Is there a ducking delay project?

[wavley]

I got a guy that I do a lot of work for building amps and stuff and he decided that he really needs an 80's style ducking delay, he only wants the tails to happen at the ends of phrases and stuff.  I know how to do the studio trickery version of this and that you can find this feature in a lot of old multi effects and a few new pedals do it, but this dude likes hand built stuff so I don't really want to tell him to just go buy a Line 6 Echo Park and be done with it.

I thought I had seen someone that had a project for this, but I just can't seem to find it anywhere.

[Kipper4]

Hi Wavley.
There has been some previous discussions.

i used the search perameters

Delay ducking and found Mr Hammer most of the time

[Mark Hammer]

....and it found him again.

Two forms of ducking: one that responds to the space between notes, such that delay only fades in when the player slows down or comes to a halt, and the other based purely on picking intensity.

I imagine they both have their musical purpose or appeal, but they will require different sorts of circuitry.  If you look through the scanned issues of DEVICE on my long-since updated site (hammer.ampage.org), you'll see a schematic from Craig Anderton for a "pluck follower".  That generates a control voltage corresponding to how quickly the circuit is receiving trigger pulses, each trigger pulse being prompted by an envelope follower detecting a new note.

In theory, I suppose, one could generate a sort of envelope follower that is very sluggish and aggregates DC voltage corresponding to envelope over multiple strums/plucks.

I gather another way might be to gate the delay signal.  As long as the envelope is registering above some threshold, the gate is off/closed, and below that threshold the gate opens; presumably with a slow attack so that it isn't jarringly abrupt.

I have an Echo Park and M5, but I haven't listened hard enough to the ducking-delay setting to be able to discern what sort of overall logic it uses to determine when to bring in the wet signal.

[Transmogrifox]

Yeah I can't find it either.  I don't see any "pre-canned" projects for this with cursory search.

This isn't a terribly hard thing to do using well-established basic building blocks.

Take for example a basic PT2399 delay project and a compressor project.  These have all necessary elements needed to duck the delay. 

One simple idea that comes to mind is take the output from a PT2399 and feed it into an LDR/resistor divider.  Drive an LED illuminating the LDR with an envelope follower circuit with relatively fast attack and slow decay.

If you're up for fiddling around with it on a breadboard then I doubt it will take very much to get it working with acceptable results.

If you want the sledgehammer approach I'll post a flash image implementing this on a raspberry PI with a USB audio interface (PCM2902-based like behringer UCA202, cheapest would be to gut the UCA202 and mount it to the PI board).  I currently have some chorus/flange/delay code working on my Rpi which allows assignment of envelope control to anything so making it work as a ducking delay is just a matter of assigning the correct preset -- further refinements are just ASMOP (A simple Matter Of Programming).  The remaining work involved with that is implementing a control interface...haven't decided yet whether I just want a few rotary encoders or ADC's and pots.  Have also considered analog multiplexing voltage readings off pots directly into the audio right channel input.

Of course it could do so much more than a simple ducking delay.  Has a lot of memory, enough for about 1/2 hour of 48 kHz recording directly to RAM, really. 

[Kipper4]

Device 11 thanks Mark.
About 1/3 way down page


http://hammer.ampage.org/files/Device1-11.PDF

[wavley]

Thanks for the help guys.  I think I'll see him this weekend and give options, he just dropped a grand on me building him an amp so I don't know how much he is (or his wife) is willing to spend so soon.  Maybe he's in the paying me for working up a schematic from building blocks, laying out a PCB, and making it or may only be into paying up for what it would be to build an existing project or kit.

The Echo Park may be his answer, he's not a big delay geek like me, he's more of an 80's hair/Joe Bonamassa kind of guy.  I may still try to find the time to build this up out of personal curiosity and love of delays.  He's a good guy and a good customer so I'm not into squeezing every dime out of him, he'll have something else he wants soon enough.  I do appreciate that he comes to me first whenever he wants something, that's actually a pretty good feeling.

[Mark Hammer]

I'll go back to my earlier musings about what sort of ducking he wants.  If he just wants the wet generally on the back-burner until he stops playing, then it could be as simple as a Rebote with a simple envelope follower driving a vactrol.  the LDR of the vactrol is half of a basic passive attenuator that reduces the wet signal more when playing.  That's not too complicated, and throwing together a Rebote is pretty cheap and straightforward.  The suggested add-on wouldn't cut the wet signal off in any sort of "intelligent" way, but would essentially adjust the wet/dry balance (well, the wet level, more specifically), depending on playing, which is in the ball-park.

[wavley]

I'll go back to my earlier musings about what sort of ducking he wants.  If he just wants the wet generally on the back-burner until he stops playing, then it could be as simple as a Rebote with a simple envelope follower driving a vactrol.  the LDR of the vactrol is half of a basic passive attenuator that reduces the wet signal more when playing.  That's not too complicated, and throwing together a Rebote is pretty cheap and straightforward.  The suggested add-on wouldn't cut the wet signal off in any sort of "intelligent" way, but would essentially adjust the wet/dry balance (well, the wet level, more specifically), depending on playing, which is in the ball-park.

Yeah, I'll have to talk to him more about his wants/needs/expectations.

[Transmogrifox]

Considering what kind he wants is you mentioned you know how to do the studio trickery version of this. 

Do you manually fade-in, fade out the echo track or do you use a compressor side-chain (or other method)?

Fade-in fade-out would be more of a triggered mute function while the compressor side-chain would be more of the direct envelope detector feeding a vactrol.  Neither one is very complicated as Mark pointed out.

[wavley]

Considering what kind he wants is you mentioned you know how to do the studio trickery version of this. 

Do you manually fade-in, fade out the echo track or do you use a compressor side-chain (or other method)?

Fade-in fade-out would be more of a triggered mute function while the compressor side-chain would be more of the direct envelope detector feeding a vactrol.  Neither one is very complicated as Mark pointed out.

I like the side chain version, but I'm thinking he want's more of the manual fade way, I think he just wants to hear repeats at the end of a phrase to kinda fill in gaps in playing, but I should check with him first.

[Kipper4]

If that's the case why not build a delay with tails on a momentary switch. As an option.
That's what I did with my rebote 2. Works a treat.

[wavley]

If that's the case why not build a delay with tails on a momentary switch. As an option.
That's what I did with my rebote 2. Works a treat.

That's a pretty good idea too, he might be the kind of guy that likes to manually do that.  Although he's not super big on pedals, pretty much his rig now is an amp I built him and a drive I built for him.