Wobble Box Chorus/Vibrato

[Ripthorn]

I created this project while messing around with the ES56033 chip that I used in my Stalker Double Tracker project. I figured out a way to get some modulation, but the chip seems to have an internal compensation circuit, which means you can't control delay time the same way you can on PT2399. However, it still results in a fun little project with some weirdness to it. You can get a walk through of the whole circuit along with all the build documents at my little webpage for it: https://scientificguitarist.wixsite.com/home/wobble-box. This project is free for personal, non-commercial use. Enjoy!

[Radical CJ]

Some very extreme settings possible with that! as well as some almost conventional sounding 80s chorus. 

[Ripthorn]

Yeah, I spent quite a bit of time dialing in the range so it could be almost subtle all the way to "I might use this for one small part on one song" . Thanks for the listen!

[pinkjimiphoton]

just got my chips in, bro... lookin forward to building the board ya sent me!
its funny, was researching this, found an old thread where i suggested this chip back in 2014 and forgot all about it! kinda cool for no particular reason.
anyways.. if/when i get it done, i'll let ya know my thoughts, thanks again!

[iainpunk]

wow, why haven't i seen this thread before? that sounds awesome!
i think its more rotary speaker like than most other chorus/vibrato sounds, which i really like, since i'm not a huge fan of ''80s chorus''
if i have some cash again, ill buy the chip and throw it on some perfboard. i'll probably change the LFO to a simpler type, where i can determine the ramp up and down separately.

cheers

[Radical CJ]

I'm also curious about the apparent complexity of the LFO, and particularly the role of the third opamp connected to the tranistor. As a contrast, the LFO on Merlin's Jenny Greenteeth Weird Chorus (which uses a PT2339) seems a little bit simpler and to be doing a similar thing. As here
http://www.valvewizard.co.uk/jennygreenteeth.html

(Note that the schematic in the link above is probably not 100% correct, as I think the inverting and non-inverting inputs of the LFO's first opamp should be the other way around for it to work)

[Ripthorn]

The third opamp after the LFO is a current sink. The way that most digital delay chips work is by sinking current at a constant voltage. This is what the variable resistance on pin 6 of a PT2399 is doing. Using the LFO output, buffering it, and connecting to the transistor causes the transistor to work as a variable resistor, so the resistance seen on the pin to ground is constantly changing. This constant change is what causes the pitch shifting behavior.

On a PT2399, the LFO can be connected directly to pin 6 for modulation, but on the ES56033 the set up is different. I think there is internal compensation which means that sinking the current has to be done in this way.

Really any LFO fed into the current sink should work, I simply chose this one because it was a similar topology to one I have used before. I did modify it some on the breadboard and liked where it ended up.

[Radical CJ]

On a PT2399, the LFO can be connected directly to pin 6 for modulation, but on the ES56033 the set up is different. I think there is internal compensation which means that sinking the current has to be done in this way.

I'm glad you told me that. I don't have much spare time at the moment, but I did just get a few ES56033s in the mail, so at some point soon I will be breadboarding with them, and trying to modulate them.

I saw with your Stalker effect, they can do quite a delay time for double tracking (unlike a PT2399), have you ever tried using that effect on vocals? Iimagine it would sound like Ozzy Osbourne's vocal tracks in the 70s.

[Ripthorn]

Have not used it on vocals yet. I've got a modulated delay with this chip all designed, just waiting to finish another design or two before ordering prototype boards and building them up. It's a great little chip!

[pinkjimiphoton]

hey brian,
i finally got an enclosure in to do this up today. built it up, fired right up, really nice clean layout in a 125b. well done!
sounds just like it does in your demo.
its weird, but weird in a GOOD way. gotta change out the rate pot for a c taper someday, got an audio taper in there now cuz it was on hand.
was thinking... ya know, if the amount of the current sink <which i assume is what makes that cool wobble> were under envelope control, that would be a really cool and toneful addition to this cool circuit.... like, the harder ya hit it, the deeper the wobble, or the faster.
whatever, very cool toy, thanks man!
a couple for the photo album

obligatory porn glamour shot, 3d and black light friendly


utzgay






i love the copper hammertone. it makes the pedal sound even better. mojo, don't ya know