Another Nurse Quacky not quacking

[bancika]

I just finnished NQ build and I can't make it quack. As someone suggested I used opamp NE5532 with BC549 tranny. With that combination I only get slight volume drop, more bass and just little envelope following "thing" going on. I tried swapping with 4558 but there's even more volume drop and no envelope following. I used two 3mm red diodes (not matched, I just got two at store), one is on all the time and other follows playing (at higher range setting, at lower I can't see it)
Any ideas?
Thanks!

[343 Salty Beans]

http://www.elixant.com/~stompbox/smfforum/index.php?topic=29816.0

Follow that link, list voltages, and we can help you out a bit more.

My ideas?

First, make sure the NE and 4558 pinouts are the same.

Second, check for bad solder joints, etc. Check GEO's Debugging page for more info on simple debuggings. I wasted an hour of my time checking voltages and rebiasing a tranny only to find that I missed a connection entirely.

[Transmogrifox]

Just for kicks and giggles, hook up a 10k pot with the legs to +9V, & ground.  Connect the wiper to the 22k resistor at the base of the tranny.

Vary the pot and see if the filter changes in a more notable way than what you currently hear.

I'm betting that the tranny is biased on a bit and the filter start frequency is a bit higher than what would be acceptable.

If that's true, then you'll need to perhaps use a pot to bias the envelope following op amp.

The op amp type is not going to make a difference between "works" and "does not work".   It is typically something simple that you overlooked, or just a misbiasing problem on the tranny.  By "misbiasing" I don't mean it's a mistake you made, but I mean that NQ is a finickey circuit that gives trouble to most anyone who tries to build it.  When I built it on my breadboard, I had to do some fine tuning to make it work correctly.  In theory, it's simple enough that there is little that can go wrong, but the one or two things that can go wrong typically do.