delay feedback momentary mod

[jonboper]

I've read through many posts where this is described but am not sure I'm getting it. As a visual person the best way for me to understand is through pictures, all of which are inconveniently MIA in all of the posts describing this king of thing. Is this the correct implementation?

[duck_arse]

yr attk pot is missing a connection, to something. are you trying to do a burst/momentary override of a pot setting? or are you trying to have the attk pot setting momentarily replace/override the fdbk setting?

more info please.

[jonboper]

Thanks for the reply duck_arse.

I am trying to do a burst/momentary override of the feedback pot of a delay to create self-oscillation (on a Madbean Cave Dweller, if it matters).

I've seen this mod on a lot of delay pedals and have read that shorting lugs 2-3 of the feedback pot with a momentary switch will create the desired effect.

I've also read that putting a pot on the momentary switch will allow some control over the attack time or speed of the oscillation.

Yep usually shorting pin2 and 3 works. You could consider adding a couple 1N4148 back to back from pin 2 to ground if the volume of oscillation is too loud. And you could also add a trimpot as a variable resistor to adjust how fast it goes into oscillation (a 10k trimpot for example, going from pin 2 or 3 to the momentary footswitch)

You can also try and short between pin3 and the next resistor in line after pin2. I can't really remember. But I usually just short pin 2 and 3 and include a trimpot.

This diagram is me attempting to understand the implementation...

[duck_arse]

err, okay. disconnect the wire from the mom to fdbk 2. connect attk 1 to fbck 2. that will "work", might not float your boat. if so, try connect attk 1 to fbck 1 instead.

you might need to swap wires 1 to 3, as I don't know your 123 from my CW W CCW.

[jonboper]

disconnect the wire from the mom to fdbk 2. connect attk 1 to fbck 2. that will "work", might not float your boat. if so, try connect attk 1 to fbck 1 instead.

Thanks for the details...can you explain this again...I'm not sure I understand. Sorry to be so basic, but I'm really trying to get what everything is doing and am not there yet.

[moid]

Hi jonboper

I think I've drawn what duck said... his first version looks like this:



and the second option looks like this:



but I might have got that arse_about_duck... our feathered friend will know

[Addy Bart]

Get some alligator test leads. You can try out both suggestions without the hassle of soldering things together then.

If it was me, I'd use a trimpot (try a 10k or 25k) and keep the control inside the enclosure. Connect feedback lug 2 to trimpot lug 2, and go from trimpot lug 1 to the momentary switch. The other lug on the momentary goes to feedback lug 3. Then set the trimpot so the momentary switch works without running away too quickly.

[jonboper]

Wow thanks all, incredibly helpful. I will test out and report back with best configuration for posterity.

[pinkjimiphoton]

what bart said.

when i want to do this (and i do it on a lot of delays i build) i just put a momentary normally open switch across the feedback pot. done deal. step on the switch, it starts to feedback. let go of it, and it fades back to whatever the setting on the pedal is. works great, easy breezy and no hassles at all.

[Ben Lyman]

I'm with Jimi, a single momentary switch, no extra parts, it oscillates when you hold it. Here's a link to a more complicated version I just finished. It has a 3PDT momentary footswitch that is wired up to change 4 different connections simultaneously.
http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg1105961#msg1105961

[duck_arse]

moid's diagram has me covered. thanks.

[jonboper]

I'm with Jimi, a single momentary switch, no extra parts, it oscillates when you hold it. Here's a link to a more complicated version I just finished. It has a 3PDT momentary footswitch that is wired up to change 4 different connections simultaneously.
http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg1105961#msg1105961

Ben, in that demo are you turning something with your foot?

[Ben Lyman]

Ben, in that demo are you turning something with your foot?

No, just trying to control the angle of my shadow. I'm still getting the hang of this thing, there's a learning curve, lol. I have since replaced the blue LED with a super bright white LED and it works much better now, the light reflects off the bottom of my shoe and back down on the LDR really good, even in a pitch dark room

[duck_arse]

I'm with Jimi, a single momentary switch, no extra parts, it oscillates when you hold it. Here's a link to a more complicated version I just finished. It has a 3PDT momentary footswitch that is wired up to change 4 different connections simultaneously.
http://www.diystompboxes.com/smfforum/index.php?topic=36392.msg1105961#msg1105961

in this clip, it's like you're trying to bash that riff into submission, but it just keeps coming back at you, even tho you grind it underfoot. vrr amusing.

[EBK]

Ben, in that demo are you turning something with your foot?

No, just trying to control the angle of my shadow. I'm still getting the hang of this thing, there's a learning curve, lol. I have since replaced the blue LED with a super bright white LED and it works much better now, the light reflects off the bottom of my shoe and back down on the LDR really good, even in a pitch dark room

It is funny how misinterpreting something can lead to a new crazy idea.  I'm now wondering if a stomp switch can be mounted in a bearing of some sort, allowing it to turn and control a pot (or rotary encoder) underneath, kind of like a push-pull pot, but better.     (would probably put a small o-ring under the stomp cap to get it to grip the bushing better when pressed down.)

[jonboper]

So, as supplied by several of you here, thank you kindly, the wiring that ended up working for me was this:



To those who said not to bother with the attack pot, you were probably right. I tried a 25KB pot and only about 5% of it does anything, beyond that is too much resistance, so I will replace with a 2KB when I get one, which will offer some usable range...maybe. Thanks for all the help.

[wavley]

yr attk pot is missing a connection, to something. are you trying to do a burst/momentary override of a pot setting?

more info please.

He'll be needing a big copper coil thing and this thread http://www.diystompboxes.com/smfforum/index.php?topic=76932.0

Sorry, had to do it.

[jonboper]

Actually, after playing with it for an hour or two today, the attack pot is great. There's a sweet spot where if you hold it down it just borderline oscillates, makes a ton of great noise. I think I'll make it a 2.5-4KB pot with a parallel resistor at some point (beyond that it doesn't do anything). But I like the extra control, some might like it simpler.

@wavley, that post was pretty funny, I get it.

[Chrisfromiowa]

Quote from: Ben Lyman on September 30, 2017, 11:45:23 AM
Quote from: jonboper on September 30, 2017, 10:51:36 AM
Ben, in that demo are you turning something with your foot?
No, just trying to control the angle of my shadow. I'm still getting the hang of this thing, there's a learning curve, lol. I have since replaced the blue LED with a super bright white LED and it works much better now, the light reflects off the bottom of my shoe and back down on the LDR really good, even in a pitch dark room
It is funny how misinterpreting something can lead to a new crazy idea.  I'm now wondering if a stomp switch can be mounted in a bearing of some sort, allowing it to turn and control a pot (or rotary encoder) underneath, kind of like a push-pull pot, but better.     (would probably put a small o-ring under the stomp cap to get it to grip the bushing better when pressed down.)




Like a track button from an IBM laptop or an old arcade machine controller, but instead of having it translated into movement it would control two variables.

[EBK]

Like a track button from an IBM laptop

You mean this thing?


I'll admit, I always referred to these using very very informal terminology.