chirping tubescreamer ! ?

[gez]

back in the thread Paul suggested larger values for c16 &17

Try making C16 & C17 smaller to speed up switching (which is what Paul was suggesting a few posts up).  Can't hurt!  

[bluedreamin]

Hey ...now we're talkin , that made a big difference ! Now it only has the slightest noise and only when switching it on and if I touch both legs of one of the .01 caps I put in with my finger , essentially shorting it , there is no noise at all ! ! Very strange ! Sounds like we're pretty much there you guys but I can't help but wonder why this happened , a flaw in the circuit ?

[Paul Perry (Frostwave)]

I think it is another of those cases where fets have such a wide characteristic range, that you can build a dozen units & then BANG! you are bit on the ass, because one turns on at 2v and the others were all between 4 and 6v. That's why i have never used a fet as a voltage controlled element in any of my designs! (mind you, they make a great source follower buffer!).
The bigest source of unhappiness, in copying circuits from others, is when a "normal" variation in a component leads to a crap result, even though all the connections are right. And, it applies to some published circuits too! and even commercial ones, as we have just seen. This is one of the ways EEs earn their living, they look at a circuit & say"what is the WORST that can happen?" whereas most of us just SEE the 'worst' happen
Funnily, I woke up this morning thinking "hope i don't die without knowing why the tubescreamer chirps" i guess if this is my main worry, things are OK.. hell, I don't even HAVE a TS!

[bluedreamin]

LOL ! Now you and I can sleep ...and wake up knowing "why the tubescreamer chirps" LOL ! Thank you and all the others , it has been a long , strange trip indeed . I believe I will try my hand at modding this little pain in "OUR" ass ! Probably will be hearing from me again ! ...Don't be afraid , this looks easy ! Thanks all again !

[gez]

Now it only has the slightest noise and only when switching it on and if I touch both legs of one of the .01 caps I put in with my finger , essentially shorting it , there is no noise at all ! !

The caps are there to turn the FETs on slowly (well, slowish), which avoids clicking noises during switching.  It's best to leave them in there for this reason and find some FETs that will work in the circuit instead (there are suggestions in one of those threads I linked to).  Unfortunately it's a case of buy a hand full and stick them in there until you find ones that work.  Or (better still) do some testing).

Hats off to Paul for diagnosing this one!  One of those things that's obvious when it's pointed out to you, but I'd never have thought of it.