This one is based on a schematic by generalguitargadgets which originally calls for a rather odd 5-legged dual optocoupler, the VTL5C4/2. I figured I’d make a layout for two single optocouplers instead, but I don’t know how well it will actually work out. You’re obviously going to have to try different ones to find ones that work well.
Update (18.12.2012): Finally got this thing working. Tried lots of different optocouplers; two VTL5C4 didn’t work at all which was what I was hoping for first, but settled on a pair of NSL32. Lots of quacking, but there’s a hint of distortion in there as well, almost as if the IC is slightly mis-biased or is struggling with a bad load. I also note that the VTL5C4/2 optocoupler problem was solved a bit differently (and somewhat cheaper) over at www.beavisaudio.com by placing a single optocoupler across both 220k resistors. That might be a better solution that this layout, but I don’t know. Getting a bit tired of sensitive envelope filters using opto couplers, hehe.
Anyway, I would personally try building one of the other envelope filters out there.
Wish I could give you an answer, but this is above what I currently know about electronics so I’d only be guessing.
So I assume change to TL022 has no effect, the problem is the optocoupler. I hunt NSL32 with no luck, instead I bought some led. But all of them resulting clean sound :(. I’m curious why led D3 is always brighter than D4? Shouldn’t it equal? Thx
The TL022 will be drawing less current, but all of the ones you mention should be compatible. Had to look through my post to figure out how I ended up building this, and looks like I ended up using NSL32 optocouplers, but was never really happy with them.
Hi Harald, I’ve just finish built it. I can’t find TL022 nor TL062, so I use TL072 and also I use 5mm red led, but I think it’s not working properly, the wah sound come up so thin only in certain position of level and range pot (I use both 100K linear). So my question: is it will be much different if I change IC to TL022, and what kind of led do you use?
Thanks
Nice! I’m hoping you get it to work properly. Do continue to let us know how it goes 🙂
Built this up and it works, kind off, a bit too bright sounding and a bit twangy. Almost there but I think I’ll need to play about with some ldr/led combo’s, I used white high brite LEDs and they’re possibly giving too much light , I’ll report back once I experiment a bit more.
🙁
Sorry, I tried all LDR´s I had at home, but had no success!
Hi Dave – just wondering if you had any luck getting it working?
Thanks for giving it a try. I’m thinking the big challenge here is getting the right optocoupler. And it may not even work the way I’ve split it into two parallel optocouplers.
To be honest I have no idea what optocoupler would be good for this, but since the GGG project specifies the VTL5C4/2 maybe you’ll be good trying two regular VTL5C4?
I built it yesterday, but unfortunately it´s not working! I´m checking it again in the next days, maybe I get it to work! I tried a Tl072 and a Tl062 instead, but i can´t image that this would be the problem!?
Awesome, thanks Harold – I might give this one a shot if I get some free time over the next couple of weeks.
Do you know if this is the sort of optocoupler that would be required? http://australia.rs-online.com/web/p/optocoupler/2508981200/
Or are you better off with some LDRs and some heat shrink for this one?
Thanks!