This one is a bit unusual in as much as I’ve already built it and verified it as working. Here’s a vero layout for Tim Escobedo’s Wobbletron, I believe it’s a vibrato-thingy similar to what can be found in some old amps.
The original schematic (search for “tim escobedo wobbletron schematic”, I’m sure you’ll find it) called for a J201, which I have plenty of. Problem was not a single one worked.
So I tried a few 2N5457s and found two that gave a slight wobble. What really worked (almost too well) was a J112 (all of the ones I had gave lots of wobble). Experimenting for a while I came to the conclusion I wanted to stick with the J112, but greatly lower the 220K resistor between “Depth 1” and ground. Since the 2N5457 required a larger resistance here I figured I’d make it a trimpot.
Insert J112 (or 2N5457, or some other JFET maybe), set frequency fully clockwise (faster) and depth fully counter clockwise. Now adjust trimpot to where you want your depth minimum setting to be (probably at no, or very slight wobble). Now you can try playing with the range of the depth pot; I had good results with a B250k, but maybe something smaller/larger will work better with your JFET.
Anyway, good luck 🙂
As far as I remember the one I built works fine, including the depth control. I haven’t yet boxed it up, as I originally tried to house it in a 1590A, and something shorted to ground when I closed it up. It’s still in my pile of “will get to this eventually”.
I think I put all the info regarding what transistors etc. in the post, but it has been a while now.
Hello, I’ve been searching high and low for someone who actually build a Wobbletron successfully. I’ve made one, following the schematic, except I have a variable resistor between depth 1 and ground that is set to about 220K — but I can’t get the damn depth control to work. I only get wobble with depth full on (no resistance) as soon as I dial it back even slightly all wobble goes away … I’ve tried both linear and logarithmic pots but the result is the same.
Any ideas?
I’ve ordered some J112’s after reading this article I am still waiting for them to arrive — and I hope they will be my solution.
Yes, I tried a bunch of J201s too, but none of mine was any good either. So I went through all the other JFETs I had in my box and finally settled on the J112. Not to say that’ll work for you, only suggesting that you try different ones too.
The original schematic (search for “tim escobedo wobbletron schematic”, I’m sure you’ll find it) called for a J201, which I have plenty of. Problem was not a single one worked.