will be writing the web CGI interface to allow assignment of envelope control to anything.  I'm thinking a field on each parameter (depth, width, mix, LFO rate) just entry box where you enter gain for envelope which can be negative or positive (envelope makes it move down or up).

Stay tuned, it's coming.

[StephenGiles]

Jimi - "have the LFO speed up over time" makes me think once again of the EH Spacedrum envelope generator - arguably one of the smoothest, which, energised by a suitable trigger signal extracted from guitar input, could be used to provide voltage control of say an opto strapped accross the LFO's rate pot.

I'm also thinking Maestro Stage Phaser which had a Motor Stop/Start simulation circuit
http://www.aronnelson.com/DIYFiles/up/maestro_stage_phasor_MPP-274A.pdf