Jenny Greenteeth: LFO won't wobble

[KarenColumbo]

After many misadventures I thought I'd try a chorus again.
I decided to have a go at ValveWizard's "Jenny Greenteeth": http://valvewizard.co.uk/jennygreenteeth.html

I breadboarded it and it works - kind of. 

The triangle LFO just does a circle now and then - other than that nothing moves. If I touch the pots and wiggle them a bit, you can hear the modulation, but it's erratic and does not do it's thing by it's own.

So I took another BB and breadboarded just the LFO a second time. Same thing.

- I double and triple checked the schematic and my breadboarding - I took both schematics (which don't really show differences) at VW's site as reference. Everything where and what it should be
- My 9V and 4.5V are nearly perfect, 5V is regulated and 5V.
- I know ... breadboards and other diseases. So I connected those +9Vs and GNDs two and three times redundantly
- If I play palm mutes, there is a distinctive slapback delay there - I tried 4 PT2399s, they all work the same. So this is okay, too.
- I tried 3 different TL062s, a few TL072s and a 5532 in the LFO circuit to be sure. Slightly different sound colour, but same symptoms.

I guess the LFO is to blame. I know that ValveWizard is what his name suggests, so there must be something I overlooked.

Did some of you experience such woes, too?

Does somebody have a schematic for an LFO that's works here AND likes single supply power?

[Kipper4]

Quick test does the lfo work.
Stick an led between the depth pot lug and 4k7 to gnd.

[KarenColumbo]

It gets brighter when I turn up the "depth" pot. And when I wiggle the pots it changes brightness erratically

[Kipper4]

So Is the rate pot attached?

[KarenColumbo]

Curious thing: When I disconnect the LFO out (the pot's wiper) from the latch up circuit BC337's base, the LED I connected from the wiper to ground to test the LFO does all the LFO ramping. But it does nothing when the pot's wiper is connected as described in the schematic.

So I thought, frig it, and mixed up an anti-lockup-mode like in the Dimension D Chorus, but connected the pot's wiper directly to Pin 6 of the PT2399. Now I have chorus, but it's only usable when the "depth" pot is at it's minimum to, let's say, 2% of the wiper's way.

[KarenColumbo]

Thing is: When I move the Depth pot more than 2-3 % I have extreme pitch shifting

[Kipper4]

Thing is: When I move the Depth pot more than 2-3 % I have extreme pitch shifting

Bonus. So you just made a pitch shifter.

Congratulations.

[KarenColumbo]

Yeah Pretty New Age Atonal Swirling. Not my flavour.

But it works with two small changes: The ground lug of the depth pot lost it's 4k7 and goes directly to ground. And the resistor before the pot is now 30k - now I have a bit more usable room.

[PRR]

> I guess the LFO is to blame.

That is an extremely well-proven LFO. If it isn't wobbling, blame goes to the builder.

[KarenColumbo]

Yeah, I do blame myself. Working now, but mysteriously so - wish I new what did the trick and why it wont do as expected.

[duck_arse]

hey Karen, what transistors were you using when it wasn't working, BC337?

[KarenColumbo]

Yeah, i tried with those 337, but I couldn't get it to work. So I did a mash-up of this anti-lockup and the one from the genius "dimension p" chorus witgh 3904. Which worked. But I guess it wasn't the lock-up thing but some shit going on on the breadboard. I got it going, but it stopped working some hours ago. After a lot of tinkering, so I'm to blame, of course. There was some strange things going on - I simply don't get what's going on between the LFO's output (voltage swing?) and the "VCO" input at pin 6 of the PT2399. By the way: "Dimension P" sends the LFO's output to pin 2 of the PT2399 instead of pin 6 and "shunts" pin 6 (couples?) to ground through a big polcap.


I so wish I knew what I'm doing ...

It's a thing with me and chorus. I'm so 80ies, it hurts And a keyboard player, too.
Well, tomorrow new day, new luck. Have quite a handful of MN3XXXs to try this branch, too, but I fell in love with the "shimmer" of the Greenteeth thing. Ah, well. It's 9.30 PM here, gotta rise my carcass in 7 hours - a brew or two and BBC's Poirot will set me right

Thanks!

Edit: Just ordered a handful of these here: http://electricdruid.net/product/vclfo-10/ So I can give up worrying about the LFO. I always wanted a sine wave there

[ElectricDruid]

Wow, the Greenteeth is described as a "weird chorus" even before you start adding a multi-waveform LFO with several weird waveforms to it! Some of the more curvy sine-based stuff is probably pretty good for chorus and the random waveform might be nice too. Noise, spikes, and quad pulse are probably "experimental" in character...ahem.

Do let us know how it goes. I haven't tried that LFO with anything chorus-based yet.

Enjoy!

Tom

[KarenColumbo]

The way it worked (for some hours) on my breadboard, there was nothing weird to it - well, I "tamed" the intensity a bit, but it was shimmering, throaty, everything MY chorus should be. Perfect for those Joni Mitchell chords, lots of 9th and 11th in them Only thing that I didn't like was a bit of "pulsing" -> triangle LFO. If I EVER be able to reproduce it I'll try those waveforms Looking forward to receiving those multi-legged beasties

[KarenColumbo]

Well, I managed to reproduce it. I think that the breadboards I bought are sh%&/. But it works.

Now: I'd love to double the fun. I bb'd a second one. Could you gents kindly tell me where to connect both? Is this the right places? Or should I connect the second one directly to the input and output buffers?

And: should I decouple it with caps?

Please help - I can see light at the end of the tunnel already

[duck_arse]

[message sent .....]

[KarenColumbo]

[and answered. thank you sir]

This must be the most 80ies chorus that ever was. Steely, metallic, but (I spliced in a high pass) most transparent, a real cosmic thing. Thank you ValveWiz!