Fulltone OCD: high pitched feedback/sqeel with gain up past 4 o´clock

[pnadora]

Hallo,
I recently builded a OCD Vers. 3 from this layout: http://tagboardeffects.blogspot.de/2012/02/fulltone-ocd-all-versions.html

At first I thought is was fine becasue it sounds like it should and the knob and the switches work as intended. But then I turned up the gain higher and there is a high-pitched feeping noise with the gain past 3 o clock. Like a feddback. I can filter it out with the tone knob, but thats not a very good solution. It is significantly louder in the HP mode (guess thats some kind of tone/presence effect and has nothing to do with the source of the feedback)

I switched out the IC and the transistors but that did not help!

I already checked the board for bridges etc. and its fine.

Thank you all very much for any help!!

[Beaker]

Have you boxed it yet, or is it on a test rig?

If your board is completely error free, it could be a wire management problem. Try moving some of the wires around and see if things improve or get worse. Noise from the 9V power wires crossing over to your signal wires is sometimes a problem with high gain pedals. Shielded cable usually sorts things out.

[pnadora]

It is wired into the box already..
I am switching out my wires to shielded ones at the moment. Already have the Input, Output to the switch, the 9v to the board and the Input from the switch to the board changed and I think it got better. It gets tougher to solder at the moment, but next I will switch out the cables to the gain knob...  

I disconnected the tone knob to get an unfiltered version of the problem and it feeps even with the gain at low levels (the pitch gets lower with more gain so I think th etone knob just filtered it out at low gain levels even with the tone set high)

One thing I read in the comment to the schematic was that someone switched out the filter capacitor in the gain feedback loop to a higher valu eand the feeping stopped for him. It changes the tone though so I dont really want to do it. But I asked myself if maybe mine just has a really low value but in the tolerance (maybe fulltone measures their caps to have them high enough). Could that be a reason? I would switch the 220p on the left side of the IC to a 270p in that case (dont have small value caps at the moment though :/)

Thank you for the tip, I will let you know if it worked out in the end.

[pnadora]

Update: Shielding the wires did only improve the squeeling a little bit. I found an 330p (juhuu) and swithed the 220p on the left side of the layout (IC pins 1 and 2) and the sqeeeling went away :)

I cannot hear the sound difference so it stays that way :)

[Frank_NH]

What IC are you using?  I found that my OCD squealed unless I used a TL082.  Also, try increasing C3 to 47uF or higher (you can connect it in parallel to the existing 10 uF cap).

One thing to note about the OCD.   The op amp clips, and can clip very hard.  Some ICs are better than others at clipping (particularly those that use BJT transistors like the NE5532) so you may want to experiment.